Digital Needle Valve in vacuum gauge calibration device Integrating a digital needle valve in a portable vacuum gauge calibration device in order to reach the field calibration of vacuum gauge, based on static comparison method calibration technology. This article focuses on a technical scheme using a miniature digital needle valve and an upstream and downstream two-way gas flow control mode, combined with dual-channel high precision. The use of digital needle valve with a vacuum PID controller can solve the problem of field calibration and portability under the premise of precise vacuum control. 1. Question As a vacuum sensors or vacuum gauges are widely used in many fields and require regular calibration, the calibration device of vacuum gauge is a complete measurement system including a vacuum standard, a vacuum pump, a vacuum valve and a connecting pipeline. Its size is generally large and inconvenient to move, and is mostly fixed in the laboratory. Most existing vacuum gauge calibration methods are to remove the vacuum gauge used on field inspection. To meet the needs of field calibration, the following issues need to be addressed: (1) Reduce the size of related components, making the vacuum gauge calibration device easy to carry. (2) Adopt numerical control and digital needle valve to improve the precision of gas flow regulation. (3) Improve the vacuum degree control method and vacuum degree control accuracy and stability. In order to reach the field calibration of vacuum gauge and portability of calibration device, based on the static comparison method calibration technology, this article will focus on a technical scheme using a miniature digital needle valve and an upstream and downstream two-way gas flow control mode, combined with a high-precision vacuum PID controller. It can solve the problem of field calibration and portability under the premise of precise control of vacuum degree, and the fluctuation of vacuum degree can be controlled within ±1%. 2. Portable vacuum gauge calibration device technical scheme The entire structure of portable vacuum gauge calibration device is shown in Figure 1, which is a schematic diagram of a typical structure of the calibration device in the vacuum range of 0.1~760 Torr. The details of the plan are as follows: (1) Using the method of comparative static analysis, the calibrated vacuum gauge is compared with the reference standard vacuum gauge. The reference standard vacuum gauge uses two capacitive film vacuum gauges to cover the entire vacuum calibration range, refer to the standard vacuum gauge also acts as a vacuum control sensor. (2) The vacuum degree controller adopts a two-channel high-precision vacuum degree controller. The A/D of controller is 24 bits, and the D/A is 16 bits, which can correspond to high-precision signal output of capacitive film vacuum gauge and meet the vacuum degree control accuracy requirements. The two channels of controller correspond to the input signals of two vacuum gauges and the precise adjustment of air intake and exhaust flow of two-way digital needle valve. In the process of vacuum degree control, the two-way sensor signals can be automatically switched as required to reach programmable automatic control within the full range. The controller has PID self-tuning function and standard MODBUS communication protocol. (3) Two digital needle valves are used to adjust the air intake and exhaust flow respectively, and the controller adopts a bidirectional mode to adjust the two needle valves respectively. The air intake needle valve is mainly adjusted in the rough vacuum range, and the air intake needle valve is mainly adjusted in the high vacuum range. When the vacuum degree is constant in the full range, the vacuum degree fluctuation rate can be controlled within ±1%. Further information on the digital needle valve, please visit: https://www.genndih.com/proportional-flow-control-valve.htm

Abstract: In glass blow molding process, there always exist problems such as poor consistency and low yield of finished products due to unstable air pressure of manual blowing and machine blowing. In order to solve these problems, this article focuses on a full-automatic control solution for blowing air pressure using high flow rate version of electronic flow control valve, so that the blowing air pressure can be quickly and precisely controlled according to the set curve, which can greatly improve production efficiency and product yield. 1. Question Glass is an amorphous solid. Glass products need to be softened by heating and blow-molded during processing. However, the current glass blow-molding process has the following problems that need to be solved: (1) In most of the current glass blow molding process in which air is blown into the interior of glass products by manual mouth blowing, it is necessary to rely on people to blow air with a pipe and then shape the molten glass. This method greatly increases the burden on producer, easily causes dizziness due to lack of oxygen in brain, and reduces work efficiency at the same time. The finished products produced by this process have poor consistency and low yield. At the same time, the production cycle of glass products is prolonged, which is not conducive to widespread promotion and popularization. (2) In the glass blow molding process, since the wind has been acting on the bottom of glass bottle after it comes out of the blow molding tube. The blowing pressure is not uniform, which will lead to different thicknesses of the bottom of glass bottle after forming. In the process of blow molding, the plastic device will have unstable air pressure, and it does not have the function of automatic voltage stabilization, resulting in different quality levels of glass bottles. By analyzing the glass blow molding process of existing glass products, it can be found that the entire blow molding process is a typical air pressure change process in a small closed space. If this air pressure change process can be precisely controlled and the air pressure change process can always be accurately repeated, then realize the automation and quality reliability of glass blow molding process of glass products, greatly improve the yield and shorten the production cycle. 2. Technical scheme The basic principle of automatic control of blowing pressure in glass molding is to quickly control the air pressure in a closed chamber as required, and use this air pressure to replace the pressure change during manual blowing. The shchem of the entire control method is shown in Figure 1. The automatic air blowing pressure control device mainly includes a chamber, an electronic flow control valve, a pressure sensor, a PID controller and a high-pressure air source. The precise control of pressure in chamber adopts the dynamic control method, that is, according to the pressure. The measured value of the force sensor is compared with the set value, and the PID controller adjusts the intake flow and exhaust flow at the same time, so that the pressure in the cavity quickly reaches a dynamic balance and controls the pressure at the set value. The set value can be a constant pressure point that does not change with time. It can also be a curve of pressure changing with time designed according to the requirements of glass molding blowing process, so as to meet different pressure requirements. In a word, through this technical solution, the automatic and precise control of blowing pressure of glass molding can be reached, and the control accuracy and repeatability can be ensured, so as to ensure the product quality and stability. For further information about the electronic flow control valve, please visit: https://www.genndih.com/proportional-flow-control-valve.htm

Superconducting Gravity Instruments – Ultra-Fine Temperature (0.1mK) and Pressure Control Solution The temperature of liquid helium pool is required to be constant in the ultra-low gravity instrument. In order to reach the fluctuation degree of less than 0.1mK, the fluctuation degree of air pressure control should be less than 10Pa. For this reason, this article focuses on a corresponding technical scheme in superconducting gravity instruments. The core content is to reach the precise control of air pressure of buffer tank. The bidirectional control mode is adopted, and the air pressure sensor, electronic needle valve and PID controller with a precision of 1/10,000 are used. 1. Question Superconducting gravity instruments include superconducting gravimeters and superconducting gravity gradiometers, both of which are used to precisely measure gravity signals. Superconducting gravity instruments need to measure extremely weak signals at low temperature, so there is a high requirement for constant low temperature, that is, the temperature fluctuation of liquid helium pool is required to be within 0.1mK. The precise control of temperature of liquid helium pool in superconducting gravity instruments can be reached by controlling the air pressure in liquid helium pool, which requires the measurement and control of air pressure to reach a very high level. In this article, a corresponding solution is proposed for the high-precision control of air pressure in liquid helium cell in the superconducting gravity instrument. The advantage of this solution is that the control accuracy of temperature of liquid helium pool is mainly affected by the accuracy of pressure sensor. The ultra-high-precision pressure sensor is selected, and the downstream pumping flow control mode is adopted through the precise numerical control needle valve and the high-precision PID controller. The fluctuation of liquid helium temperature is stably controlled within 0.1mK. 2. Technical Scheme The precise control principle of liquid helium temperature in superconducting gravity instruments is based on the relationship between the saturated vapor pressure of liquid helium and the corresponding temperature. According to the corresponding relationship between the saturated vapor pressure of liquid helium and the temperature, the temperature of liquid helium should be controlled at about 4K, and the temperature fluctuation should be less than 0.1mK. When the upper pressure of liquid helium should be controlled at about 100kPa, the fluctuation of pressure should be less than 10Pa. In order to reach the above air pressure control accuracy, the technical solution proposed in this article specifically in superconducting gravity instruments includes the following aspects: (1) The air pressure control in the upper part of liquid helium pool can be abstracted as the pressure control in a closed container. For the pressure control of the closed container, it is necessary to add a buffer tank, through the pressure control of buffer tank. The system reaches the pressure control of liquid helium pool, and the structure is shown in Figure 1. (2) The pressure control of buffer tank adopts the upstream and downstream two-way control mode, which is controlled by adjusting the flow of air intake and exhaust. (3) The whole control system includes buffer tank, air pressure sensor, PID controller, digital needle valve and vacuum pump. (4) If the air pressure is controlled at 100kPa and the fluctuation is required to be less than 10 Pa, the measurement and control of the air pressure are required to have an accuracy of 10/100k=0.0001 (one ten thousandth), so it is necessary to be equipped with a precision of one ten thousandth Barometer and PID controller. In short, the control accuracy of technical solution described in this article is mainly limited by the accuracy of air pressure sensor and the PID controller. Combined with the small flow electronic needle valve driven by the stepping motor, the superconducting gravimeter can be reached through the high-precision sensor and controller. Precise control of liquid helium temperature, temperature fluctuation can be controlled within 0.1mK, and is not affected by changes in external ambient temperature. For further information on the proportional flow control valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm

Rapid and Precise Control Technology of Vacuum Degree and Temperature in Vacuum Pulse Halogenation Process Abstract: Braised products are traditional food, and vacuum pulse process can effectively improve quality and shorten production time,and is more and more widely used in development and production of braised products. Focusing on the rapid and precise control requirements for the important process parameter of vacuum degree in the new vacuum pulse process, this article introduces the complete solution and implementation content in detail using FC series proportional flow control valve. 1. Question As a traditional and nutritious food, braised products are deeply loved by public and are instant food for leisure and tourism. The current braised product manufacturing process is mainly divided into two categories: traditional braised method and vacuum drying method, and the new vacuum pulse braised method have outstanding characteristics. Compared with traditional braised method, vacuum pulse braised method can not only shorten the braised period. It can shorten time from 8 hours to 80 minutes, greatly improve the production efficiency, retain the food flavor, and can also reduce the content of microorganisms by 4 orders of magnitude, thus the product safety is greatly improved. The typical vacuum pulse process is shown in Figure 1. The vacuum pulse process has high requirements on equipment and requires precise control of two important parameters (vacuum degree and temperature) in the braising process. The specific requirements are as follows: (1) Real-time measurement of vacuum degree and temperature can be reached at the same time, and precise control is implying according to the set program. Therefore, the controller needs to have at least two independent signal acquisition and control functions. (2) As shown in Figure 1, it is necessary to accurately control vacuum degree and temperature according to the upper and lower limits of setting vacuum degree and temperature and the corresponding change speed. This is equivalent to require the controller to have accurate program curve control capabilities. This article focus on corresponding solutions for the above requirements, and will introduce integrated vacuum and temperature controllers that can be used in vacuum pulse braised processes, and introduce corrosion-resistant FC proportional flow control valve driven by stepper motors for gas flow regulation, which can well meet the precise control requirements of vacuum pulse braised process. 2. Vacuum pulse braised process control scheme The vacuum degree and temperature need to be precisely controlled in the vacuum pulse braised process, and the specific control system implementation is shown in Figure 2. In the vacuum degree control process shown in Figure 2, a method different from the previous vacuum degree control method is adopted, that is, an air intake channel is added to the vacuum chamber, multi-channel controller and a numerical control needle valve with fast response time and high precision are used. This program has two outstanding features: (1) It can reach precise control of vacuum degree in the range of 0.1~1000mBar, and has a fluctuation rate of less than ±1% in the whole range. The specific implementation is that when the vacuum degree is less than 10torr, the control adopts the upstream mode; when the vacuum degree is greater than 10torr, the control adopts the downstream mode. At the same time, fast-response proportional flow control valves and controls ensure that temperature changes have minimal effect on vacuum. (2) The equipped 2-channel integrated PID controller can reach the simultaneous control of vacuum degree, temperature and tunable speed. 2 independent channels for vacuum and temperature measurement, control and display. (3) The host computer can communicate with the controller in real time to design, edit, store and load various vacuum degree and temperature control process curves. 3. 24-bit high-precision multi-functional controller In order to reach the precise control of vacuum degree, temperature and rotation speed in vacuum microwave drying, KaoLu has developed FC series 24-bit high-precision programmable PID universal controller, as shown in Figure 2. This series of PID controllers are very useful and cost-effective. The main performance indicators of VPC series controllers are as follows: (1) Precision: 24-bit A/D, 16-bit D/A. (2) Maximum sampling speed: 50ms. (3) Various input parameters: 47 input signals (thermocouple, thermal resistance, DC voltage) can be connected to various temperature and vacuum sensors for measurement, display and control. (4) Various output forms: 16BIT analog signal, 2A (250V AC) relay, 22V/20mA solid state relay, 3A/250VAC SCR. (5) Multi-channel: independent 1-channel or 2-channel output. 2 channels can reach simultaneous measurement and control of temperature and vacuum degree, and the alarm output channel can be used to control the start-stop of rotating motor. (6) Multi-function: forward, reverse, forward and reverse bi-directional control, heating/cooling control. (7) PID program control: The improved PID algorithm supports PV differential and differential advance control. It can store 20 groups of PID and support 20 program curves (50 segments each). (8) Communication: Two-wire RS485, standard MODBUS RTU communication protocol. (9) Display mode: digital hall and IPS TFT true color LCD. (10) Software: The operation of controller and the data acquisition and storage can be reached through the software computer. (11) Dimensions: 96×96×87mm (hole size 92×92mm). 4. Stepper motor drives corrosion-resistant high-speed needle valve In order to reach high-precision adjustment in the process of vacuum degree control, KaoLu has developed a series of proportional control flow valves with different flow rates based on the needle valve using stepper motors, as shown in Figure 2. The magnetic hysteresis of this series is much smaller than solenoid valves, and has a high-speed response within 1 second. In particular, the use of FKM sealing technology enables the valve to have superior corrosion resistance. The detailed technical indicators are shown in Figure 4 shown. Model FC-20 FC-120 FC-300 FC-1000 Valve type Needle Valve Spool Drift Diameter 0.9mm 2.25mm 2.75mm 4.10mm Actuator Bipolar stepper motor control Response time 0.8sec(Open to close) Standard size G1/8” G3/8” Fluid Inert gas and liquid Contact Materials Stainless Steel Pressure Range -1 ~ 7bar -1 ~ 5bar Maximum Flow 50L/min @7bar 240L/min @7bar 290L/min @7bar 600L/min @7bar   Linearity ±2% ±0.1 ~ 1% ±0.2 ~ 5% ±11% Repeatability (Full scale) ±0.1% Flow Resolution (Step length) 0.1L/min 0.1 ~ 0.2L/min 0.2 ~ 0.75L/min 1L/min Shift Resolution (Step length) 12.7um 25.4um Operating Temperature Range 0 ~ 84°c Seal Standard FKM or other choices of seals Control Signal DC: 0 ~ 10V (or 4 ~ 20mA) Power Supply DC: 24V (12W) (Figure 5 Technical indicators of KaoLu’s FC electronic needle valve) For further information, please visit https://www.genndih.com/proportional-flow-control-valve/mid-flow-proportional-valve-0-130L-min.html FC proportional control flow valve is equipped with a stepper motor drive circuit module, which provides the required power supply and control signal for FC proportional control flow valve, and converts the DC signal into step control of bipolar stepper motor, and can also provide RS485 direct control of serial communication. Its specifications and dimensions are shown in Figure 5. When using proportional flow control valve in vacuum microwave drying, open-loop control method can also be used to install needle valve at the front end of vacuum pump instead of electric ball valve, and the vacuum degree can be controlled by adjusting pumping flow, but the stability of this open-loop control method is poor. It is difficult to reach higher stability requirements. Therefore, it is generally recommended to use closed-loop control method shown in Figure 1, that is, to add an air intake control valve to vacuum chamber, and to achieve precise control of vacuum degree by adjusting air intake flow and exhaust flow at the same time. Using KaoLu’s proportional flow control valve can help with achieving the desired function.

Precise Control of Vacuum, Temperature and Rotational Speed During Vacuum Microwave Drying (VMD) Abstract: Focusing on the current local vacuum microwave drying technology research and equipment, the drawbacks are simple control equipment, poor vacuum degree control effect, and low product quality. This article proposes the corresponding solutions and integration of vacuum microwave drying using FC series pneumatic proportional flow control valve. The vacuum degree, temperature and speed controller of the type are introduced, and the corrosion-resistant pneumatic proportional flow control valve driven by stepper motor for gas flow adjustment are introduced, which can precisely control the vacuum microwave drying process. 1. Question Vacuum microwave drying is a new type of microwave energy application technology that combines microwave heating technology and vacuum technology. In the drying process of materials, the drying temperature range is generally 30~60℃, and vacuum degree range is generally 0.01~95kPa, which has advantages of high drying output, good quality, low processing cost and low energy consumption. In addition, when drying at low temperature and low pressure, the oxygen concentration is low, and the oxidation reaction of dried material is weakened and slowed down, thereby ensuring the flavor, appearance and color of material, and it is easy to dry heat-sensitive materials, especially for traditional Chinese medicine extracts, meat food, chemical raw materials, low-temperature drying of fruits and agricultural products has unique advantages. Since vacuum microwave drying technology utilizes the principle of lowering the boiling point of water under low pressure, and combines the characteristics of rapid, homogeneous and low energy consumption of microwave heating. Vacuum degree, temperature and rotational speed are the three key control parameters in application of vacuum microwave drying technology. In the current local application of vacuum microwave drying technology, there are generally problems such as rough control equipment, poor vacuum degree control effect, and low product quality, which are mainly reflected in the following aspects: (1) For different materials, the vacuum degree, temperature and rotation speed required in the drying process are completely different. The variation range of vacuum degree is very wide, such as from 0.01kPa to 95kPa, so it is necessary to have accurate measurement and measurement of vacuum degree in a wide range. For different vacuum degree needs different control methods. (2) The change of vacuum degree will have a serious impact on evaporation temperature, and temperature change after microwave heating will cause the rapid increase of vacuum degree. Vacuum degree and temperature are a set of variables that affect each other. In order to ensure product quality, the vacuum degree control is required to have a fast response time, so that vacuum degree in drying process is always constant and not affected by temperature changes, and the fluctuation rate of vacuum degree after homeostasis is small. Experiments have proved that the use of pneumatic proportional flow control valve can achieve the desired effect. (3) In addition to the need to control vacuum degree and temperature (microwave heating power) at the same time, in order to ensure the stability of microwave heating materials, it is also necessary to select and control rotation speed. (4) Because different materials require different PID control parameters and process parameters, the controller is required to have multi-program and multi-parameter storage functions, which are easy to call at any time during the process, so as to improve automation level of the entire drying process. 2. Vacuum microwave drying control scheme The vacuum degree, temperature and turntable speed need to be precisely controlled in vacuum microwave drying process. At present, the commonly used control schemes in Taiwan are generally relatively simple. The improved scheme proposed here is shown in Figure 1. In the vacuum degree control system shown in Figure 1, a method different from the previous vacuum degree control method is adopted, that is, an air intake channel is added to vacuum chamber, and a numerically controlled electric needle valve, or so-called pneumatic flow control valve, and high precision multi-channel controller with fast response speed are used. This program has two outstanding features: (1) It can reach precise control of vacuum degree in the range of 0.01~95kPa, with a fluctuation rate of less than ±1%. The specific implementation is that when vacuum degree is less than 10torr, the control adopts the upstream mode. When vacuum degree is greater than 10torr, the control adopts the downstream mode. At the same time, fast-response valves and controls ensure that temperature changes have minimal effect on vacuum. (2) Equipped with 2-channel integrated PID controller, which can reach simultaneous control of vacuum degree, temperature and turntable speed. 2 independent channels are used for the measurement, control and display of vacuum and temperature, and the alarm output channel can be used to control the speed of turntable or start-stop of rotating motor. 3. 24-bit high-precision multi-functional controller In order to reach the precise control of vacuum degree, temperature and rotation speed in vacuum microwave drying, KaoLu have developed FC series 24-bit high-precision programmable PID universal controller, as shown in Figure 2. This series of PID controllers are very useful and cost-effective. The main performance indicators of VPC series controllers are as follows: (1) Precision: 24-bit A/D, 16-bit D/A. (2) Maximum sampling speed: 50ms. (3) Various input parameters: 47 input signals (thermocouple, thermal resistance, DC voltage) can be connected to various temperature and vacuum sensors for measurement, display and control. (4) Various output forms: 16BIT analog signal, 2A (250V AC) relay, 22V/20mA solid state relay, 3A/250VAC SCR. (5) Multi-channel: independent 1-channel or 2-channel output. 2 channels can reach simultaneous measurement and control of temperature and vacuum degree, and the alarm output channel can be used to control the start-stop of rotating motor. (6) Multi-function: forward, reverse, forward and reverse bi-directional control, heating/cooling control. (7) PID program control: The improved PID algorithm supports PV differential and differential advance control. It can store 20 groups of PID and support 20 program curves (50 segments each). (8) Communication: Two-wire RS485, standard MODBUS RTU communication protocol. (9) Display mode: digital hall and IPS TFT true color LCD. (10) Software: The operation of controller and the data acquisition and storage can be reached through the software computer. (11) Dimensions: 96×96×87mm (hole size 92×92mm). 4. Stepper motor drives corrosion-resistant high-speed needle valve In order to reach high-precision adjustment in the process of vacuum degree control, KaoLu have developed a series of pneumatic proportional flow control valves with different flow rates based on the needle valve using stepper motors, as shown in Figure 2. The magnetic hysteresis of this series is much smaller than solenoid valves, and has a high-speed response within 1 second. In particular, the use of FKM sealing technology enables the valve to have superior corrosion resistance. The detailed technical indicators are shown in Figure 4 shown. Model FC-20 FC-120 FC-300 FC-1000 Valve type Needle Valve Spool Drift Diameter 0.9mm 2.25mm 2.75mm 4.10mm Actuator Bipolar stepper motor control Response time 0.8sec(Open to close) Standard size G1/8” G3/8” Fluid Inert gas and liquid Contact Materials Stainless Steel Pressure Range -1 ~ 7bar -1 ~ 5bar Maximum Flow 50L/min @7bar 240L/min @7bar 290L/min @7bar 600L/min @7bar   Linearity ±2% ±0.1 ~ 1% ±0.2 ~ 5% ±11% Repeatability (Full scale) ±0.1% Flow Resolution (Step length) 0.1L/min 0.1 ~ 0.2L/min 0.2 ~ 0.75L/min 1L/min Shift Resolution (Step length) 12.7um 25.4um Operating Temperature Range 0 ~ 84°c Seal Standard FKM or other choices of seals Control Signal DC: 0 ~ 10V (or 4 ~ 20mA) Power Supply DC: 24V (12W) (Figure 4 Technical indicators of KaoLu’s FC electronic needle valve) For further information, please visit https://www.genndih.com/proportional-flow-control-valve/mid-flow-proportional-valve-0-130L-min.html FC pneumatic proportional flow control valve is equipped with a stepper motor drive circuit module, which provides the required power supply and control signal for FC pneumatic proportional flow control valve, and converts the DC signal into step control of bipolar stepper motor, and can also provide RS485 direct control of serial communication. Its specifications and dimensions are shown in Figure 5. When using pneumatic proportional flow control valve in vacuum microwave drying, open-loop control method can also be used to install needle valve at the front end of vacuum pump instead of electric ball valve, and the vacuum degree can be controlled by adjusting pumping flow, but the stability of this open-loop control method is poor. It is difficult to reach higher stability requirements. Therefore, it is generally recommended to use closed-loop control method shown in Figure 1, that is, to add an air intake control valve to vacuum chamber, and to achieve precise control of vacuum degree by adjusting air intake flow and exhaust flow at the same time.

Rotary Evaporators: Integrated Controllers for Vacuum, Temperature and Rotation with Corrosion Resistant Digital Control Valves Abstract: At present, rotary evaporators can be built in different ways in various laboratories. In terms of vacuum control of evaporators, local customers generally require that they can replace the more expensive foreign vacuum control systems, improve the programming and automation level of vacuum control, improve the accuracy and stability of vacuum control, and solve the corrosion resistance of control valves. The problem even requires the use of controller to program temperature, vacuum and rotation at the same time. According to the improvement requirements put forward by users, this article focuses on corresponding solutions, and introduces related products such as high flow proportional valve especially used for evaporator temperature, vacuum degree and rotary motor control. 1. Users’ requirement A rotary evaporator is the common equipment in laboratory. Through the electronic control in evaporator, the solvent in flask is rapidly evaporated under the appropriate rotation speed, temperature and vacuum degree. The working vacuum range of general rotary evaporator is 1 to 760 mmHg (absolute vacuum). In specific applications, the vacuum level will be set and controlled according to the requirements of different mixtures. As simple common laboratory equipment, the rotary evaporator can be built by each one in laboratory, and there are also various specifications for ordering in market. For the rotary evaporators currently used in some user laboratories, users put forward clear requirements in the following aspects: (1) Some laboratories are equipped with imported rotary evaporators, but they also need to be equipped with higher-priced vacuum controllers separately, hoping to replace them with local products. (2) Local and self-built rotary evaporators are expected to be equipped with multi-functional and high-precision vacuum controllers to reach the programming and automation of computer control of test process. It is hoped that multiple sets of control process setting curves can be stored for direct recall. The computer sets the test program and displays the changes of entire control process. (3) At present, the vacuum control process of international and local rotary evaporators generally adopts the valve on-off or vacuum pump start-stop method. The control accuracy and stability are weak. It is hoped to use a high-speed digital proportional valve with continuously adjustable opening. (4) In recent years, high flow proportional valves in vacuum control devices of international and local rotary evaporators generally lack corrosion resistance, and it is hoped to use vacuum regulating valves that are resistant to corrosive gases and liquids. (5) For some self-built rotary evaporators, it is hoped that temperature control, vacuum control and rotation control can be integrated to reduce the complexity of instrument and its operation, and to improve the level of integration and automation. This article focuses on corresponding solutions for the above requirements, and introduces the integrated temperature, vacuum and rotation controller specially used for evaporators and the corrosion-resistant needle valve driven by stepper motor, which can meet the needs of different users of rotary evaporators’ test requirements. 2. Local 24-bit high-precision multi-functional controller In order to reach the test and program control of temperature, vacuum degree and rotation of rotary evaporator, KaoLu have developed the VPC series 24-bit high-precision programmable PID general controller, as shown in Figure 1. This series of PID controllers are very extraordinary and cost-effective. The main performance indicators of VPC series controllers are as follows: (1) Precision: 24-bit A/D, 16-bit D/A. (2) Maximum sampling speed: 50ms. (3) Various input parameters: 47 input signals (thermocouple, thermal resistance, DC voltage) can be connected to various temperature and vacuum sensors for measurement, display and control. (4) Various output forms: 16BIT analog signal, 2A (250V AC) relay, 22V/20mA solid state relay, 3A/250VAC SCR. (5) Multi-channel: independent 1-channel or 2-channel output. 2 channels can reach simultaneous measurement and control of temperature and vacuum degree, and the alarm output channel can be used to control the start-stop of rotating motor. (6) Multi-function: forward, reverse, forward and reverse bi-directional control, heating/cooling control. (7) PID program control: The improved PID algorithm supports PV differential and differential advance control. It can store 20 groups of PID and support 20 program curves (50 segments each). (8) Communication: Two-wire RS485, standard MODBUS RTU communication protocol. (9) Display mode: digital hall and IPS TFT true color LCD. (10) Software: The operation of controller and the data acquisition and storage can be reached through the software computer. (11) Dimensions: 96×96×87mm (hole size 92×92mm). 3. Stepper motor drives corrosion-resistant high-speed needle valve In order to reach high-precision adjustment in the process of vacuum degree control, KaoLu have developed a series of high flow proportional valves with different flow rates based on the electronic needle valve using stepper motors, as shown in Figure 2. The magnetic hysteresis of this series is much smaller than solenoid valves, and has a high-speed response within 1 second. In particular, the use of FKM sealing technology enables the high flow proportional valve to have superior corrosion resistance feature. The detailed technical indicators are shown in Figure 3 shown. Model FC-20 FC-120 FC-300 FC-1000 Valve type Needle Valve Spool Drift Diameter 0.9mm 2.25mm 2.75mm 4.10mm Actuator Bipolar stepper motor control Response time 0.8sec(Open to close) Standard size G1/8” G3/8” Fluid Inert gas and liquid Contact Materials Stainless Steel Pressure Range -1 ~ 7bar -1 ~ 5bar Maximum Flow 50L/min @7bar 240L/min @7bar 290L/min @7bar 600L/min @7bar   Linearity ±2% ±0.1 ~ 1% ±0.2 ~ 5% ±11% Repeatability (Full scale) ±0.1% Flow Resolution (Step length) 0.1L/min 0.1 ~ 0.2L/min 0.2 ~ 0.75L/min 1L/min Shift Resolution (Step length) 12.7um 25.4um Operating Temperature Range 0 ~ 84ºc Seal Standard FKM or other choices of seals Control Signal DC: 0 ~ 10V (or 4 ~ 20mA) Power Supply DC: 24V (12W) (Figure 3 Technical indicators of KaoLu’s FC high flow proportional valve) FC series high flow proportional valve is equipped with a stepper motor drive circuit module, which provides the required power supply and control signal for FC high flow proportional valve, and converts the DC signal into step control of bipolar stepper motor, and can also provide RS485 direct control of serial communication. Its specifications and dimensions are shown in Figure 4. For further information, please visit https://www.genndih.com/proportional-flow-control-valve/mid-flow-proportional-valve-0-130L-min.html When rotary evaporator uses a numerically controlled high flow proportional valve, the high flow proportional valve can be installed at the front end of vacuum pump by an open-loop control method, and vacuum degree can be controlled by adjusting the pumping flow rate. However, the stability of this open-loop control method is poor, and it is difficult to reach higher purity requirements. In order to solve this problem, a closed-loop control method can be adopted, that is, an air intake control valve is added to the evaporator, and the precise control of vacuum degree can be reached by adjusting the air intake flow and the exhaust flow.

Application of digital control valve in Precision Control of Vacuum Pressure in MOCVD Process Abstract: Focusing on problems existing in vacuum pressure control in the current MOCVD equipment and process, such as most equipment can only use the downstream control mode, the response speed of throttling valve is not enough; the corrosion resistance of throttling valve and the acquisition accuracy of pressure controller are not high. This article proposes corresponding solutions to improve MOCVD equipment and improve process and product quality. 1. Question In semiconductor industry, MOCVD has many remarkable features. It can be used for large area growth, can precisely control composition and thickness, has high repeatability and growth rate, can cover complex substrate shapes, can quickly switch gas paths to prepare steep multi-layer interfaces, suitable for original annealing, etc. However, in the development and process commissioning of MOCVD equipment, it is necessary to research and select production-related growth parameters, including reaction chamber shape, working pressure, growth temperature, base rotational speed, gas flow rate, and inlet temperature. The working pressure of MOCVD is generally in the range of 10 mtorr-500 torr. The precise control of working pressure determines the flow stability of reaction chamber, but there are still the following problems in the current vacuum pressure control: (1) As shown in Figure 1, the current MOCVD equipment basically uses the downstream mode to control working pressure, that is, install throttling valve at exhaust end to adjust the exhaust flow to reach pressure control in the reaction chamber, but this is only applicable to processes with higher pressure, such as working pressure range of 100~500torr. However, for the low pressure requirements of some processes, adopting downstream control mode will cause large fluctuations in working pressure, which cannot be accurately controlled, thereby affecting product quality. For the precise control of low working pressure, it is best to use upstream control mode, that is, to control flow at inlet end to stabilize pressure of the reaction chamber. (2) The MOCVD process is always with temperature changes, and temperature changes will seriously affect the stability and controllability of working pressure. Thus, it is required to reach accurate control of working pressure during temperature changing process, which requires air intake and exhaust. This requires that response speed of air intake and exhaust control valves is as fast as possible, and control valve should be controlled within 5 seconds from fully open to fully closed, preferably within 1 second. (3) Some MOCVD working gases are corrosive, and corresponding valves may have strong corrosion resistance to improve continuous and normal operation of the equipment. (4) At present, most of the controls use PLC modules, but very few PIC controllers can reach 24-bit analog-to-digital conversion accuracy. For the precise control of working pressure, it is recommended to use a 24-bit precision PID controller to apply completely to the high-precision measurement advantages of capacitive pressure sensors. Using KaoLu’s pneumatic proportional valve is also the best choice for customers. This article will focus on corresponding solutions for the above problems existing in the current MOCVD equipment and processes. For further information, please visit https://www.genndih.com/proportional-flow-control-valve/mid-flow-proportional-valve-0-130L-min.html 2. Pressure Precision Control Scheme Within the working pressure range of MOCVD, it is generally required that the working pressure in the reaction chamber can be accurately controlled and can stay constant at any set point within a certain range. In order to meet the precise control of different pressure ranges of low and high pressure, the proposed pressure control scheme is to add an upstream control mode to the original downstream control mode. The structure of vacuum pressure control system is shown in Figure 2, and the details are as follows: (1) Install KaoLu’s FC series pneumatic proportional valve driven by a stepper motor at air inlet and exhaust port of reaction chamber, respectively. The pneumatic proportional valve is directly installed at air inlet, and pneumatic proportional valve is installed between the exhaust port and the vacuum pump. For MOCVD equipment, an air cell can be added to mix the incoming working gas in proportion and then enter the reaction chamber through pneumatic proportional valve. When the control is performed under high pressure, the opening of pneumatic proportional valve can be fixed, and only the downstream pneumatic proportional valve can be adjusted; when the control is performed under low pressure, the opening of pneumatic proportional valve can be fixed, and only the upstream pneumatic proportional valve can be adjusted. This can meet the needs of different pressure control. (2) Both pneumatic proportional valve and electronic needle valve have high-speed throttling valves. The response time of pneumatic proportional valve is 0.8 seconds. The electronic needle valve has two response speed models, 5 seconds and 1 second. The valve body of pneumatic proportional valve and electronic needle valve is made of stainless steel, and the seal is made of FFKM perfluoroether rubber, which has super corrosion resistance and can be used for various corrosive gases and liquids. (3) In MOCVD, a capacitance pressure gauge with a range of 1000torr or 10torr is generally used for pressure measurement, and its accuracy can reach ±0.2%. A vacuum pressure sensor with a higher accuracy of ±0.05% can also be used for measurement. Therefore, a dedicated 24-bit A/D acquisition high-precision PID vacuum pressure controller is used in scheme to match the measurement accuracy of high-precision capacitive pressure sensor and ensure the control accuracy. In summary, through the implementation of above scheme, pressure fluctuation can be controlled within ±1% in the entire vacuum pressure range, and pressure can be quickly and constant in response to temperature change of reaction chamber, while the corrosion-resistant seal will greatly increase the life of valve. Therefore, KaoLu’s pneumatic proportional valve is the great choice for you!

Precision Control Technology of Vacuum in Micro-Displacement and Inclination Measurement of Michelson Laser Interferometer sensor Abstract: In the precise micro-displacement and inclination measurement of Michelson laser interferometer sensor, it is necessary to accurately control the degree of vacuum; otherwise it will cause huge fluctuations due to factors such as deformation, refractive index and temperature, and even make the measurement impossible. This article introduces the automatic control technology of vacuum level using electronic flow control valve, and introduces the specific implementation scheme in detail. 1. Question As a high-precision optical instrument, Michelson laser interferometer sensor has been widely used. It can be used to measure wave length, gas or liquid refractive index, thickness, displacement and inclination. It can measure length, velocity, angle, flatness, straightness and verticality of high-precision measurement, etc. However, in high-precision measurement, Michelson laser interferometer sensor will be seriously affected by atmosphere environment. For this reason, the measured object is generally placed in a low-pressure vacuum environment, as shown in Figure 1, and the degree of vacuum is precisely controlled with an electronic flow control valve, or it would cause the following problem: (1) Gas refractive index fluctuations in the test environment will have a serious impact on high-precision measurements. If a special gas refractive index correction device is used, the measurement accuracy can only reach micron or sub-micron level, and higher-precision measurement cannot be reached. (2) If there is a temperature change in vacuum chamber, the air pressure in chamber will also change drastically. The corresponding refractive index will also fluctuate severely, which will seriously affect the interferometer measurement. (3) During the vacuuming process, the internal and external pressure difference will cause micro deformation of vacuum chamber, and at the same time, it will also cause the optical window to be displaced and tilted, thereby changing the optical path of the measurement optical path. (4) In some test fields with variable temperature requirements, it is required that the measured object be heated as soon as possible and the temperature is homogeneous, which requires vacuum degree to be controlled at a certain level, such as about 100Pa, so as to keep the ability of convection and heat conduction. To sum up, in the precise measurement of micro-displacement and inclination of Michelson laser interferometer sensor, it is necessary to accurately control the degree of vacuum. This article will introduce the automatic control technology of vacuum degree and the specific implementation scheme. 2. Implementation plan During the test of Michelson laser interferometer sensor, vacuum degree is generally kept constant at about 100kPa and does not change with temperature. Because of this, vacuum degree control system as shown in Figure 2 is proposed to be implemented using an electronic flow control valve, and the specific conditions are as follows: (1) Use the capacitance vacuum gauge with a range of 1 Torr for vacuum measurement, and its accuracy can reach ±0.2%. (2) The high-precision PID vacuum pressure controller incorporating an electronic flow control valve with 24-bit A/D acquisition is used to match the measurement accuracy of high-precision vacuum pressure sensor and ensure the control accuracy. (3) Install a stepper motor proportional valve at air inlet of vacuum chamber to precisely adjust air intake flow. (4) During the control process, after vacuum pump turn on, it pumps at full speed and keeps the pumping speed unchanged. Then the PID parameters of controller are self-tuning, so that the controller can automatically adjust micro opening of KaoLu’s FC series electronic flow control valve to reach precise control of vacuum degree of the chamber. For further information, please visit https://www.genndih.com/proportional-flow-control-valve/mid-flow-proportional-valve-0-130L-min.html

Precision Control Technology of Pressure in Echelle Spectrometer and Its Implementation Precision Control Technology of Pressure in Echelle Spectrometer and Its Implementation Abstract: In order to reach the high-precision measurement of Echelle spectrometer, it is necessary to conduct precise and constant control of temperature and pressure for a long period in the whole process. This article will introduce the automatic pressure control technology for precise control of pressure in Echelle spectrometer using FC series high flow proportional valve, and introduce the specific implementation scheme in detail, especially the bi-directional control mode with better control effect. 1. Question As a full-spectrum direct-reading spectrometer, Echelle spectrometer is widely used in astronomy, geology, mining, chemical industry, metallurgy, medicine, environmental protection, agriculture, food hygiene, biochemistry, commodity inspection and national defense. Due to the serious influence of temperature and pressure, the Echelle spectrometer generally requires precise control of working temperature and pressure, especially the pressure control requires very high precision which using FC series high flow proportional valve (https://www.genndih.com/proportional-flow-control-valve.htm). If the control precision is not enough, it will bring the following effects: (1) The pressure fluctuation will change the refractive index of gas in Echelle spectrometer. (2) The pressure fluctuation will also cause the difference in pressure inside and outside the spectrometer to cause slight deformation of the optical path of spectrometer (especially at the optical window). At the same time, changes in temperature will also directly cause changes in air pressure. In conclusion, in order to reach the high-precision measurement of Echelle spectrometer, it is necessary to imply precise and constant control of temperature and pressure for a long period in the whole process. This article will introduce the automatic control technology of pressure for precise control of pressure in Echelle grating spectrometer using FC series high flow proportional valve, and introduce the specific implementation scheme in detail. 2. Implementation plan The structure of pressure control system of Echelle spectrometer is shown in the figure. In the specific implementation process, it is necessary to notice the following aspects according to the specific situation: (1) The working pressure of Echelle spectrometer is generally around an atmosphere pressure of 760torr, so it is necessary to select a pressure sensor that can meet the design requirements with measurement accuracy under this pressure. Choosing KaoLu’s high flow proportional valve is the best decision. For further information, please visit https://www.genndih.com/proportional-flow-control-valve/mid-flow-proportional-valve-0-130L-min.html (2) The automatic pressure control adopts a 24-bit high-precision PID controller. If the 24-bit measurement accuracy still cannot match the accuracy of pressure sensor, a higher-precision controller is required which is KaoLu’s high flow proportional valve. (3) The pressure control adopts bi-directional mode, that is, the air intake and exhaust flow are adjusted at the same time, but for pressure control near an atmosphere pressure, generally, air intake flow is fixed and exhaust flow is automatically adjusted to reach constant pressure control. (4) According to the working chamber size of Echelle spectrometer’s different sizes, different outlet flow control valves need to be selected. For large-sized space working laboratory, the outlet flow control can choose a high flow proportional valve with a larger outlet diameter; while for a small-sized space studio, the outlet flow control needs to choose a smaller and more precise high flow proportional valve. The same goes for the vacuum pump used for vacuum suction.

Precise Control of Vacuum in Cold and Hot Stage Abstract: Focusing on current problems of poor vacuum control accuracy and high price of supporting control system in the airtight vacuum cooling and heating stage, this article introduces the solution using domestic products, and introduces the details of upstream and downstream bi-directional control mode using KaoLu’s FC series electronic needle valve implementation process. This solution has been applied and verified, which can reach precise control of vacuum degree in a wide range, and the fluctuation of vacuum degree can be controlled within ±1%. The whole control system has high cost performance. 1. Question The airtight vacuum heating and cooling stage is a precision temperature-controlled heating and cooling stage that can be used in both vacuum and airtight environments. It has heating and cooling functions, and is suitable for applications such as microscopes and spectrometers to accurately heat or cool samples in a controlled vacuum environment. According to user requirements, for the current various airtight vacuum heating and cooling stage, in terms of vacuum degree control, the following problems need to be solved: (1) Whether it is international or domestic vacuum heating and cooling stage, the vacuum measurement and control also use Pirani vacuum gauge, so that the matching control system cannot achieve precise control of vacuum, such as the accuracy of research and simulation freeze-drying process cannot meet requirement. (2) The air-tight vacuum heating and cooling stage is generally small in size, and it has always been difficult to reach precise control within a wide range of vacuum degrees. The fluctuation of vacuum degree is large, and the fluctuation of vacuum degree in turn affects the temperature stability. (3) The international vacuum degree control system not only fails to meet the requirements of control accuracy, but also is expensive. Focusing on the above problems existing in the air-tight vacuum heating and cooling table, this article will introduce a solution with domestic products and high cost performance, and introduce the detailed implementation process. 2. Solution The overall structure of the vacuum degree precision control system of the airtight vacuum cooling and heating stage is shown in Figure 1. The whole system mainly includes a vacuum gauge, a numerical control needle valve, a PID controller and a vacuum pump. In order to improve the accuracy of vacuum measurement and control, a capacitive vacuum gauge with higher measurement accuracy (up to 0.2% of full scale) is used, which can cover the vacuum range of 0.01 to 760 Torr. If a higher vacuum environment is required, a Pirani vacuum gauge can also be used for measurement and control. In order to reach full-range vacuum control, two electronic needle valves are installed at the air inlet and outlet of hot and cold stage respectively. By adopting the upstream and downstream control modes respectively, precise control with a full-scale fluctuation rate of less than ±1% can be reached. The controller is the key to precise control. The high-precision PID controller of 24-bit A/D and 16-bit D/A is used in the scheme, and the independent dual-channel is convenient for upstream and downstream gas flow regulation and control. In conclusion, cost-effective precision control of KaoLu’s FC series electronic needle valve is possible with this proven vacuum control solution. For further information, please visit https://www.genndih.com/proportional-flow-control-valve/miniature-proportional-valve-0-32L-min.html

Upgrade of Pressure Control System of Low-Pressure Environment Simulation Cabin for Radiosonde Verification Abstract: Focusing on problem of poor control accuracy and stability of pressure control system of low-pressure environment simulation chamber used for radiosonde verification, and inaccurate configuration of pressure sensors and control systems. Users proposed upgrading and transformation requirements. This article introduces the implementation scheme of a new generation of low-pressure environment simulation chamber pressure control system, adopts a two-way control mode, and conducts a scheme verification test. The test results show that the control accuracy and stability are greatly improved. 1. Question One of the important methods of calibrating radiosonde is to test low-pressure environment simulation cabin on the ground. The structure of low-pressure environment simulation cabin in use is shown in Figure 1. There is a problem that the pressure control fluctuates greatly during the use of this low-pressure environment simulation chamber. The closer the pressure is to 1 atmosphere, the greater the fluctuation. The analysis believes that it is mainly caused by the following reasons: (1) The selection of pressure sensor is inaccurate. Proportion of the sensor error in the full-scale pressure range is not the same, which shows that the fluctuation is large when it is close to 1 atmosphere and the fluctuation is small when it is far away from 1 atmosphere. In real world, all problems exist. Large fluctuations, but the pressure sensor has the highest accuracy near 1 atmospheric pressure, and the pressure sensor error has completely covered the pressure fluctuation range at a distance away from 1 atmosphere pressure. In fact, there are large fluctuations as a whole, but the pressure sensor has the highest accuracy near 1 atmosphere pressure, and the error of pressure sensor has completely covered pressure fluctuation range at a distance away from 1 atmosphere pressure. (2) Pressure control adopts switch control mode. Vacuum pump and solenoid valve are opened or closed at the same time according to pressure setting value. Although gas storage tank is added as a buffer, it is difficult to achieve accurate and constant pressure in this semi-automatic control mode. (3) Controller does not use the PID automatic control method which is also the main reason for affecting pressure control accuracy. Based on the above analysis, focusing on the problems of poor control accuracy and stability of pressure control system with low-pressure environment simulation chamber used for calibration of the previous generation sound, and an inaccurate configuration of the pressure sensor and control system. Users proposed upgrading and transformation requirements. This article will introduce implementation scheme of the new generation with low-pressure environment simulation chamber pressure control system. Bi-directional control mode is proposed to be adopted, and the scheme verification test will be carried out, which proves that control accuracy and stability can be greatly improved. 2. Upgrading and reforming pressure control system using FC series electric needle valve The absolute pressure range of the low-pressure environment simulation chamber for sonde verification is 1torr~760torr.It is required that pressure of simulation chamber can be accurately and constant at any set point within this range, and it can even be controlled according to the set pressure transformation rate. For this reason, the specific upgrade scheme is to keep vacuum pump and vacuum solenoid valve on the basis of original pressure control system, replace pressure sensor and controller, remove energy storage tank, and increase numerically controlled air intake valve and exhaust valve. The specific scheme is as follows: (1) Capacitance pressure gauge with 10torr and 1000torrare used to cover measurement of the entire low pressure range, thereby ensuring measurement accuracy of the full range. (2) High-precision PID vacuum pressure controller is used to match measurement accuracy of capacitive pressure gauge and ensure control accuracy. (3) Install an electric needle valve at air inlet and exhaust port of vacuum chamber respectively. The electric needle valve is directly installed at air inlet. (4) The control mode adopts upstream mode and downstream mode respectively. Upstream mode is used to control air pressure below 10torr, and downstream mode is used to control air pressure in the range of 10~760torr using KaoLu electric needle valve (https://www.genndih.com/proportional-flow-control-valve.htm) (5) As shown in Figure 2, upstream mode is to maintain upstream pressure and outlet flow constant, and control chamber pressure by adjusting inlet flow. (6) As shown in Figure 3, downstream mode is to maintain upstream pressure and inlet flow constant, and control chamber pressure by adjusting exhaust flow. 3. Certification test of scheme For the above two control modes, two capacitive pressure gauges of 1torr and 1000torr, an electric needle valve and a 24-bit high-precision pressure controller were used to conduct the assessment test. The internal space of vacuum chamber used for test was 400×400× 500mm; the test device is shown in Figure 4 and Figure 5. During the upstream mode test, vacuum pump was first turned on and then pumped at full speed. Then the PID parameters of controller were self-tuned at about 68Pa. After the auto-tuning is completed, 8 set points of 12, 27, 40, 53, 67, 80, 93 and 107Pa are controlled respectively. The air pressure changes during the whole control process are shown in Figure 6. During the downstream mode test, vacuum pump was first turned on and then pumped at full speed, and air intake electric needle valve was adjusted to the position of micro intake. Then the PID parameters of controller were self-tuned at about 300torr. After the auto-tuning is completed, 5 set points of 70, 200, 300, 450 and 600 Torr are controlled respectively. The air pressure changes during the whole control process are shown in Figure 7. By expressing the above control effects at different low pressure constant points as fluctuation rate, fluctuation rate distribution in the entire range shown in Figures 8 and 9 is obtained. It can be seen from fluctuation rate distribution diagram that fluctuation rate can be accurately controlled within the range of ±1% in the whole range of low pressure. The large fluctuation at 12Pa is because the PID parameters obtained by self-tuning at 68Pa are invalid, and a separate PID parameter self-tuning is required. It can be seen from the above test results that the electric needle valve can improve the pressure control accuracy and stability by more than five times, and greatly improve the automation level and reliability of the low-pressure environment simulation chamber. For further information on the introduced electric needle valve, please visit https://www.genndih.com/proportional-flow-control-valve/miniature-proportional-valve-0-32L-min.html

Application of Electric Needle Valve and Dual-channel Controller in High Precision Pressure Control of Vacuum Freeze Drying Abstract: Capacitive pressure gauges have been widely used in vacuum freeze-drying process at present, which makes pressure controller and electric air intake regulating valve matched with capacitive pressure gauges. These two main links affecting the accuracy and repeatability of pressure control, particularly prominent. In order to solve the problem of control accuracy, this article introduces functions, technical indicators and applications of the latest domestic 2-channel 24-bit high-precision PID pressure controller and stepper motor-driven electric needle valve. It has been verified by experiments that the use of electric needle valve and high-precision controller in the upstream control mode can accurately control pressure within ±1%. This controller can also be used to monitor Pirani vacuum gauge during the freeze-drying process to automatically tune to the end point of initial freeze-drying process. 1. Questions Pressure control is an important process in vacuum freeze-drying process. Its control accuracy severely affects the product quality, especially for freeze-drying of some sensitive products. Therefore, in order to achieve a reliable freeze-drying process with high repeatability, the pressure must be accurately and repeatedly measured and controlled in drying room, which is one of the important indicators for examining the capability of freeze-drying hardware equipment. Due to pressure or vacuum degree during primary drying directly affects the temperature of the product sublimation interface at the same time, accurate and stable pressure control is very important for the primary drying process. However, in actual vacuum freeze-drying process, there are still the following problems in terms of accurate pressure control: (1) The problem of mismatch pressure controllers: Although the freeze-drying process and equipment are equipped with high-precision capacitive pressure gauges, the accuracy can reach 0.2% to 0.5% of the full scale, but at present, most localized supporting uses PLC for capacitive pressure measurement. For the measurement and control of DC voltage signal, the A/D and D/A conversion accuracy of PLC is obviously insufficient, which seriously affects the pressure measurement and control accuracy. A/D and D/A conversion accuracy must reach at least 16 bit to meet the needs of freeze-drying process. (2) The mismatch of air intake control valve: For vacuum pressure control in freeze-drying, constant pressure is basically in the order of a few Pa, so upstream air intake control mode is generally used. That is, when the pumping speeds of vacuum pump is constant, increasing air intake flow through electric regulating valve to reduce the pressure, and reduce air intake flow to increase the pressure. However, at present, solenoid valves with large hysteresis are still widely used in China for adjustment, which seriously affects the accuracy and repeatability of pressure control. At present, many low-hysteresis electric control valves driven by stepper motors have been used in the world. In order to solve the above problems of pressure control in freeze-drying process, this article will introduce functions, technical indicators and applications of the latest localized 2-channel 24-bit high-precision PID pressure controller and electric needle valve. After evaluation and verification of specific applications, the use of electric needle valve and high-precision PID pressure controller in upstream control mode can accurately control the pressure within ±1%. The 2-channel PID controller can also be used for both monitoring and recording of Pirani gauge during freeze-drying. 2. Localized 2-channel 24-bit high-precision PID pressure controller In order to take full advantage of measurement accuracy of capacitive pressure gauge, the data acquisition and control of controller requires at least 16-bit analog-to-digital and digital-to-analog converters. In recent years, KaoLu have developed the FC series of high-precision 24-bit general-purpose PID controllers, as shown in Figure 1. This series of PID controllers is far more powerful than foreign products, but the price is only one-eighth of foreign products. Its main performance indicators are as follows: (1) Precision: 24-bit A/D, 16-bit D/A. (2) Multi-channel: independent 1-channel or 2-channel. 2 channels can reach simultaneous measurement and control of dual sensors. (3) A variety of output parameters: 47 kinds of input signals (thermocouple, thermal resistance, DC voltage) can reach simultaneous testing, display and control of different parameters. (4) Multi-function: forward, reverse, forward and reverse two-way control. (5) PID program control: The improved PID algorithm supports PV differential and differential advance control. It can store 20 groups of PIDs and support 20 program curves (50 segments each). (6) Communication: Two-wire RS485, standard MODBUS RTU communication protocol. In the judgment of primary freeze-drying end point of freeze-drying, 2-channel controller in FC-20 series can be connected to a capacitive pressure gauge and a Pirani pressure gauge at the same time. The capacitive pressure gauge is used for vacuum pressure control, and the Pirani gauge is used for monitoring the change of water vapor during freeze-drying process, when the difference between two vacuum gauges disappears, the primary freeze-drying process is considered to be over. The typical change curve of the whole process is shown in Figure 2. 3. Localized stepper motor drives electric needle valve In order to reach high-precision adjustment of air intake valve, we have developed a series of electric needle valves with different flow rates based on needle valve using stepper motors. The magnetic hysteresis is much smaller than solenoid valve. As shown in Figure 3, the price is only one-third of foreign products, and the detailed technical indicators are shown in Figure 4. Inert gas and liquid​Stainless Steel​-1 ~ 7bar​ Model FC-20 FC-120 FC-300 FC-1000 Valve type Needle Valve Spool Drift Diameter 0.9mm 2.25mm 2.75mm 4.10mm Actuator Bipolar stepper motor control Response time 0.8sec(Open to close) Standard size G1/8” G3/8”  Fluid Inert gas and liquid  Contact Materials Stainless Steel  Pressure Range -1 ~ 7bar  -1 ~ 5bar   Maximum Flow   50L/min @7bar   240L/min @7bar   290L/min @7bar   600L/min @7bar   Linearity ±2% ±0.1 ~ 1% ±0.2 ~ 5% ±11% Repeatability (Full scale) ±0.1% Flow Resolution (Step length) 0.1L/min 0.1 ~ 0.2L/min 0.2 ~ 0.75L/min 1L/min Shift Resolution (Step length) 12.7um 25.4um Operating Temperature Range 0 ~ 84ºc Seal Standard FKM or other choices of seals Control Signal DC: 0 ~ 10V (or 4 ~ 20mA) Power Supply DC: 24V (12W) (Figure4 Technical indicators of KaoLu’s FC electric needle valve) 4. Assessment test of domestic PID controller and electronic needle valve In the assessment test, a capacitance pressure gauge with a range of 1 Torr was used, and the electronic needle valve was used as the intake valve to conduct the control test in the upstream mode. First turn on the vacuum pump and make it pump at full speed, and then self-tune the PID parameters of the PID controller at about 68Pa. After the self-tuning is completed, 8 set points of 12, 27, 40, 53, 67, 80, 93 and 107 Pa are controlled respectively. The change of vacuum degree during the whole control process is shown in Figure 5. The control effect of curve in Figure 5 is expressed in terms of fluctuation rate, and the fluctuation rate under different vacuum pressures as shown in Figure 6 is obtained. It can be seen from Figure 6 that the fluctuation rate is greater than 1% only when 12Pa control is in the entire pressure range. Obviously, it is not suitable to apply PID parameters obtained by self-tuning at 68Pa to 12Pa pressure control. It also required a separate PID parameter self-tuning. The introduced electronic needle valve is introduced in https://www.genndih.com/proportional-flow-control-valve.htm

Precise Control of Temperature and Pressure in Vacuum Concentration Process by New PID Controller and Fast Electric Needle Valve Abstract: In the process of vacuum concentration, concentration temperature and pressure are the core control parameters. This article focuses on a detailed approach to improve poor precision and large fluctuation of pressure control in current concentration instruments and equipment, and proposes a new dual-channel ultra-high-precision multi-function PID controller and high-speed electronic needle valve to reach target temperature in concentration process. 1. Question The working principle of vacuum concentration is to use vacuum and heating technology to vaporize solvent in a sample quickly and concentrate or a dry sample system under freeze-drying quickly, centrifugal concentration and rotary evaporation. Since different samples have different entropy value to temperature, and there is a strong correlation between pressure and temperature, the ability to accurately control the concentration temperature and pressure during vacuum concentration process has become the most concerned issue for users. In the current commonly used vacuum concentration equipment, following problems still exist: (1) The accuracy of pressure measurement and control is generally not high, especially in the case of low pressure, which is mainly due to insufficient accuracy of sensors that controllers used. The pressure control accuracy is not high and will have a serious impact on the temperature. (2) The downstream pressure control method is generally adopted in concentration instruments and equipment, that is, an electronic needle valve is installed between container and vacuum pump to control exhaust rate of the container in real time. This downstream method is suitable for accurate control of higher pressures, but it is difficult to achieve stable and accurate control for low pressures below 10mbar. (3) At present, the vast majority of electronic needle valves use electric actuators, and the time from closing to fully opening is basically more than 10 seconds. It is difficult to ensure control accuracy and stability of valve adjustment speed with such a serious hysteresis. (4) Due to the discharge of water and vapor two-phase medium in concentration process, the medium is often corrosive, which puts forward high requirements for corrosion resistance of downstream regulating valve. 2. Solution 2.1 Adopting high-precision pressure sensor For vacuum concentration process, pressure sensor is to ensure that entire concentration process is controllable. It is strongly recommended to use a high-precision pressure sensor to ensure the measurement of vacuum degree, quantity and control accuracy. The general vacuum control process basically adopts a mechanical vacuum pump, which at low pressure (absolute pressure) does not exceed 0.01mbar, whilst at high pressure it can reach closely to one atmospheric pressure, so it is recommended to use capacitive film gauges for high-precision pressure sensors, as shown in Figure 1. The absolute measurement accuracy can reach ±0.2%. If the pressure range used by the concentration instrument and equipment is relatively wide, it is recommended to use two sensors with different ranges to cover, such as 10 Torr and 1000 Torr. If other types of vacuum sensors are used, it should require a certain precision degree. 2.2 Adopting high-precision dual-channel PID controller In vacuum pressure measurement and control, in order to make full use of measurement accuracy of above-mentioned diaphragm pressure gauge, it requires at least 16-bit analog-to-digital and digital-to-analog converters for data acquisition and control of controller. At present, the commonality PID controller with measurement and control accuracy of 24 bits has been launched, as shown in Figure 2. For the process control of vacuum concentration, this series of PID controllers has the following characteristics: (1) High precision: 24-bit A/D acquisition, 16-bit D/A output. (2) Multi-channel: independent 1-channel and 2-channel. 2-channel can reach simultaneous measurement and control of temperature and pressure. (3) Multi-function: 47 kinds of input signals (thermocouple, thermal resistance, DC voltage) can reach simultaneous testing, display and control of different parameters. Also can perform forward and reverse control (two-way control mode). (4) PID control: The improved PID algorithm can support PV differential and differential advance control. There are 20 groups of group PIDs. (5) Dual sensor switching: Each channel can support dual sensor switching of high and low temperature and high and low vacuum. Two channels can form a control combination with a total of four sensors connected. (6) Program control: Up to 20 kinds of concentration programs can be established and stored by themselves. When concentrating, just select and call to start (program control mode). 2.3 Increasing upstream air intake control and two-way control mode The currently common downstream control mode is more suitable for concentration process where pressure is close to atmospheric pressure, but for the low pressure concentration process below 10mbar, it is necessary to introduce the upstream air intake control mode, that is, increase intake channel on concentration container, and control air intake through the electronic needle valve. The air intake flow of air passage can be used to achieve accurate control of pressure. As shown in Figure 3, local-made electronic needle valves with various flow rates are currently available. Combined with downstream vacuum pump, accurate control of high vacuum (low pressure) can be reached through upstream mode. In order to satisfy the accurate control of low and high pressure full scale at the same time, the dual sensor and two-way control mode as shown in Figure 4 can be used. In the control mode shown in Figure 4, it is necessary to use the forward and reverse control and dual-sensor automatic switching functions of above-mentioned VPC-2021 series dual-channel controller, that is, during different air pressure control processes, the controller automatically switches corresponding range of vacuum gauge, and select the corresponding electronic needle valve and high-speed electric ball valve for control. 2.4 Adopting high-speed electronic needle valve The so-called high-speed valve generally means that action time of electronic needle valve from fully closed to opened is less than 1s, which is very important for gas flow and pressure control. Especially for vacuum concentration process, the fast response of air pressure control can ensure the accuracy, safety and increase the evaporation rate of concentration. At present, localized high-speed electronic needle valves have been developed, as shown in Figure 5. FC series miniaturized high-speed is upgraded products of currently commonly used electric butterfly valve. Combined with VPC2021 series temperature/pressure controller, it can form a fast and accurate vacuum pressure closed-loop control system. Please visit https://www.genndih.com/proportional-flow-control-valve.htm 2.5 Adopting vacuum control regulator In the current vacuum concentration instruments and equipment, concentration occurs in a hermetic container. The vacuum pump is used to extract air from hermetic container, and air pressure in hermetic container can be kept constant at set value by adjusting air flow rate. This is a typical flow control type constant pressure mode. This flow-controlled pressure regulation method is equivalent to an open-loop control method. There is a self-generated gas inside container, and self-generated gas has no obvious regularity (such as change of linearity), which is harmful to the accurate control of internal pressure of container. For this type of flow-controlled pressure regulation, as shown in Figure 2, an air intake channel is added at the front end of concentration container, and air intake air flow is adjusted to control internal vacuum of container to a stable set value. For some vacuum concentration instruments and equipment, it is not allowed to add additional air inlet channels, and the pressure-controlled regulator shown in Figure 6 can be used here. An electronic vacuum regulator is actually an integrated unit with a built-in vacuum pressure sensor, microcontroller, chamber and two electronic needle valves. In vacuum pressure control process, the built-in sensor measures pressure in chamber. If pressure is less than set value, the valve at air intake port will be opened until it is equal to set value. If pressure is greater than set value, the valve at exhaust port will be opened until it is equal to set value. It should ensure that pressure in chamber is always maintained at set value, and regulator cavity is communicated with concentrating container, that is, regulator cavity pressure is always equal to the concentrating container pressure. It can be seen that pressure-controlled regulator is an independent vacuum pressure regulator with its own air intake valve. As shown in Figure 6, pressure-controlled pressure regulator can also be connected to an external sensor, and set value can be set manually or through a PID controller. For more reference about electronic vacuum regulator, please visit https://www.genndih.com/proportional-pressure-regulator/Electronic-Vacuum-Regulator-1-0bar.html

Abstract: This article mainly introduces the work in localized substitution. The substitute product is Emerson TESCOM ER5000 series electronic pressure regulator and its back pressure valve. Also introduce the features and deficiencies of KaoLu’s electric actuated needle valve, putting forward the technical route, describing performance indicators, and introducing the functional expansion and technological innovation. We can see that localized substitute products have more advantages, low cost high performance and flexibility of use. 1. Emerson ER5000 series electronic pressure regulator 1.1. Structure and principle of electronic pressure regulator Emerson’s latest TESCOM ER5000 series electronic pressure regulator is a multifunctional integrated electronic pressure regulator that integrates three components: pressure sensor, PID (proportional-integral-derivative) controller and electric actuated needle valve. It is integrated with electric actuated needle valve to form a complete control mechanism. TESCOM ER5000 electronic pressure regulator and its basic structure are shown in Figure 1-1. From Figure 1-1, we can see that function of ER5000 electronic pressure regulator is to control pressure at bottom outlet, reducing intake pressure and control it to the set pressure, so that the pressure at the bottom outlet is always consistent with the set pressure. ER5000 electronic pressure regulator is actually an electronic pressure reducing valve, its working principle is shown in Figure 1-2. External air source supplies pressure to ER5000, and supply pressure becomes the output pressure at outlet through opened intake valve, and this output pressure feeds back to the PID controller through the pressure sensor. If the feedback value is lower than pressure set value, the controller continues to control intake valve to open it until feedback value equals set value. When the above two values are equal, the intake valve will close, and the outlet will continue to output a constant set point pressure. If feedback value is higher than set value, the controller will actuate an exhaust valve, thereby exhausting the excess outlet pressure until feedback signal equals the set value. When the above two values are equal, the exhaust valve will close, and outlet will also continue to output a constant set point pressure. Figure1-2 TESCOM ER500 electronic pressure regulator schematic diagram 1.2. Typical applications ER5000 pressure controller mainly has two applied directions, one is single machine application, and the other is application work with other special valves to achieve pressure regulation and control in different ranges. (1) Single machine application: It can be seen from above structure and principle that TESCOM ER5000 electronic pressure controller is a very typical electronic pressure reducing valve. In the case of single machine use, the controller itself can reduce pressure and accurately control the gas source with pressure below 8.2bar, and even control the wide vacuum. In addition, in single machine application, it can respectively use two control modes, internal and external feedback. It shows in Figure 1-3 and Figure 1-4. (2) Use in conjunction: An important application of ER5000 electronic pressure regulator is to use it as a pilot valve in conjunction with other regulating valves to regulate a wider pressure range. Greater pressure relief applications are shown in Figure 1-5, and are used in conjunction with a back pressure valve in Figure 1-6. 1.3. Performance indicators Since TESCOM ER5000 series electronic pressure regulator is an integration of three parts: pressure sensor, PID controller and two-way pressure regulating valve, the technical indicators of each part represent the overall performance of the controller, and the relevant technical indicators and functions are listed as follows: (1) Pressure control principle: double solenoid valve three-way pressure control. (2) Medium type: clean, dry inert gas or instrument-grade air. (3) Air intake pressure (absolute pressure): minimum (vacuum pump pressure), maximum 8.2bar (820kPa) (4) Air outlet pressure (absolute pressure): minimum 0.07bar (7kPa), maximum 8.2bar (820kPa) (5) Input signal: USB, RS485, 4~20mA, 1~5V or 0~10V. (6) External sensor feedback signal: 4~20mA, 1~5V or 0~10V. (7) Measurement accuracy of internal pressure sensor: ±0.10% (FSO), including ±0.05% (FSO) linearity and ±0.05% (FSO) hysteresis. (8) Controller A/D conversion: 16 bits. (9) Controller repeatability: ±0.05% (FSO). (10) Controller resolution sensitivity: ±0.03% (FSO). (11) Control mode: PID (combined with the special software ERTune for PID parameter debugging and optimization). (12) Control mode: internal feedback, external feedback and double loop. We will focus on three control modes of ER5000 electronic pressure regulator which is a technical highlight of it: (1) Internal feedback mode: This mode only uses internal sensors. The internal feedback mode uses ER5000 internal pressure sensor to monitor absolute pressure inside the controller in range of 1~100psig/0.07~6.9bar. (2) External feedback mode: This mode only uses external sensors. External Feedback mode utilizes a user-supplied external sensor to monitor system pressure, which is installed in pipe line and provides direct feedback to ER5000. (3) Dual loop mode: This mode uses both internal and external sensors in a “loop-in-loop” layout. Dual loop mode executes one PID loop within another PID loop. The inner circuit uses controller’s internal sensor, and the outer circuit uses external sensor. 1.4. Functions and Features From the above introduction, the following functions and features of the ER5000 electronic pressure regulator can be summarized: (1) The main function of ER5000 electronic pressure regulator is to control gas pressure (not flow), which can reach accurate control of pressure in sealed containers and pipelines. (2) The overall integrated structure integrates pressure sensor, PID controller and two-way pressure regulating valve, making the overall structure small and easy to install and use in parallel with multiple units. (3) As a typical electronic pressure regulator, it can directly reduce the air source pressure with a maximum of 8.2bar and control it accurately and constant pressure (air intake is positive pressure), and can also be used to control low pressure (wide vacuum, air intake is vacuum), and minimum pressure can reach 0.07bar (7kPa). (4) The ER5000 electronic pressure regulator can be used as a pilot valve to drive various large-scale pressure reducing valves and back pressure valves. The outlet of controller is connected to pilot ports of other back pressure valves to realize pressure regulation and control in a larger range. (5) The measurement accuracy of pressure sensor is ±0.1% and the 16-bit A/D conversion is a medium and high-end technical index, which can meet most applications. (6) The digital PID control mode can reach fast speed and accurate control of pressure. (7) Three control modes of internal feedback, external feedback and dual loop make ER5000 electronic pressure regulator have greater flexibility in use, and the best control mode can be selected according to actual use requirements. 1.5. Insufficiency of pressure controller Although ER5000 electronic pressure regulator has many function and features mentioned above, it still has the following limitations and deficiencies in practical applications. (1) The ER5000 electronic pressure regulator integrates three most common components in the field of vacuum pressure control; due to it is an integrated structure rather than a modular design structure. This limits application of ER5000 electronic pressure regulator. For example, ER5000 electronic pressure regulator integrates two solenoid valves, but it can only control gas pressure, but can’t control gas flow that only requires a single solenoid valve. (2) The ER5000 electronic pressure regulator focuses more on positive pressure control, and can also work partial negative pressure control. This is mainly due to the high leak rate of valve used, so sensor (especially external sensor) and PID are not used power of control. If gas leakage rate of valve inside the controller can be reduced, the controller can completely cover the control of entire vacuum degree range, extending the current vacuum degree of 7kPa to about 1Pa. (3) In application of driving various large-range pressure reducing valves and back pressure valves, the use of higher-priced ER5000 electronic pressure regulator as pilot valve has a very low cost performance, and electric actuated needle valve can be used. (4) The 16-bit A/D conversion of ER5000 electronic pressure regulator is a medium and high-end technical index. If an external high-precision pressure sensor is used, a 24-bit A/D converter is required, which makes ER5000 electronic pressure regulator unable to meet some requirements in occasions that require high measurement and control accuracy. (5) The on-site operation is very complicated. Although ER5000 electronic pressure regulator adopts PID control method, the adjustment of PID parameters requires the use of special software. The controller itself lacks PID parameter self-tuning function, and needs to be connected to a computer. (6) The ER5000 electronic pressure regulator itself lacks the display function, and it needs to connect to the computer and use the supporting software to debug and display the control process and results. (7) The overall price of ER5000 electronic pressure regulator is high, and the operation is complicated, which has higher requirements for operators. Combined with above-mentioned deficiencies of controller, this makes ER5000 electronic pressure regulator not cost-effective, and it is obviously very extravagant and wasteful to use in many occasions. 2. Localized alternative technology route For localized replacement of Emerson’s latest generation TESCOM ER5000 series electronic pressure regulator, the technical route is to first realize the measurement and control function of ER5000 electronic pressure regulator, and provide a cost-effective domestic electronic pressure regulator. Then, the module structure technology route is adopted to separate the vacuum pressure sensor, PID controller and electronic valve into their own independent modules. Each type of module is composed of a series of components with different technical indicators. Through the combination of these modules with different performance indicators, different control functions and precision requirements can be realized, and the controller functions can be expanded to meet different needs and have low cost high performance. 2.1. To reach the function of ER5000 electronic pressure regulator (1) Localized substitute products must achieve most functions of ER5000 electronic pressure controller, that is, to realize reducing pressure and pressure control functions of ER5000 electronic pressure regulator itself. (2) Localized substitute products, like ER5000 pressure controller, can act as a pilot valve to reduce pressure and control gas with a large range and high pressure range. (3) Localized substitute products have the function of setting value input and display, and do not need software and connection to a computer for operation. (4) The price of localized substitute products is low and cost-effective. 2.2. Modular structure and function expansion (1) Modular structure is divided into three modules: sensor, PID controller and electronic valve. (2) PID controller module is the core device of all modules which determines the measurement and control accuracy, the types of sensors and electronic valves that can be used together, the control method and control mode. PID controller module will use a 24-bit A/D converter to improve measurement and control accuracy, integrate two independent control channels. It can control 2 vacuum pressures or 1 vacuum pressure and 1 temperature at the same time. Also, it can connect a variety of vacuum pressure and temperature sensors. The combination of 2 channels can perform forward and reverse bidirectional control to meet the upstream and downstream control modes of vacuum pressure. It can have dual sensor automatic switching function to cover a wide range of measurement and control. The PID controller with program setting function can input multiple control process curves. Multiple groups of PID parameters can be input and stored, the PID parameter adjustment has self-tuning function, and the controller has a color LCD screen to display the entire process parameters and results. 3. Localized alternative products According to above-mentioned localization alternative technical route, KaoLu has developed corresponding products, electric actuated needle valve. 3.1. Digital pressure regulator The locally produced digital display pressure regulator includes positive pressure type and vacuum type. The pressure control principle and basic structure are the same as those of Emerson TESCOM ER5000 series electronic pressure regulator, as shown in Figure 3-1. Please visit https://www.genndih.com/proportional-pressure-regulator.htm The local electronic pressure regulator is also an integrated structure of three parts: a pressure sensor, a controller and a two-way pressure regulating valve. The relevant technical indicators and functions are listed as follows: (1) Pressure control principle: double solenoid valve three-way pressure control. (2) Medium type: clean, dry inert gas or instrument-grade air. (3) Air intake pressure (absolute pressure): minimum (vacuum pump pressure), maximum 50bar (5MPa) (4) Air outlet pressure (absolute pressure): minimum 0.21bar (21kPa), maximum 30bar (3M Pa) (5) Input signal: 4~20mA, 0~5V or 0~10V. (6) External sensor feedback signal: 4~20mA, 0~5V or 0~10V. (7) Measurement accuracy of internal pressure sensor: ±1.0% (FSO), including ±0.5% (FSO) linearity and ±0.5% (FSO) hysteresis. (8) Controller A/D conversion: 12 bits. (9) Controller repeatability: ±0.5% (FSO). (10) Controller resolution sensitivity: ±0.2% (FSO). (11) Control method: Built-in PID automatic control, without manual intervention. (12) Control mode: internal feedback and external feedback. It can be seen that some technical indicators of localized pressure controller have been reduced, such as 12-bit A/D conversion and ±1.0% measurement accuracy, but the use of pressure range has been expanded, also display and input functions have been added. The pressure controller can be used independently without external computer and software debugging which reduces the difficulty of operation, improves low cost high performance, and can basically meet the application in most fields. 3.2. Back pressure valve (high pressure type and vacuum type) The locally produced new back pressure valve modules are separately divided into high pressure type and vacuum type back pressure valves. Both back pressure valves use the above digital display pressure controller as a pilot valve for control, but the new back pressure valve is not suitable for traditional back pressure valves such as Emerson TESCOM. Significant improvement has been made to the pressure valve. The traditional back pressure valve has a valve seat fixed on the valve body, and valve seat is tightly fitted with valve core to achieve sealing effect. It provides basic pressure control for most simple processes. In this design, a spring or other means provides a preset loading force that seals valve plug against valve seat. When the force of pipeline pressure acting on spool is the same as loading force, the back pressure valve works normally under preset pressure state; when pressure at the inlet end of valve increases, the force acting on spool exceeds At the preset loading force, valve core and valve seat are separated, releasing excess pressure at inlet end until preset pressure is restored. In the traditional back pressure valve structure, when instantaneous flow rate changes greatly or inlet pressure fluctuates frequently, the control pressure accuracy is low. Reasons are as follows: (1) Since most traditional back pressure valves with a control pressure exceeding 20bar use a piston as load mechanism for spool. O-ring in piston increases friction which makes the spool act stuck. (2) The inlet and outlet flow passages of traditional back pressure valves are mostly single passages with a fixed cross-sectional area. When flow rate at inlet of valve increases or decreases rapidly, the CV value (flow capacity) of valve does not change, it will make the inlet pressure fluctuates violently. (3) The valve core and valve seat of traditional back pressure valve, due to the need for sealing, there is stress or friction when fitting and frequent opening and closing. This will cause them to wear and consume each other, destroy the initial shape, and change CV value unpredictably. The new type of back pressure valve is a bonnet and valve body structure connected from top to bottom, as shown in Figure 3-2. A diaphragm is connected between valve cover and valve body. A pilot air hole is provided on the top of valve cover. The pilot air hole is connected to movable groove opened at the bottom of valve cover for undulating movement of the middle of diaphragm through the air source channel opened inside the valve cover, forming an up and down connection. On the side wall of valve body, there are respectively oppositely arranged medium inlet and medium outlet, medium inlet is connected with a plurality of inlet holes opened on the upper surface of valve body, and the medium outlet is connected with a plurality of outlet holes opened on the upper surface of valve body. The outstanding features of new back pressure valve are that the entire action is frictionless. Also, it does not produce pressure lag, has high inlet pressure stability and greater flow capacity. 3.3. Two-way high-precision PID controller For PID control module, in order to meet a wide range of vacuum pressure control requirements, KaoLu has produced VPC2021 series PID controllers, which can measure, display and control vacuum, pressure and temperature. Using 24-bit data acquisition and artificial intelligence PID control technology, it can be connected to various types of vacuum, pressure and temperature sensors, and can control various types of electric needle valves, electric valves and heaters and other executive structures. It can also achieve high-precision vacuum. The fixed-point and program control of parameters such as pressure and temperature is a high-performance and cost-effective controller that replaces foreign high-end controller products. As shown in Figure 3-3, VPC2021 series PID controller has two-way independent measurement and control function which can measure, display and control parameters on different channels at the same time. If two channels are connected to sensors of the same type but different ranges, as shown in Figure 3-4, automatic switching between two sensors can be reached according to test value, thus covering a wide range of measurement and control. The main technical indicators of VPC2021 series dual-channel high-precision PID controller are as follows: (1) Measurement accuracy: ±0.05%FS (24-bit A/D). (2) Input signal: Can be connected to many vacuum pressure sensors, 32 signal input types (voltage, current, thermocouple, thermal resistance). (3) Control output: 4 types of control output (analog signal, solid state relay, relay, SCR), which can be connected to many electric regulating valves. (4) Control algorithm: PID control and self-tuning (20 groups of PID parameters can be stored and recalled). (5) Control mode: fixed-point and program control, can support up to 9 control curves, each of which can be set with 24 program curves. (6) Channel: dual channel, dual channel sensor switches automatically. (7) Communication mode: RS 485 and Ethernet communication. (8) Power supply: AC (86-260V) or DC 24V. (9) Dimensions: 96×96×136.5mm (cut size 92×92mm) 3.4. High-speed electric flow control valve For electronic valve module, in order to meet the high-speed regulation of different sizes of flow, KaoLu has launched two series of electronic valves, one series is electric needle valve for small flow control, and the other series is electric ball valve and butterfly valve for large flow control. The biggest feature of these two series of electronic valves is that they can be electronically controlled, and have a high-speed closing time within 1s, which is a very rare fast electronic valve in Taiwan. As shown in Figure 3-5, the Electric Needle Valve FC Series combines the precision and repeatability advantages of a stepper motor with the linearity and resolution of a needle valve, resulting in less than 2% hysteresis, 2% linearity, and an adjustable flow control with 1% repeatability and 0.2% resolution is an upgraded product of the commonly used electromagnetic proportional valve. Combined with KaoLu’s QKL-B3V electronic vacuum pressure controller, it can form a fast and accurate vacuum pressure closed-loop control system. Please visit https://www.genndih.com/proportional-flow-control-valve.htm The main technical indicators and characteristics of FC series electric needle valve are as follows: (1) Multi-specification throttling area: from low-flow diameter 0.9mm (0~50L/min gas) to high-flow diameter 4.10mm (0 to 660 L/min gas) needle valve throttling area, It can meet different application needs. (2) High linearity: The linearity of less than 2% simplifies the look-up table or the matching of external control hardware and software, and simplifies the relationship between command input and flow output. (3) High repeatability: By reaching the same flow rate of 0.1% each time, the FC series electric needle valve can provide long-term stable consistency. (4) Wide pressure range: With a vacuum of 5 or 7 bar, depending on the size of hole, the inlet environment can cover a wide pressure range. The stiffness and power of motor ensures that valve opens with the same input command, independent of pressure. (5) Low Hysteresis: Hysteresis of less than 2% makes integration and programming simple, providing consistent flow when increasing and decreasing to the set point. (6) High resolution: 0.2% resolution allows FC series electric needle valve to perform minimal flow adjustment according to small changes in adjustment command, providing excellent controllability. (7) Quick response: the whole travel time is less than 1 second, which can provide timely and fast flow regulation and control. (8) Working voltage: VDC 24V. (9) Input signal: 4~20mA, 0~5V and 0~10V. As shown in Figure 3-6, NCBV series electric ball valve is composed of high-speed electric actuator and high-quality V-shaped ball valve, which is an upgraded product of current common used slow-speed electric ball valve. Combined with KaoLu’s QKL-B3V series electronic vacuum pressure regulator, it can form a fast and accurate vacuum pressure closed-loop control system. 4. Conclusion To sum up, through the development of a series of localized alternative products, it can basically completely replace Emerson’s latest generation TESCOM ER5000 series electronic pressure controller and its back pressure valve, and low cost high performance is greatly improved. Importantly, on the basis of localized substitution, a more flexible and easy-to-use modular structure has been designed, the function expansion and technological innovation of individual modular products have been carried out, and a new type of back pressure valve and high-speed electric flow control valve have been developed. The PID controller has more powerful functions and measurement accuracy, and the whole series of localized alternative products have higher low cost high performance.

A Precise Control Method of Temperature and Pressure in Rayleigh-Brillouin Scattering Spectrometry Abstract: For the Rayleigh-Brillouin scattering (RBS) spectroscopy experimental device, users proposed to reach high-precision control of temperature and pressure of measuring gas chamber. This article introduces a specific implementation, in which high-precision temperature control is implemented using semiconductor TEC modules and proportional control flow valve. Pressure control adopts a high-precision vacuum pressure control system, which includes a high-precision pressure sensor, a precision proportional control flow valve and a 24-bit acquisition precision PID controller. This temperature and pressure control scheme has been widely used and proven. The introduced proportional flow control valve is introduced in https://www.genndih.com/proportional-flow-control-valve.htm 1. Technique requirement According to customer requirements, temperature and pressure in Rayleigh-Brillouin scattering (RBS) spectroscopy as shown in Figure 1(the content of the red box area) for precise control, the specific requirements are as follows: (1) Temperature range is 300K~318K; temperature control accuracy is ±0.02K. (2) Pressure range is 30kPa~90kPa (absolute pressure); pressure control accuracy is ±0.1kPa; atmosphere is 99.9trogen. 2. Temperature control scheme For high-precision temperature control near room temperature, it is proposed to use semiconductor heating and cooling technology shown in Figure 2 to reach, the specific contents include: (1) Heating refrigerator: TEC module. (2) Sensor: platinum resistance or thermistor temperature. (3) PID controller: high-precision 24-bit temperature and pressure controller. 3. Pressure control scheme The absolute pressure range required for experimental device to work is 30kPa~ 90kPa, and pressure within this range is required to be accurate and constant at any set point. Using KaoLu’s proportional control flow valve is the best choice. Because of it, vacuum pressure control system as shown in Figure 2 is proposed to be implemented, and details are as follows: (1) Using a capacitance pressure gauge with a range of 1000torr for pressure measurement, its accuracy can reach ±0.2%. A vacuum pressure sensor with a higher accuracy of ±0.05% can also be used for measurement. (2) The high-precision PID vacuum pressure controller with 24-bit A/D acquisition is used to match the measurement accuracy of high-precision vacuum pressure sensor and ensure control accuracy. (3) Install a proportional flow control valve at air inlet and exhaust port of air chamber respectively. The proportional flow control valve is directly installed at air inlet. https://www.genndih.com/proportional-flow-control-valve/mid-flow-proportional-valve-0-130L-min.html (4) During the control process, the pumping speed is guaranteed to be constant after vacuum pump is turned on. First, you need to set the air intake electronic needle valve so that pressure and flow of intake port are constant, and then perform self-tuning of PID parameters. Last, realize precise control of air chamber pressure by automatically adjusting the flow rate of exhaust port.

Accurate Control Method of Low Pressure in Plume Characteristics Test of NanoSat Electrothermal Plasma Microthruster Abstract: This article focuses on various nanosat electrothermal Plasma microthrusters. Taking the pocket rocket as an example, which works in the low pressure range of 0.1 to 10torr, the characteristics of different working gases and different low pressures on the plume are analyzed. The resulting effects illustrate the importance of precise control of low pressure. Regarding the technical problem of precise control of low air pressure of the propeller, this paper introduces the specific implementation method in detail, and conducts an assessment test. The test results show that the fluctuation degree of low air pressure control can reach within ±1%. In the end, this paper optimizes the test method, and proposes a more practical technical scheme for full-scale low pressure precise control. 1. Question In recent years, with the rapid development of NanoSat, there is an urgent need for small-volume, light-weight, low-cost and high-efficiency micro-thrusters. Therefore, it is necessary to carry out the test and evaluation of physical properties such as the characteristics of thruster’s plasma plume. The characteristics of plasma plume are significantly affected by the working gas and environment pressure. Taking the performance test of foreign pocket rocket plume as an example, the necessity and importance of precise control of low pressure are analyzed. As a typical representative of NanoSat applications, Pocket Rocket is an electrothermal radio-frequency plasma thruster that can achieve thrust in the order of μN to mN. Because of its compact size and the use of capacitive radio frequency discharge, pocket rockets can obtain high-density plasma jets under low power conditions. It’s light-weight, low-cost, low-thrust, and large in specific impulse, also can work in the form of arrays, which are especially suitable for microarrays and provide power for the long term. As shown in Figure 1, the horizontal vacuum chamber provides a low pressure environment for testing the characteristics of pocket rocket plasma plume. The vacuum chamber is a multi-functional low-pressure environment simulation test chamber, which can integrate a variety of test equipment for the performance test and evaluation of various plasma thrusters. As shown in Figure 2, in order to form a low-pressure environment, the vacuum chamber is equipped with molecular pump, mechanical pump, ionization vacuum gauge and capacitance pressure gauge. Vacuum chamber can reach a reference vacuum of 0.93mPa. The gas working fluids in the test are usually nitrogen and argon. Under the condition of RF power and frequency of 20W and 13.56MHz respectively, the plume characteristics of pocket rocket were tested under different low pressures. Figure 3 is an experimental photo of plasma plume injected to different working gases at different pressures. Figure a is about 1.5torr low pressure argon, Figure b is about 4.0torr high pressure argon, Figure c is about 1.0torr low pressure nitrogen, and Figure d is about 7.0torr high pressure nitrogen. It can be seen from the figure that both nitrogen and argon plumes spread at a certain cone angle at high pressure. Beams are collimated at the low pressure, but the effect of these features on thrust generation is not clear and requires further study. To sum up, different working gases and different low pressures will have a significant impact on plume characteristics. Micro-thruster of pocket rocket works in the low pressure range of 0.1 to 10torr. Testing and evaluating plume characteristics within this range requires precise control of low pressure. This article will introduce the specific implementation method in detail for low pressure control, test and evaluate the implementation method. Finally, the implementation method will be optimized, and the accurate control technical scheme of low pressure full range is proposed. 2. The precise control method and test assessment of low pressure The so-called low pressure generally refers to the absolute pressure lower than 1 standard atmospheric pressure and the range is 0.1~760torr. Capacitance pressure gauge is commonly used to accurately measure low atmosphere pressure. It usually adopted two different ranges of 10torr and 1000torr of capacitance pressure gauge to cover the measurement of entire low pressure range. The vacuum chamber of simulation test device usually needs to be controlled by low pressure through intake and exhaust. According to the airflow direction, air intake end is generally defined as the upstream, and exhaust end of vacuum pump is defined as the downstream. According to the control accuracy, two control modes of upstream and downstream are generally used to achieve accurate control of low air pressure with different ranges (10torr and 1000torr). As shown in Figure 4, the upstream mode is to maintain the upstream pressure and outlet flow, and control chamber pressure by adjusting inlet flow. As shown in Figure 5, the downstream mode is to maintain the upstream pressure and inlet flow, and control chamber pressure by adjusting exhaust flow. For the above two control modes, two capacitive pressure gauges of 1torr and 1000torr and a 24-bit high-precision pressure controller were used to conduct the assessment test. The test device is shown in Figure 6 and Figure 7. During the upstream mode test process, the vacuum pump was first turned on and then pumped at full speed, and PID parameters of controller were self-tuned at about 68Pa. After the self-tuning is completed, 8 set points of 12, 27, 40, 53, 67, 80, 93 and 107Pa are controlled respectively. Air pressure change during the whole control process is shown in Figure 8. During the downstream mode test process, the vacuum pump was firstly turned on and then pumped at full speed, and air intake valve was adjusted to the position of micro intake, and then PID parameters of controller were self-tuned at about 300torr. After the auto-tuning is completed, 5 set points of 70, 200, 300, 450 and 600 Torr are controlled respectively. Air pressure change during the whole control process is shown in Figure 9. By expressing the above control effects at different low pressure constant points as fluctuation rate, the fluctuation rate distribution in the entire range shown in Figure 10 and Figure 11 is obtained. It can be seen from fluctuation rate distribution diagram that fluctuation rate can be accurately controlled within the range of ±1% in the whole range of low pressure, and the large fluctuation at 12Pa is due to PID parameters obtained by self-tuning at 68Pa. It is unreasonable, and a separate PID parameter self-tuning is required. 3. Full-scale low pressure precise control implementation It can be seen from the above air pressure precise control methods that different control modes can be selected according to actual needs. For example, the upstream mode can be selected for low air pressure control below 10torr, and the downstream mode can be selected for high air pressure control in the range of 10 to 1000torr. In most low-pressure environment simulation test equipment, especially for the performance test of thrusters, it is necessary to reach precise control of air pressure and automation in the entire low-pressure range, so it is not the best choice to use or switch the upstream and downstream control modes alone. In order to reach automatic and precise control in the full range of low pressure, we integrated the upstream and downstream modes, and proposed a technical scheme for two-way control mode. The overall scheme layout is shown in Figure 12. In the full-scale control process of low-pressure, two capacitive vacuum gauges with different measurement ranges are required to cover the full-scale range. A continuous capacitive vacuum gauge and a continuous ionization vacuum gauge can also be used to cover a wider low-pressure range. For further information about our electronic needle valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm In the technical scheme of two-way control mode, higher requirements are put forward for controller and electronic needle valve, which are mainly reflected in the following aspects: (1) It is required to have the ability to connect two vacuum sensors at the same time, and to switch between two vacuum sensors according to low pressure measurement value, so as to accurately measure and control the low pressure in time. (2) The controller needs to have high measurement accuracy, such as 24-bit A/D sampling accuracy, to meet measurement accuracy requirements of different vacuum gauges and give full play to measurement capability of vacuum gauge. (3) In two-way control mode, vacuum pressure controller is also required to have forward and reverse control functions, that is, reverse control for the upstream electronic needle valve and reverse control for the downstream electronic ball valve. (4) In two-way control mode, electronic needle valve and electronic ball valve are responsible for the adjustment of upstream and downstream gas flow need to work alternately, so these electronic needle valves need to have the fastest possible response speed. The smaller the vacuum chamber, the smaller the air pressure inertia, the faster the response speed is required, the general requirement is that the time from fully closed to fully open of valve is within 2 seconds or even lower. To sum up, by adopting low pressure control scheme of the above two-way mode, especially after adopting the new high-performance vacuum pressure controller and high-speed electronic needle valve, the precise control of low pressure full range can be reached.

Abstract: The hydrogen supply system is an important part of fuel cell system, and dynamic control of pressure difference between air side and hydrogen side is particularly important for the reliability of entire fuel cell system. This article will focus on problems exist in hydrogen pressure control of hydrogen fuel cell system, also recommend the use of a precision proportional flow control valve, and introduce characteristics and technical parameters of proportional flow control valve in detail. 1. The formulation of question As an important part of fuel cell system, hydrogen supply system collaborate with voltaic pile, air supply system, water and heat management system and electronic power system to ensure the stable supply of hydrogen flow and pressure, and to realize hydrogen recycling. The simplified structure of fuel cell hydrogen supply system is shown in Figure 1-1. The high-pressure hydrogen storage tank is source of hydrogen for system. Hydrogen passes through pressure reducing valve, and pressure is reduced to a suitable range for system. It’s usually about a few bars. The hydrogen intake valve is used to control the amount of hydrogen entering voltaic pile, and then control the pressure of hydrogen circuit of the voltaic pile. Now, the most common hydrogen intake valve is proportional control valve, switching valve or multiple switching valve groups. As the thickness of membrane electrode of fuel cell gradually reduces, its mechanical strength decreases accordingly. Therefore, the dynamic control of the pressure on the air side and the hydrogen side is particularly important for the reliability of the entire fuel cell system. The general requirement is that the pressure on the hydrogen side should be equal to or slightly higher than that air side. When adjusting pressure on both sides, making sure that pressure rises and falls at the same time to reduce the damage to proton membrane. However, in the current hydrogen fuel cell power system, the control of pressure difference between two sides has the following problems: (1) The switching valve is used to control hydrogen intake, which makes fluctuation in the entire hydrogen circuit too large and difficult to control. (2) Although proportional solenoid valve can be used for pressure control which is similar to PID mode according to a certain proportion. However, proportional solenoid valve will bring serious problems of unstable control due to large hysteresis phenomenon. This article will focus on problems exist in hydrogen pressure control of hydrogen fuel cell system, also recommend the use of a precision proportional flow control valve, and introduce characteristics and technical parameters of proportional flow control valve in detail. 2. Proportional flow control valve Proportional flow control valve is shown in Figure 2-1. Model FC-20 FC-120 FC-300 FC-1000 Valve Type Proportional Needle Valve Spool Drift Diameter 0.9mm 2.25mm 2.75mm 4.10mm Actuator Bipolar stepper motor control Response time 0.8sec(Open to close) Standard size G1/8” G3/8” Fluid Inert gas and liquid Contact Materials Stainless Steel Pressure Range -1 ~ 7bar -1 ~ 5bar Maximum Flow 50L/min @7bar 240L/min @7bar 290L/min @7bar 600L/min @7bar   Linearity ±2% ±0.1 ~ 1% ±0.2 ~ 5% ±11% Repeatability (Full scale) ±0.1% Flow Resolution (Step length) 0.1L/min 0.1 ~ 0.2L/min 0.2 ~ 0.75L/min 1L/min Shift Resolution (Step length) 12.7um 25.4um Operating Temperature Range 0 ~ 84ºc Seal Standard FKM or other choices of seals Control Signal DC: 0 ~ 10V (or 4 ~ 20mA) Power Supply DC: 24V (12W) Figure2-2 proportional flow control valve technical indicators. Please visit https://www.genndih.com/proportional-flow-control-valve.htm 2.2. Drive Module The proportional flow control valve is equipped with a stepper motor drive circuit module to provide the required power and control signals, and to convert DC signal into stepper control of bipolar stepper motor, and can also provide direct control of RS485 serial communication. 2.3. Features New proportional flow control valve of digitally controlled motorized for proportional flow regulation combines the precision and repeatability advantages of a stepper motor with the linearity. The resolution is in less than 2% hysteresis, 2% linearity, 1% repeatability and 0.2% adjustable flow control with high performance. It is an upgraded product of commonly used solenoid proportional valve. Combining with various PID control algorithms and pressure controllers, it can form a fast and accurate hydrogen pressure control device. Proportional flow control valve has the following characteristics: (1) Multi-specification throttling area: from the low-flow diameter 0.9mm (0~50L/min gas) to the high-flow diameter 4.10mm (0 to 660 L/min gas) needle valve throttling area, can meet different application needs. (2) High linearity: The linearity of less than 2%. It simplifies surface or matching of external control hardware and software. It also simplifies the relationship between command input and flow output. (3) High repeatability: By reaching the same flow rate of 0.1% each time, it can provide long-term stable consistency. (4) Wide pressure range: With a pressure of 5 or 7 bar, depending on the size of hole, the inlet environment can cover wide pressure range. The stiffness and power of motor ensures that valve opens with the same input command, not about pressure. (5) Low Hysteresis: Hysteresis of less than 2% makes integration and programming simple, providing consistent flow when increasing and decreasing to the set point. (6) High resolution: 0.2% resolution allows proportional flow control valve to perform minimum flow adjustment according to small changes in adjustment command, providing excellent controllability. (7) Quick response: the whole operated time is less than 1 second, which can provide rapid flow regulation and control.

Resumen: En comparación con la válvula de aguja operada manualmente y la válvula proporcional, la válvula de aguja eléctrica tiene las características de control digital, alta sensibilidad, respuesta rápida y pequeña histéresis. Este artículo presenta los productos de sustitución localizados de las válvulas de aguja eléctricas inteligentes desarrollados frente a los productos extranjeros. Este producto no sólo cuenta con el mismo rendimiento del producto, sino también con el bajo costo de alto rendimiento. En comparación con las válvulas de aguja eléctricas nacionales similares, tiene las características de tamaño pequeño y flexibilidad para el desarrollo y la aplicación secundaria. Además, cuando se combina con el ADC de 24 bits, puede lograr una capacidad de regulación precisa del caudal de la válvula de aguja eléctrica. 1. Visión general La válvula eléctrica de aguja es una válvula micro ajustable con un eje de válvula en forma de aguja, que se utiliza principalmente para regular el flujo de aire. El tapón de la válvula en forma de aguja de la válvula de aguja puede hacer que la elevación del puerto de la válvula se haga gradualmente más grande, y puede ser continuamente y meticulosamente regulada desde la potencia hacia arriba y hacia abajo. Como una válvula que puede ser regulada con precisión, la válvula de aguja eléctrica es ampliamente utilizada, y se utiliza principalmente para el ajuste meticuloso y el control del flujo de gas, el nivel de vacío y la presión. Algunos métodos comunes para ajustar la posición de la aguja son los volantes y las manivelas, pero en los procesos de producción de laboratorio y automatización industrial, solemos requerir unas válvulas de aguja con control digital que puedan conectarse a ordenadores y otros instrumentos de control. La apertura de la válvula de aguja puede regularse mediante un control de programación digital. Las válvulas de aguja eléctricas se utilizan en muchos campos, como varios instrumentos analíticos de alta precisión, equipos de proceso de semiconductores, equipos de proceso de vacío y control de flujo de alta precisión. Por otra parte, en comparación con la válvula proporcional, la válvula de aguja eléctrica tiene las características de alta sensibilidad y pequeña histéresis. Por lo tanto, en respuesta a la demanda del mercado de válvulas de aguja eléctricas, KaoLu ha desarrollado una serie de válvulas de aguja eléctricas accionadas por un controlador de motor paso a paso, que tiene el mismo rendimiento de índice técnico pero un rendimiento de bajo coste. En comparación con las válvulas de aguja eléctricas localizadas similares, tiene las características de tamaño pequeño y flexibilidad para el desarrollo y la aplicación secundaria. Combinando nuestra válvula de aguja eléctrica serie FC con un ADC de 24 bits, es posible lograr una resolución extremadamente alta de control de caudal. 2. Comparación de las válvulas eléctricas de aguja existentes, localizadas y fabricadas en el extranjero 2.1 Válvula de aguja eléctrica localizada existente En la actualidad, la válvula de aguja eléctrica nacional adopta generalmente la estructura de añadir un actuador de motor convencional a la válvula de aguja estándar. Un producto típico de esta estructura se muestra en la Figura 2-1. La válvula eléctrica de aguja con una estructura de actuador de motor tiene las siguientes características: ①. La tensión de alimentación es generalmente AC 220V (o DC 24V), y la señal de control es DC 0~10V (o 4~20mA). ②. Los actuadores eléctricos para válvulas de bola y válvulas de mariposa se utilizan generalmente para la referencia, lo que resulta en un enorme volumen. ③. La relación de reducción inherente es generalmente de 50:1, por lo que la precisión de ajuste y control es pobre. ④. El tiempo de respuesta de ajuste es lento, y tiene un grave fenómeno de retraso. El tiempo de conmutación es de al menos 5 segundos. ⑤. El tamaño de la válvula es generalmente grande, y el más pequeño sólo puede llegar a "1/4", que es más adecuado para el ajuste y el control de flujo más grande. ⑥. Toda la resistencia a la presión es alta, lo que es más adecuado para la regulación y el control de alta presión y gran flujo. 2.2 Válvula de aguja eléctrica de fabricación extranjera existente Las válvulas eléctricas de aguja típicas de fabricación extranjera son los productos de INFICON y MKS, como se muestra en la Figura 2-2. El modelo del producto de INFICON es el VDE016, y el producto de MKS es la serie "válvula de control de flujo ascendente" (incluyendo 148J, 154B y 248D). Las características notables de las válvulas de aguja eléctricas de fabricación extranjera son su pequeño tamaño y los módulos independientes para el control del accionamiento, que son muy convenientes para el desarrollo y el uso secundario. La figura 2-3 muestra los principales indicadores técnicos de las válvulas de aguja eléctricas de fabricación extranjera. Modelo INFICON VDE016-X MKS 148J MKS 154B MKS 248D Tipo de válvula Válvula de aguja Controlador Motor paso a paso Bobina electromagnética Tiempo de respuesta (Abrir a cerrar) 3-4 segundos 15ms / 15ms Tamaño estándar KF16 VTF 1/4" Swagelok 1/2" Swagelok 1/4". Materiales de contacto Acero inoxidable Acero inoxidable, PTEF, etc. Acero inoxidable, etc. Acero inoxidable Rango de presión 1×mbar 10bar / 10bar Rango de flujo 3× ~75L/min 0,01 ~ 30L/min 0,2 ~ 200L/min 0,1 ~ 50L/min Linealidad / Resolución de flujo / 0,1 ~ 0,2% de escala completa 0,1% de escala completa 0,1 ~ 2% de escala completa Tamaño de la apariencia (mm) 60×60×152 85×38×100 / 70×38×85 Rango de temperatura de funcionamiento 5 ~ 40c 15 ~ 50c -10 ~ 60c Sello FPM Metal Material elástico Señal de control DC 0 ~ 10V o RS232 DC 0 ~ 10V o 4 ~ 20mA Fuente de alimentación DC24V (12W) DC15 ~ 24V A partir de los indicadores técnicos anteriores, podemos saber que sólo la válvula eléctrica de aguja de INFICON adopta el método controlado por pasos, mientras que los productos de MKS son básicamente válvulas solenoides de aguja típicas, y las válvulas solenoides generalmente tienen un gran fenómeno de histéresis.(Figura 2-3 Principales indicadores técnicos de las válvulas eléctricas de aguja de fabricación extranjera). En comparación con el precio actual, la válvula de aguja eléctrica de INFICON está equipada con un módulo de circuito de accionamiento, y el precio global es de unos 20.000 CNY. El principal producto promocionado actualmente por MKS es la 248D. Su precio es de unos 8.000 CNY, y necesita estar equipado con un módulo de circuito de accionamiento. (unos 5.000 CNY), el precio total es de unos 13.000 CNY. 3. Válvula de aguja eléctrica KaoLu La válvula de aguja eléctrica FC desarrollada por KaoLu es una válvula de aguja dosificadora electrónica inteligente, que cambia la estructura del diámetro de la válvula de aguja manual tradicional y adopta un motor paso a paso lineal de alta precisión para accionar el eje de la válvula. La válvula de aguja eléctrica y su estructura interna se muestran en la Figura 3-1. La resolución del conductor de la válvula proporcional controlada por pasos es de 0,0127mm/paso y 0,0254/paso. La válvula de baja presión diferencial puede funcionar continuamente (relación de trabajo 100%). Un corte de energía es la posición normalmente cerrada de la válvula de aguja eléctrica FC. La mayor ventaja del modo de accionamiento del motor controlado por pasos en comparación con la válvula solenoide es la operación de refrigeración, lo que significa que no hay problemas de operación de control debido al calentamiento de la bobina, una resolución extremadamente alta, una presión diferencial extremadamente baja y una alta presión de funcionamiento. La válvula puede ser controlada por niveles lógicos compatibles con DC 12 VDC y señales analógicas de 0 a 2,5 VDC, o utilizando la intercara RS485 por comunicación directa. Las ventajas resultantes son una histéresis inferior a 2%, una excelente linealidad inferior a 2,5% del fondo de escala, un tiempo de respuesta de 2ms y una vida útil de millones de veces. Visite https://www.genndih.com/proportional-flow-control-valve.htm Modelo FC-20 FC-120 FC-300 FC-1000 Tipo de válvula Válvula de aguja Controlador Control de motor paso a paso bipolar Tiempo de respuesta 0,8seg (de apertura a cierre) Tamaño estándar G 1/8" G 3/8" Fluido Gas inerte y líquido Rango de presión -1 ~ 7 bar -1 ~ 5 bar Rango de flujo 3× ~75L/min 0,01 ~ 30L/min 0,2 ~ 200L/min 0,1 ~ 50L/min Flujo máximo 50L/min @7bar 240L/min @7bar 290L/min @7bar 600L/min @7bar Linealidad 2% 0,1 ~ 1% 0,2 ~ 5% 11% Repetibilidad (escala completa) 1% Resolución de flujo (longitud de paso) 0.1L 0.1 ~ 0.2L 0.2 ~ 0.75L 1L Resolución de desplazamiento 12,7 um 25,4 um Rango de temperatura de funcionamiento 0 ~ 84c Sello FKM estándar u otras opciones de juntas Señal de control DC: 0 ~ 10V (o 4 ~ 20mA) Fuente de alimentación DC: 24V (12W) (Figura 3-2 Principales indicadores técnicos de las válvulas eléctricas de aguja). La serie FC de la válvula eléctrica de aguja está equipada con un módulo de circuito de accionamiento del motor de paso para proporcionar la fuente de alimentación y la señal de control necesarias, y para convertir la señal de CC en el control de paso del motor de paso bipolar. También proporciona un control directo de comunicación por puerto serie RS485. El módulo del circuito de accionamiento, el método de cableado y el tamaño se muestran en la Figura 3-3. 4. Conclusión En resumen, la válvula de aguja eléctrica FC desarrollada por KaoLu adopta la tecnología dinámica de accionamiento del motor paso a paso más avanzada, los indicadores técnicos y superan a los productos extranjeros, también tiene un bajo costo de alto rendimiento.

1. Válvula MKS de control de flujo ascendente Resumen: Basado en las válvulas de control de flujo ascendente de las series 148J, 248A y 154A y en los controladores de las series 244, 250, 946 y 651 de MKS Corporation en Estados Unidos. En este artículo se presentarán los correspondientes productos alternativos localizados de la válvula de aguja de control electrónico y los controladores multifuncionales de alta precisión. Además, se presentan las características e indicadores técnicos correspondientes de los productos sustitutivos localizados. La válvula de control de flujo ascendente MKS es un tipo de válvula proporcional electromagnética de vacío, como se muestra en la figura 1, hay tres series de productos: (1) Válvula de control de flujo 148J totalmente metálica: sello metálico, rango de flujo 0.01~20L/min. (2) Válvula de control de flujo grande 154B: sello de goma, rango de flujo 20~200L/min. (3) Válvula de control de flujo universal 248D: sello de goma, rango de flujo 0.01~50L/min. 2. Controlador de flujo/presión MKS El controlador de flujo/presión de MKS es un tipo de controlador PID, como se muestra en la Figura 2, tiene principalmente las siguientes 4 series de productos: (1) Serie 244: control PID manual, control de un solo canal, adecuado para varios sensores, señal de entrada de 0~10VDC, modo de control manual/automático/externo, la precisión es de 0,25% del fondo de escala, múltiples puntos de ajuste (3 ó 4), indicador de desviación de control. Esta serie de modelos de controlador está descatalogada. (2) Serie 250: control PID manual, control de un solo canal, adecuado para una variedad de sensores de vacío, señal de entrada de 0~10VDC, modo de control manual/automático/externo, la precisión es de 0,25% de escala completa, hasta 4 puntos de ajuste, ajuste de programación externa, indicador digital del valor medido y del valor de desviación de control. Esta serie de modelos de controlador está descatalogada. (3) Serie 946: control PID automático, adquisición A/D de 16 bits, control de 6 canales, adecuado para una variedad de sensores de vacío. Puede controlar hasta 6 señales de sensores al mismo tiempo, señal de entrada/salida de 0~10VDC, modo de control manual/automático/externo, programación interna, pantalla digital del valor medido y del valor de desviación de control, salida de relé de 12 vías, comunicación RS232/485. (4) Serie 651: control PID rápido autorregulado, adquisición A/D de 16 bits, control monocanal, adecuado para una variedad de sensores de vacío, señal de entrada/salida de 0~10VDC, modo de control manual/automático/externo, repetibilidad es escala completa de ±0,1%, programación externa, visualización digital de valores medidos, interfaz de E/S multicanal, comunicación RS232/485. 3. La válvula de aguja localizada y controlada electrónicamente sustituye directamente a la válvula de control de solenoide MKS La válvula de control de flujo aguas arriba de MKS es una válvula solenoide tradicional. El mayor problema de la válvula de solenoide es que la histéresis es relativamente grande, lo que obviamente afectará a la linealidad y a la precisión del control. El precio global de estas válvulas de control es relativamente alto, y no existe una marca local correspondiente. Para lograr la sustitución localizada de las válvulas de control de flujo ascendente y mejorar la eficiencia de los costes, utilizamos motores paso a paso para sustituir a las válvulas de solenoide en la tecnología de válvulas de aguja, y desarrollamos una serie de válvulas de aguja controladas electrónicamente con diferentes caudales. Como se muestra en la Figura 3 y la Figura 4, la sustitución de la localización se ha logrado plenamente. Visite https://www.genndih.com/proportional-flow-control-valve.htm Modelo FC-20 FC-120 FC-300 FC-1000 Tipo de válvula Válvula de aguja Controlador Control de motor paso a paso bipolar Tiempo de respuesta 0,8seg (de apertura a cierre) Tamaño estándar G 1/8" G 3/8" Fluido Gas inerte y líquido Presión Rango -1 ~ 7 bar -1 ~ 5 bar Rango de flujo 3× ~75L/min 0,01 ~ 30L/min 0,2 ~ 200L/min 0,1 ~ 50L/min Flujo máximo 50L/min @7bar 240L/min @7bar 290L/min @7bar 600L/min @7bar Linealidad 2% 0,1 ~ 1% 0,2 ~ 5% 11% Repetibilidad (escala completa) 1% Resolución de flujo (longitud de paso) 0.1L 0.1 ~ 0.2L 0.2 ~ 0.75L 1L Resolución de desplazamiento 12,7 um 25,4 um Rango de temperatura de funcionamiento 0 ~ 84ºc Sello FKM estándar u otras opciones de juntas Señal de control DC: 0 ~ 10V (o 4 ~ 20mA) Fuente de alimentación DC: 24V (12W) 4. El controlador PID localizado de alta precisión sustituye al controlador MKS El control de flujo/presión de gas de MKS es un controlador dedicado, que sólo puede cumplir con el control de flujo y presión de gas en el campo del vacío. Aunque es muy potente, es más caro. El controlador PID sustituido por la localización adopta un colector A/D de 24 bits con mayor precisión. El controlador es más versátil y puede alcanzar el control simultáneo de la temperatura y la presión de vacío, como se muestra en la Figura 5. Las principales características son las siguientes (1) Alta precisión: adquisición A/D de 24 bits, salida D/A de 16 bits. (2) Multicanal: 1 canal y 2 canales independientes. (3) Multifunción: 47 tipos de señales de entrada (termopar, resistencia térmica, tensión continua) pueden alcanzar simultáneamente la comprobación, la visualización y el control de diferentes parámetros, y pueden realizar el control hacia delante y hacia atrás (modo de control bidireccional). (4) Control PID: El algoritmo PID mejorado soporta el control diferencial PV y el control diferencial de avance. 20 grupos de PID de grupo, función de limitador de salida de grupo. (5) Conmutación de sensor dual: Cada canal puede soportar la conmutación de sensor dual de alta y baja temperatura y alto y bajo vacío. Dos canales pueden formar una combinación de control con un total de cuatro sensores conectados. (6) Control de programa: soporta 20 curvas de proceso, cada una con 50 segmentos, soporta ciclo interno y ciclo de curva.

Un tutorial detallado sobre el grado de vacío y el método de control de la temperatura en la caja de guantes Resumen: Con el fin de alcanzar potentes funciones de la caja de guantes para dos variables ambientales de vacío y temperatura en la caja de guantes. Este artículo se centra en la solución integrada para la medición y el control precisos del vacío y la temperatura, y describe los métodos ascendentes, descendentes y bidireccionales. También presenta la aplicación específica del modo de control de conmutación en diferentes rangos de grado de vacío, y demuestra la nueva válvula de control de flujo proporcional y el controlador PID de ultra alta precisión de 24 bits utilizado en el control. 1. Preguntas Las cajas de guantes de vacío se utilizan a menudo para sustancias fácilmente oxidables y delicuescentes. Las reacciones químicas, el procesamiento de materiales y las pruebas de rendimiento que requieren operaciones manuales en un entorno anaeróbico y anhidro son muy útiles. La función principal de la caja de guantes es proporcionar un entorno de vacío y fácil de usar, pero en las aplicaciones prácticas actuales la mayoría de las cajas de guantes sólo utilizan el entorno anaeróbico y las funciones de operación manual de la caja de guantes, y no dan plena capacidad al papel de la caja de guantes. La aplicación más potente de la caja de guantes también se refleja en los dos aspectos siguientes: (1) La caja de guantes de vacío es una caja ambiental hermética, y el grado de vacío final puede alcanzar generalmente alrededor de 10Pa, por lo que el grado de vacío en la caja de guantes puede ser controlado en cualquier punto de ajuste entre 10Pa y la presión atmosférica según sea necesario. Se pueden llevar a cabo varias reacciones químicas, experimentos y pruebas que son sensibles al vacío; también se pueden llevar a cabo varias operaciones manuales sin cambiar ni destruir el entorno de vacío. (2) Además del vacío, la temperatura es otra variable ambiental importante para muchas reacciones, experimentos y pruebas. Colocando el correspondiente dispositivo de calentamiento en la caja de guantes, se pueden realizar diversos estudios experimentales bajo el entorno combinado de temperatura y grado de vacío. Y así sucesivamente, también se pueden configurar otras condiciones ambientales de cantidades físicas para formar condiciones de prueba de acoplamiento de cantidades físicas múltiples bajo diversas condiciones de contorno. Con el fin de lograr el pleno rendimiento de una caja de guantes de vacío, se centra en dos variables ambientales de grado de vacío y la temperatura en la caja de guantes. Este artículo presenta en detalle la solución integrada para la medición y el control precisos del grado de vacío y la temperatura, e introduce los diferentes rangos de grado de vacío de los modos de control ascendente, descendente y bidireccional en el proceso de control del vacío. 2. Control de vacío en la caja de guantes La caja de guantes pertenece a una cavidad de bajo vacío. El grado de vacío de la caja de guantes utilizando una bomba mecánica puede alcanzar generalmente una presión absoluta de unos 10Pa. Mediante el vacío y el llenado con gas inerte, el grado de vacío de la guantera puede controlarse desde 10Pa hasta una atmósfera (presión absoluta de 0,1MPa). Para el control en tal rango de vacío que abarca cuatro órdenes de magnitud, se utilizarán sensores de vacío con diferentes precisiones según las necesidades reales, y habrá diferentes modos de control en consecuencia. A continuación se presenta el contenido específico de cada modo de control. 2.1 Modo de control ascendente Como se muestra en la Figura 1, bajo la condición de que las velocidades de bombeo de la bomba de vacío aguas abajo se mantienen constantes. El modo de control aguas arriba consiste en ajustar la apertura de la válvula de control de flujo proporcional del puerto de entrada de aire aguas arriba a través del controlador de presión de vacío PID de acuerdo con la señal de medición del vacuómetro, es decir, controlando el flujo de entrada para mantener la presión en la guantera en el punto de ajuste. El modo aguas arriba se utiliza a menudo para el control de alto vacío. 2.2 Modo de control descendente Como se muestra en la Figura 2, bajo la condición de que la velocidad de bombeo de la bomba de vacío aguas abajo se mantiene constante, el modo de control aguas abajo consiste en ajustar la apertura de la válvula de control de flujo proporcional de la salida de aire aguas abajo a través del controlador de presión de vacío PID de acuerdo con la señal de medición del vacuómetro, es decir, mediante el control del flujo de aire, la presión en la guantera se controla en el valor establecido. Podemos ver que el modo aguas abajo se utiliza a menudo para el control de bajo vacío. 2.3 Modo de control bidireccional Los modos de control aguas arriba y aguas abajo mencionados anteriormente tienen sus propias ventajas, y rara vez se utilizan solos en las aplicaciones prácticas. Por lo general, los modos aguas arriba y aguas abajo se integran juntos, lo que constituye el llamado modo de control bidireccional, como se muestra en la Figura 3. En el modo de control bidireccional, se requiere que el controlador de presión de vacío tenga funciones de control hacia adelante y hacia atrás, es decir, control inverso para la válvula de control de flujo proporcional aguas arriba y control inverso para la válvula de control de flujo proporcional aguas abajo. 2.4 Modo de conmutación automática del sensor doble Como se ha mencionado anteriormente, si la medición y el control precisos del grado de vacío se llevan a cabo en el rango completo de 10Pa~0,1MPa, generalmente es necesario configurar dos manómetros de diafragma de alta precisión de 1000Torr y 10Torrswitch automáticamente. Como se muestra en la figura 4, el punto de conmutación alto (2-3) es el punto alto donde funciona el sensor de bajo vacío, y el punto de conmutación bajo (1-2) es el punto bajo donde funciona el sensor de alto vacío. El controlador realiza el cálculo de suavización entre estos dos puntos. Cuando el muestreo continuo de la medición de bajo vacío PV1 y de la medición de alto vacío PV2 está por debajo del punto de conmutación inferior, se cambia al sensor de vacío grueso. Cuando el muestreo continuo del valor medido de bajo vacío PV1 y el valor medido de alto vacío PV2 está por encima del punto de conmutación superior, se realiza la conmutación al sensor de alto vacío. 3. Selección del vacuómetro, la válvula y el controlador 3.1 Selección del sensor de vacío Al igual que otros sensores, los distintos sensores de vacío también tienen un determinado rango de medición y precisión. La regla básica es que un sensor con un amplio rango de medición tiene poca precisión; un sensor con alta precisión de medición tiene un rango de medición más estrecho. En el caso de la caja de guantes, como se muestra en la figura 5, los sensores de vacío utilizados suelen tener las tres categorías siguientes: (1) Vacuómetro convencional: Medidor de vacío Pirani, la precisión es de ±(15~50)% de la escala completa, pero un medidor de vacío puede cubrir la escala completa. (2) Vacuómetro de alta precisión: manómetro de diafragma, la precisión es de ±2,5% de la escala completa, si cubre el rango de 10Pa~0,1MPa, generalmente se requieren dos vacuómetros de 1000Torr y 10Torr. (3) Medidor de vacío de ultra alta precisión: medidor de vacío para semiconductores, la precisión es de ±0,05% de la escala completa, y el rango efectivo es de 50Pa ~ 0,1MPa, que no puede cubrir un vacío más alto. 3.2 Selección de la válvula eléctrica En la guantera de control de vacío, generalmente hay dos tipos de válvulas: una es una válvula de entrada de aire que ajusta el flujo en la entrada de aire, y la otra es una válvula de escape que ajusta el flujo de escape. Las válvulas de admisión de aire se utilizan sobre todo para la regulación de pequeños caudales, por lo que generalmente se seleccionan válvulas de aguja. Las válvulas de escape se utilizan sobre todo para la aspiración, por lo que generalmente se requieren válvulas de bola de mayor diámetro. Debido al control automático, tanto las válvulas de aguja como las de bola deben ser accionadas por tensión continua, corriente continua o señal digital (RS485), lo que constituye la llamada válvula de control de flujo proporcional. La válvula de control de flujo proporcional selecciona una válvula de control de flujo proporcional accionada por un motor de pasos de pequeño tamaño, como se muestra en la Figura 6. Esta válvula de control de flujo proporcional tiene una alta velocidad de respuesta (dentro de 1s) y linealidad (dentro de 1%). Para la válvula de control de flujo proporcional de la serie FC, visite https://www.genndih.com/proportional-flow-control-valve.htm 3.2 Selección del controlador A partir de los diferentes modos de control del grado de vacío de la guantera, se puede ver que el proceso de control del grado de vacío plantea altos requisitos para el controlador. Como se muestra en la Figura 7, el controlador seleccionado debe cumplir los siguientes criterios: (1) Al menos es un controlador PID, y tiene la función de autoajuste de parámetros PID. (2) La precisión del propio vacuómetro es alta. Para dar todo el juego a la precisión de la medición del vacuómetro, el controlador PID que necesita la adquisición de datos y el control debe tener una alta precisión. Se recomienda que el controlador tenga una adquisición A/D de 24 bits y una salida D/A de 16 bits. (3) Se requieren al menos 2 canales para lograr la medición y el control simultáneo de la temperatura y el grado de vacío, también para reducir el espacio de instalación. (4) Funciones de acceso a múltiples señales de entrada, que pueden conectar directamente las señales de entrada de diferentes tipos de sensores como termopar, resistencia térmica, tensión continua, etc., para lograr la comprobación, visualización y control simultáneos de diferentes parámetros. (5) Función de control de avance y retroceso para alcanzar el modo de control bidireccional. (6) Con la función de conmutación de sensor dual, cada canal puede soportar la conmutación de sensor dual de alta y baja temperatura y alto y bajo vacío. Dos canales pueden formar una combinación de control con un total de cuatro sensores conectados. (7) Función de control de programa, puede crear y guardar múltiples programas de control por sí mismo, y sólo necesita seleccionar y llamar para iniciar (modo de control de programa). (8) Dispone de una interfaz de comunicación para conectar con el ordenador, como la interfaz RS485 del protocolo estándar MODBUS. 4. Control de la temperatura de la caja de guantes Además de proporcionar un entorno de vacío, la caja de guantes también puede poner un dispositivo de calefacción en la caja de guantes para realizar diversos experimentos y pruebas a diferentes temperaturas, por lo que es necesario introducir la función de control de temperatura en la aplicación de la caja de guantes. El control de temperatura es una tecnología muy madura y clásica, que generalmente se realiza utilizando un controlador PID en combinación con un sensor de temperatura. Con el fin de reducir el coste y el volumen de instalación, generalmente se utiliza un controlador PID multicanal para controlar la temperatura y el grado de vacío al mismo tiempo. El controlador se comunica con un ordenador para mostrar y almacenar los datos de control y las curvas de medición. Por lo general, no se requiere que la temperatura de trabajo en la caja de guantes sea demasiado alta, pero si la protección térmica y el enfriamiento se hacen bien, también se puede lograr el rango de temperatura de trabajo por encima de 1000°C. El sensor de medición de la temperatura suele elegir un termopar. Si la precisión de la medición es alta, también se puede elegir la resistencia térmica y el sensor de temperatura de termistor. Estos sensores se pueden conectar directamente al controlador PID de alta precisión mencionado anteriormente. 5. Conclusión A través de la introducción del contenido anterior, se explican básicamente los diversos métodos de control del grado de vacío y la temperatura en la guantera y los principales sensores, la válvula de control de flujo proporcional y los controladores PID involucrados. En aplicaciones específicas, se pueden realizar mejoras parciales en la estructura y función específicas de la caja de guantes, y el diseño general, la instalación y la integración de la caja de guantes también pueden llevarse a cabo de acuerdo con los requisitos reales. Aunque este artículo sólo introduce la medición y el control del grado de vacío y la temperatura en la caja de guantes, estos métodos y contenidos específicos de implementación también pueden extenderse y aplicarse al control de los parámetros de prueba en otros campos que son más sensibles al entorno de la atmósfera, como la baja temperatura, la cantidad geométrica, la óptica y la acústica.

Sustitución localizada de las válvulas de control de gas VDE016 de INFICON y EVR116 de Pfeiffer y de los controladores PID Resumen: No sólo se compara con la VDE 016 de INFICON y la válvula de control de gas EVR 116 de Pfeiffer, sino con la VCC500 de INFICON y el controlador RVC 300 de Pfeiffer. Este artículo presenta los correspondientes productos alternativos localizados válvula electrónica de control de flujo de aire y multi-función de controlador PID de alta precisión. También presenta las características correspondientes y los indicadores técnicos de los productos alternativos localizados. 1. Visión general La válvula de control de gas VDE 016 de INFICON y la EVR 116 de Pfeiffer son en realidad exactamente la misma válvula de control, sólo que el OEM es diferente. Como se muestra en la figura 1, esta válvula de control de gas es una válvula de aguja accionada por un motor paso a paso, que puede convertir una señal de control externa en una posición prescrita de la aguja de la válvula, ajustando así la apertura de la válvula para alcanzar el control del flujo de gas. La señal de control externa puede ser de los siguientes tres tipos : (1) Tensión de simulación DC (0~10VDC) (2) Módulo de interfaz (3) Interfaz RS232 Para esta válvula de control de gas, INFICON y Pfeiffer proporcionaron los controladores correspondientes, como se muestra en la Figura 2, los modelos son: INFICON: VCC500-Z; Pfeiffer: RVC 300. En este artículo se presentarán los indicadores técnicos correspondientes a las válvulas de control y los controladores mencionados, y se presentarán los productos alternativos correspondientes localizados y sus indicadores técnicos, con el fin de proporcionar productos rentables para la sustitución localizada. 2. Indicadores técnicos de los productos extranjeros 2.1 Especificaciones de la válvula de control de gas Los parámetros de rendimiento de las válvulas de control de INFICON y Pfeiffer se muestran en la Tabla 1, y los indicadores técnicos se muestran en la Tabla 2. 2.2 Indicadores técnicos del controlador Los indicadores técnicos del rendimiento del controlador de INFICON y Pfeiffer se muestran en la Tabla 3. Modo de funcionamiento Control de la presión, regulación del flujo de gas Salida analógica 4 canales: señal del sensor de presión de vacío, señal de la válvula (0-10VDC), posición de la válvula, tensión de referencia de +10VDC (10mA) Salida numérica 8 canales: válvula abierta, válvula cerrada, posición de la válvula, error de la válvula, error del sensor, preparación, divergencia, estado del sensor Entrada analógica 2 canales: punto de ajuste de la presión de vacío (valor estándar), punto de ajuste del flujo (valor estándar) Entrada numérica 8 canales: reducción de flujo, adición de flujo, cierre externo, apertura externa, modo de flujo, modo de presión, apertura de descarga, apertura de escape Característica Después de un corte de energía, enciende la salida "alcanza el valor estándar", entonces puede ajustar la tolerancia Unidad de visualización mbar, Pa, Torr, mV Idioma Inglés, alemán Interfaz de comunicación RS232C, RS485 Tipo de controlador PI automático: puede elegir el paso de velocidad de control 1-99 PID: el usuario puede definir los parámetros Precisión de control ±5% Sensor FS Precisión de la pantalla ±0,2% Sensor FS Fuente de alimentación Tensión90 ~250VAC Peso 1,65 kg A partir de los indicadores técnicos de los controladores mencionados y de la experiencia de aplicación práctica, se puede constatar que los controladores INFICON y Pfeiffer tienen las siguientes deficiencias (1) Medición y control de un solo canal: es decir, sólo se puede recoger una señal de manómetro de vacío y una válvula de control. Aunque hay múltiples canales de entrada y salida analógicos y digitales, sólo se puede realizar un control en bucle cerrado. Este controlador de un solo canal no podrá cubrir el amplio rango que requieren dos vacuómetros. (2) No hay función de autorregulación PID: La mayor desventaja de los controladores INFICON y Pfeiffer es la falta de la función de autorregulación de los parámetros PID, lo que trae inconvenientes en las aplicaciones prácticas, requiriendo que los usuarios encuentren los parámetros PID adecuados por sí mismos. A veces los parámetros PID óptimos no se pueden obtener al final, lo que afecta seriamente el efecto de control. (3) Poca precisión de control: La precisión de control es de ±5% de la escala completa del sensor, lo que muestra básicamente que el circuito de adquisición y control en el controlador utiliza convertidores A/D y D/A de 12 bits, que es la clave para determinar la precisión de control. 3. La válvula electrónica de control de flujo de aire de KaoLu sustituye a las válvulas de control de INFICON y PFA La válvula de control de INFICON y Pfeiffer es una típica válvula electrónica de control de flujo de aire accionada por un motor paso a paso. El indicador de rendimiento es muy superior. La única desventaja es que la apertura de la válvula de aguja es pequeña, por lo que provoca un flujo pequeño. Además, el precio es demasiado caro. Con el fin de alcanzar la sustitución de la válvula de control de flujo de gas y mejorar el bajo costo de alto rendimiento, KaoLu también utilizó el motor paso a paso en la tecnología de la válvula de aguja para la localización, y desarrolló una serie de válvula electrónica de control de flujo de aire con diferentes tasas de flujo. Como se muestra en la figura 3, se ha sustituido por completo, y el precio es sólo un tercio de los productos extranjeros. Los indicadores técnicos detallados se muestran en la figura 4. Por favor, visite https://www.genndih.com/proportional-flow-control-valve.htm (Figura3 Válvula electrónica de control de flujo de aire FC de KaoLu) Modelo FC-20 FC-120 FC-300 FC-1000 Tipo de válvula Válvula de aguja Diámetro de deriva del carrete 0,9mm 2,25mm 2,75mm 4,10mm Actuador Control de motor paso a paso bipolar Tiempo de respuesta 0,8seg (de abierto a cerrado) Tamaño estándar G1/8" G3/8" Fluido Gas inerte y líquido Materiales de contacto Acero inoxidable Rango de presión -1 ~ 7bar -1 ~ 5bar Caudal máximo 50L/min @7bar 240L/min @7bar 290L/min @7bar 600L/min @7bar Linealidad ±2% ±0,1 ~ 1% ±0,2 ~ 5% ±11% Repetibilidad (escala completa) ±0,1% Resolución de flujo (longitud de paso) 0,1L/min 0,1 ~ 0,2L/min 0,2 ~ 0,75L/min 1L/min Resolución de cambio (longitud de paso) 12,7um 25,4um Rango de temperatura de funcionamiento 0 ~ 84ºc Sello FKM estándar u otras opciones de juntas Señal de control DC: 0 ~ 10V (o 4 ~ 20mA) Fuente de alimentación DC: 24V (12W) (Figura4 Indicadores técnicos de la válvula electrónica de control de flujo de aire FC de KaoLu) 3. El controlador PID localizado de alta precisión de doble canal sustituye a los controladores INFICON y PFA Para aprovechar al máximo la precisión de las mediciones de los manómetros de vacío (como los manómetros de película capacitiva), se necesitan convertidores analógico-digital y digital-analógico de al menos 16 bits para la adquisición de datos y el control del controlador. En los últimos años, KaoLu ha desarrollado la serie FC de controladores PID de alta precisión y 24 bits de uso general, como se muestra en la figura 5. Esta serie de controladores PID es mucho más potente que los productos extranjeros, pero el precio es sólo una octava parte de los productos extranjeros. Sus principales indicadores de rendimiento son los siguientes (1) Precisión: A/D de 24 bits, D/A de 16 bits. (2) Multicanal: 1 o 2 canales independientes. Los 2 canales pueden realizar la medición y el control simultáneos de la temperatura y la presión. (3) Variedad de parámetros de salida: 47 tipos de señales de entrada (termopar, resistencia térmica, voltaje DC) pueden alcanzar la prueba simultánea, la visualización y el control de diferentes parámetros. (4) Multifunción: control bidireccional de avance, retroceso, avance y retroceso. (5) Control PID: El algoritmo PID mejorado soporta el control diferencial PV y el control de avance diferencial. Hay 20 grupos de PID. (6) Conmutación de sensor dual: Cada canal puede soportar la conmutación de sensor dual de alta y baja temperatura y alto y bajo vacío. Dos canales pueden formar una combinación de control con un total de cuatro sensores conectados. (7) Control de programa: Puede crear y almacenar hasta 20 programas de condensación por sí mismo, y sólo tiene que seleccionar y llamar para iniciar la condensación (modo de control de programa). En el control del grado de vacío, el modo de control aguas abajo es más adecuado para el grado de vacío cercano a la presión atmosférica, pero el modo de control de entrada de aire aguas arriba es necesario para el control del grado de vacío de menos de 10mbar. Por lo tanto, para satisfacer el grado de control de vacío completo, se puede utilizar el sensor doble y el modo de control de dos vías como se muestra en la Figura 6. En el modo de control mostrado en la Figura 6, es necesario utilizar las funciones de control de avance y retroceso y de conmutación automática del sensor doble del controlador de doble canal de la serie FC-20 anterior, es decir, durante los diferentes procesos de control de la presión del aire; el controlador conmuta automáticamente el rango correspondiente. El medidor de vacío, y selecciona la válvula electrónica de control de flujo de aire correspondiente para el control.

Resumen: Centrándose en el control de alta precisión del medio de baja temperatura en el criostato, este artículo presenta principalmente el método de descompresión y control de la temperatura del medio de baja temperatura y la influencia de la precisión del control de la presión del aire en la estabilidad de la baja temperatura. Tres modos de calentamiento, control de flujo y control de presión, así como las correspondientes condiciones de trabajo específicas que incorporan la válvula eléctrica neumática de control de flujo y los detalles. 1. Introducción En el criostato, la razón principal de la fluctuación de la temperatura del medio criogénico (helio líquido y nitrógeno líquido, etc.) es el cambio de presión (vacío) en la parte superior del medio criogénico en ebullición. Por lo tanto, para alcanzar una temperatura estable dentro del medio criogénico, es necesario controlar con precisión la presión del aire en la parte superior del medio criogénico. El control internacional y localizado de la temperatura de los criostatos adopta mayormente los siguientes tres enfoques técnicos: (1) Método de control activo: El circuito de calefacción entra directamente en la cámara de vacío sumergida en el medio de baja temperatura, y los datos de monitorización de la temperatura en tiempo real de la cámara de vacío se utilizan para comparar con el valor de la temperatura objetivo y luego controlar la corriente añadida al circuito de calefacción. (2) Método de control pasivo: Controlar la presión del aire en la parte superior del medio de baja temperatura para estabilizar la temperatura del medio de baja temperatura. (3) Método de control compuesto: Los dos métodos de control anteriores se combinan, y el circuito de control de la calefacción conduce directamente a la cámara de vacío inmersa en el medio de baja temperatura, y la presión del aire por encima del medio de baja temperatura también se controla al mismo tiempo. El método de control de temperatura por calentamiento por resistencia es ya una tecnología muy madura. Este artículo se centrará principalmente en el método de control de la presión en la parte superior del medio de baja temperatura, e introducirá la influencia de la precisión del control de la presión en la estabilidad de la baja temperatura, así como el método de realización y el esquema específico del control de la presión de alta precisión. 2. La relación entre la precisión del control de la presión del aire y la estabilidad de la temperatura Tomando el hidrógeno líquido como ejemplo, la presión de vapor saturado del hidrógeno líquido y la correspondiente curva de cambio de temperatura se muestran en la Figura 1. Como puede verse en la Figura 1, en un rango de temperatura muy pequeño, la curva anterior puede describirse mediante una línea recta, por lo que puede obtenerse en un rango de temperatura de unos 4K; la fluctuación de la presión del aire de unos 100Pa puede causar una fluctuación de temperatura de unos 1mK. Por lo tanto, se puede considerar que si se quiere alcanzar una fluctuación inferior a 1mK, la fluctuación de la presión atmosférica no puede superar los 100Pa. 3. Tres modos de control de la presión del aire superior En general, existen tres modos de control de la presión del aire en la parte superior del medio criogénico: calentamiento por resistencia, control del flujo y control de la presión. 3.1 Modo de calentamiento por resistencia En el proceso de control de temperatura constante del criostato, el modo de calentamiento por resistencia consiste en colocar un calentador de hilo de resistencia en el medio de baja temperatura. Como se muestra en la Figura 2, el vacuómetro detecta el cambio de la presión del aire en la parte superior, y el controlador PID cambia la corriente de calentamiento para ajustar y controlar la presión del aire en la parte superior, manteniendo la presión del aire en la parte superior constante en el valor establecido. En la figura 2 se puede observar que el modo de calentamiento por resistencia es más adecuado para el método de control de la temperatura de aumento de la presión en la parte superior, pero no puede reducir la presión y la refrigeración. 3.2 Modo de control de flujo El modo de control de flujo es un modo típico de reducción de presión y refrigeración. Como se muestra en la figura 3, la bomba de vacío extrae continuamente el criostato a una determinada velocidad de bombeo para reducir la presión del aire superior. El vacuómetro, la válvula neumática electrónica de control de flujo y el controlador PID forman un bucle de control cerrado. La válvula electrónica de control de flujo neumático de la serie FC ajusta el flujo de aire para mantener la presión de aire superior de forma precisa y constante en el grado de vacío. Se puede observar que el modo de control de flujo es más adecuado para el método de refrigeración y control de temperatura para reducir la presión del aire superior, pero no puede alcanzar la sobrealimentación y la calefacción. Además, en el modo de control de flujo, el bombeo continuo de la bomba de vacío hace que la disipación ineficaz del medio de baja temperatura sea más grave. Para más información sobre la válvula electrónica de control de flujo neumático de la serie FC, visite https://www.genndih.com/proportional-flow-control-valve.htm. 3.3 Modo de control de presión El modo de control de presión es un modo de control de temperatura que puede aumentar o disminuir la presión. Como se muestra en la Figura 4, cuando se adopta la bomba de vacío para evacuar es el modo de reducir la presión. Cuando se adopta la bomba de refuerzo es el modo de aumentar la presión. De este modo, se puede alcanzar un control continuo de la temperatura en una amplia zona de temperatura. El regulador de presión proporcional utilizado viene con una entrada de aire (presión atmosférica). En combinación con la bomba de vacío, puede evitar eficazmente una gran cantidad de disipación ineficaz del medio de baja temperatura mientras se controla la presión superior a una presión constante. Además, el método de sobrealimentación aquí también se puede alcanzar añadiendo un calentador eléctrico al medio de baja temperatura. 4. Detalles adicionales de funcionamiento Durante la implementación de los tres modos de control anteriores, se debe tener en cuenta específicamente los siguientes detalles: (1) Selección del vacuómetro El vacuómetro es un sensor que mide el cambio en la presión del aire en la parte superior. La clave para determinar la estabilidad del control de la temperatura del criostato, por lo que hay que asegurarse de elegir un vacuómetro de alta precisión. En la actualidad, los vacuómetros de alta precisión son generalmente medidores de película capacitiva, y la precisión general es de 0,2%. Como se ha mencionado anteriormente, en el proceso de control de la temperatura constante del hidrógeno líquido alrededor de 4K, se requiere que la fluctuación de la presión del aire no exceda de 100Pa, y ±50Pa. Si corresponde a un control de la presión del aire de 100kPa, la precisión del vacuómetro debe ser superior a ±0,05%. Se puede ver que el control de la temperatura constante con la fluctuación de la temperatura menos de 1mK, también se requiere un medidor de vacío de mayor precisión. (2) Selección del controlador PID En el proceso de control de temperatura constante, el controlador PID recoge el valor medido del vacuómetro a través del convertidor A/D, y luego envía la señal de control al actuador (válvula de aguja eléctrica, regulador de presión y fuente de alimentación de la calefacción, etc.) a través del convertidor D/A después del cálculo. ). Por esta razón, para asegurar que la alta precisión y exactitud de control del vacuómetro puede ser totalmente utilizada y regulada con una válvula electrónica de control de flujo neumático, cuanto más alta sea la precisión de los convertidores A/D y D/A, mejor al menos 16 bits, y se recomienda encarecidamente un controlador PID de alta precisión de 24 bits. (3) Asignación del regulador de tensión El regulador de presión es un dispositivo de control de presión que integra un sensor de presión de vacío, un controlador y una válvula, pero la precisión del sensor de presión de vacío es mucho menor que la del condensador de película fina, y la precisión del controlador también es relativamente baja. Por lo tanto, cuando se utiliza un regulador de tensión, se debe seleccionar un modo de control externo, es decir, se utiliza un condensador de película fina como sensor de control. Además, hay que tener en cuenta que los convertidores A/D y D/A del controlador en el regulador tienen una baja precisión. Por lo tanto, para el control de la presión de aire superior de alta precisión y alta estabilidad, no se recomienda el modo de control de la presión, a menos que se utilice un regulador de tensión de alta precisión fabricado especialmente.

Resumen: La medición espectral y el espectrómetro son medidas técnicas importantes en la detección y el control. Para obtener una precisión de medición satisfactoria, el espectrómetro requiere transductores de presión y temperatura de alta precisión, actuadores y controladores PID, y debe tener las características de una amplia gama de aplicaciones, alta precisión, fácil integración y bajo coste. Este artículo se centrará en las características del control de la presión y la temperatura del espectrómetro, en combinación con los innovadores productos de la válvula de aguja electrónica de la serie FC de KaoLu. También ofrece un programa de medición del espectro de alta precisión y bajo coste, de medición y control de la temperatura y la presión del espectrómetro. 1. La formulación de la pregunta Como método de análisis científico cualitativo y cuantitativo, la medición espectral se ha convertido en una medida técnica importante en diversas investigaciones de detección y control debido a sus ventajas de alta precisión de medición y rápida velocidad de respuesta. Sin embargo, en las aplicaciones prácticas, los cambios de presión y temperatura del gas de muestra afectarán a los resultados de la medición. A continuación se presentan algunos de los trabajos de investigación realizados en el país y en el extranjero sobre el control de la temperatura y la presión en la medición espectral y las características del impacto: ①. Rango de control de la presión Diferentes espectrómetros y espectrómetros tienen diferentes requisitos para el rango de control de la presión. Por ejemplo, la espectroscopia de infrarrojos que utiliza la cureña de gas, la intensidad del pico de absorción se puede lograr mediante el ajuste de la presión del gas de la muestra. El rango de presión general es de 0,5 ~ 60kPa. Cuando se utiliza la tecnología de espectroscopia de absorción láser de diodo sintonizable (TDLAS) para medir la concentración de dióxido de carbono en la atmósfera, se requiere una presión estable en el rango de 6~101kPa. En el control preciso de la presión dentro del detector del espectrómetro de rayos X, la densidad del gas de trabajo debe estabilizarse para garantizar la precisión de la medición del detector. Generalmente, la presión debe ser controlada en torno a una presión atmosférica o superior, mientras que la presión de trabajo del espectrómetro de ruptura inducida por láser debe ser de hasta 275kPa. Se puede observar que el rango de control de la presión del gas de trabajo en el espectrómetro es relativamente amplio, generalmente en el rango de 0,1~300kPa, que básicamente cubre el rango de presión de 4 órdenes de magnitud desde la presión negativa del vacío hasta 3 veces la presión atmosférica. ②. Precisión del control de la presión En la prueba de espectros, la relación entre la intensidad de la línea espectral observada y la densidad real del gas depende de la presión de la muestra de gas, por lo que la precisión del control de la presión determina directamente la precisión de la medición espectral. Por ejemplo, la precisión del control de la presión en el analizador de espectros de la empresa Picarro es de ±0,0005 atmósferas (tasa de fluctuación de ±0,05%@1 atmósfera de presión). En la literatura [1] se informa de que el tanque de absorción se controló cuando la presión establecida era de 6,67kPa. Tras cuatro horas de control continuo, la fluctuación de la presión era de ±3,2Pa, y la tasa de fluctuación era de ±0,047%. La literatura [2] informó que cuando la presión del gas en una celda de muestra también se controló a 6,67kPa, el rango de fluctuación a largo plazo de la presión fue de 7Pa, y la tasa de fluctuación fue de ±0,047%. La literatura [3] informó de la medición de la estabilidad del sistema de control de la presión de la célula de paso múltiple por láser. La presión objetivo se fijó en 60 Torr, la fluctuación máxima fue de ±0,04 Torr en 150~200s, y la tasa de fluctuación fue de ±0,067%. La literatura [4] informó especialmente sobre el diseño y la investigación del sistema de control de temperatura y presión de alta precisión del instrumento de medición espectroscópica. El valor de la presión objetivo es de 18,665kPa, el control de la presión constante durante 42 horas, la desviación máxima es de 5,33Pa, y la tasa de fluctuación es de ±0,014%. La literatura [5] introdujo los resultados del control de presión constante del detector en el espectrómetro de rayos X. Durante la presión constante del gas de trabajo a 940 hPa, la fluctuación fue inferior a ± 2 hPa, y la tasa de fluctuación fue de ± 2%. La literatura [6] introdujo la tecnología de control de presión constante del espectrómetro fotoeléctrico de rayos X en el rango de presión de 0,05~30mbar. Cuando el valor establecido es de 0,1mbar, la precisión constante puede alcanzar ±0,001mbar, y la tasa de fluctuación es de ±1%. ③. Precisión del control de la temperatura En la prueba de espectros, la relación entre la intensidad de la línea espectral y la densidad real del gas también depende de la estabilidad de la temperatura de la muestra de gas. La estabilidad de la temperatura también afectaría a la estabilidad de la presión. La literatura [2] informó que la temperatura del gas en la celda de la muestra se controló a temperatura ambiente (24°C), la fluctuación de la temperatura a corto plazo es de ±0,01°C, la deriva de la temperatura a largo plazo es de ±0,025°C, y la tasa de fluctuación es de ±0,1%. En la literatura [4] se informa de que el sistema de control de temperatura de alta precisión del espectrómetro, la temperatura se controla a 45°C, y la fluctuación de temperatura en 42 horas es de ±0,0015°C, y la tasa de fluctuación es inferior a ±0,004%. En resumen, los cambios de presión y temperatura del gas de muestra son los principales factores que afectan a los resultados de la medición. Por lo tanto, en la medición espectral y en varios espectrómetros, el ajuste y control de la presión y la temperatura del gas de muestra tiene los siguientes requisitos: (1) El rango de control de la presión es muy amplio (0,1~300kPa), pero la precisión de medición y control correspondiente es realmente alta, lo que hace que se exijan mucho los sensores de medición de la presión, las válvulas de control, las bombas de vacío y los controladores correspondientes. Estos cuatro componentes de este sistema de control de bucle cerrado deben coincidir entre sí; de lo contrario, es difícil obtener resultados satisfactorios. (2) Del mismo modo, en el proceso de control de temperatura de alta precisión, los sensores de temperatura, los dispositivos de calentamiento, la fuente de alimentación y el controlador correspondientes deben coincidir. Estos cuatro componentes en el sistema de control de lazo cerrado de temperatura también deben coincidir entre sí. (3) Se utilizarán controladores de alta precisión en los dos sistemas de control de bucle cerrado de presión y temperatura. Para reducir el coste experimental y el coste del espectrómetro, queremos utilizar un controlador de alta precisión con 2 funciones de control automático PID simultáneas. (4) Al centrarse en diferentes mediciones espectrales y espectrómetros, sus estructuras de prueba no son las mismas, lo que requiere la independencia de cada componente en el sistema de control de la temperatura y la presión. De esta manera, es beneficioso para la integración del dispositivo de prueba y el espectrómetro. En general, para obtener la exactitud satisfecha de la medición espectral, se requieren sensores y actuadores de presión y temperatura de alta precisión.Tiene las características de amplio rango de aplicación, alta precisión, fácil integración y bajo costo. Este artículo se centrará en estas características, se combinará con los productos innovadores de KaoLu y proporcionará una medición espectral de alta precisión y rentable y un plan de medición y control de la temperatura y la presión del espectrómetro. 2. Método de medición y control integrado de la presión y la temperatura del espectrómetro 2.1 Diseño del modo de control (1) Modo de control de la presión Como se ha mencionado anteriormente, para el rango de control del espectrómetro (0,1~300kPa), la mejor solución es seleccionar el modo de medición y control correspondiente según el rango de presión específico utilizado. Como se muestra en la Figura 2-1, se recomienda utilizar el modo de control ascendente para el rango de baja presión. Para el rango de alta presión, se adopta el modo de medición y control aguas abajo; también puede adoptar el modo de control bidireccional de control simultáneo aguas arriba y aguas abajo. Figura 2-1 Tres modos de control de la presión El modo de control aguas arriba se adopta para la baja presión, que puede ejercer repetidamente la velocidad de bombeo de la bomba de vacío, de modo que la presión en la cámara de vacío puede ser controlada rápidamente y con precisión. Para la alta presión (como la presión de aproximadamente 1 atmósfera), el modo de control aguas abajo puede controlar eficazmente la velocidad de bombeo de la bomba de vacío, de modo que la presión en la cámara de vacío puede ser controlada de forma rápida y precisa. Al mismo tiempo, se puede evitar el gas de muestra y otros trabajos en la entrada de aire. Utilizando la válvula de aguja electrónica de la serie FC, el nivel de vacío dentro de la cámara puede ser modulado con alta resolución. Si hay regulaciones estrictas sobre el flujo de aire de entrada y la presión de la cavidad, deben ser controlados con precisión y es necesario adoptar el modo de control de dos vías. El modo de control bidireccional puede controlar diferentes flujos de aire de admisión bajo una presión constante, pero el modo de control bidireccional requiere que el controlador tenga una función de control bidireccional, lo que plantea mayores requisitos de capacidad para el controlador. Las características de los tres modos de control anteriores se presentan en detalle. (2) Modo de control de la temperatura Además, el modo de medición y control de la temperatura debe seleccionarse en función de los diferentes rangos de temperatura y de los requisitos de precisión del control de la temperatura. Por ejemplo, cuando la temperatura está cerca de la temperatura ambiente y la precisión del control de la temperatura es alta. Se requiere un modo de control bidireccional con funciones de calefacción y refrigeración. Sólo este modo para garantizar una precisión de control de temperatura suficientemente alta. Si se trata de un rango de temperatura alto, también se recomienda utilizar un método de control bidireccional, es decir, centrarse en la calefacción y suministrar una cierta compensación de refrigeración para mejorar la precisión del control de la temperatura y la estabilidad de la temperatura rápida. 2.2 Cómo elegir el sensor La precisión del sensor es la clave para garantizar la precisión de la medición y el control de la presión y la temperatura, por lo que la selección del sensor es especialmente importante. Para el control de la presión en el rango anterior, se recomienda encarecidamente utilizar el vacuómetro de condensador de película fina con la mayor precisión. La precisión de medición de este vacuómetro puede alcanzar 0,2% de su lectura, y tiene una buena linealidad en todo el rango, lo que es muy fácil de conectar. El controlador realiza un control lineal con alta resolución y pequeña deriva de temperatura. En la selección real, es necesario seleccionar un vacuómetro con un rango adecuado según los diferentes rangos de presión. Para el rango de presión antes mencionado de 0,1~300kPa, se pueden seleccionar dos tipos de vacuómetros, de 2 Torr y de 1000 Torr, para lograr una cobertura precisa del rango de presión. Para el control de la temperatura, cuando la temperatura no es alta, se recomienda encarecidamente el sensor de temperatura de termistor con la mayor precisión de medición. También se recomienda el termistor de alta temperatura o el sensor de temperatura de resistencia de platino para temperaturas más altas. Si la temperatura de calentamiento excede el rango de uso del termistor y del sensor de resistencia de platino, se recomienda utilizar un sensor de temperatura tipo termopar. Estos sensores de temperatura requieren una calibración antes de su uso. 2.3 Cómo elegir el actuador El actuador de control de presión es la clave para determinar si se puede lograr un control constante de alta estabilidad. Como se muestra en la Figura 2-2, se recomienda encarecidamente utilizar una válvula de aguja electrónica accionada por un motor paso a paso con pequeña linealidad e histéresis, y no se recomienda utilizar una válvula de solenoide proporcional con gran histéresis y error de control. La válvula de aguja electrónica puede disponerse en la entrada de aire y en la salida de gas, o puede disponerse una válvula de aguja electrónica según la selección del modo de control aguas arriba o aguas abajo. Si la cámara de vacío del espectrómetro es grande, la válvula de aguja electrónica debe ser sustituida por una válvula controlada electrónicamente con mayor diámetro y velocidad de flujo para lograr un control de presión constante más rápido. Visite https://www.genndih.com/proportional-flow-control-valve.htm Se recomienda utilizar una lámina termoeléctrica semiconductora con efecto Peltier para el actuador de control de temperatura. Esta lámina termoeléctrica tiene un modo de trabajo bidireccional de calentamiento y enfriamiento. Con un termistor y un controlador de alta precisión, se puede lograr un control de temperatura de muy alta precisión, lo cual es muy adecuado para espectrómetros con control de temperatura de cámaras de trabajo pequeñas. Si la cámara de trabajo del espectrómetro es grande y la temperatura es inferior a 300 °C, se recomienda utilizar un baño de circulación de escape externo con función de calentamiento y enfriamiento para la calefacción. Este baño de circulación también tiene función de calentamiento y enfriamiento y puede lograr una alta precisión en el control de la temperatura. Si el espectrómetro trabaja a una temperatura más alta, se recomienda utilizar un método de calentamiento por hilo de resistencia o por luz, y al mismo tiempo, se equipa con un cierto dispositivo de ventilación y enfriamiento para mejorar la velocidad de respuesta del calentamiento, asegurando así la estabilidad y la velocidad del control de la temperatura. 2.4 Cómo elegir el controlador El controlador es la última garantía para conseguir una medición y control de la presión y la temperatura de alta precisión y estabilidad. En el diseño del control de la presión, el controlador debe ser seleccionado de acuerdo con el manómetro y el actuador elegidos. Para la introducción detallada de la selección, por favor refiérase a la literatura [10]. De acuerdo con los cálculos de la literatura, si se quiere garantizar la precisión de la medición y el control de la presión, se debe utilizar un número de colector digital con al menos 16 bits. Del mismo modo, la precisión de la medición y el control de la temperatura también está determinada por el número de colectores digitales. Por lo tanto, para el control de la presión y la temperatura en el espectrómetro, se recomienda utilizar el controlador de adquisición A/D de 24 bits desarrollado por KaoLu con la mayor precisión y rentabilidad, y combinado con la función de control de parámetros PID. De acuerdo con la selección anterior, el esquema final de medición y control de presión y temperatura se muestra en la Figura 2-3. En particular, cabe destacar que el control de presión y temperatura mencionado anteriormente adopta básicamente un modo de control bidireccional. Este controlador de alta precisión desarrollado por nosotros tiene esta función. Además, en la aplicación práctica del espectrómetro, la presión y la temperatura deben ser controladas al mismo tiempo. Se pueden utilizar dos controladores que controlen la válvula de aguja electrónica respectivamente, pero el volumen total del espectrómetro correspondiente aumenta, el funcionamiento se complica y el coste se incrementa. En la actualidad, el controlador de alta precisión recomendado es un controlador PID de doble canal. Dos canales pueden controlar independientemente diferentes parámetros PID y realizar el autoajuste de los parámetros PID al mismo tiempo, y cada canal tiene una función de control bidireccional. Simplifica eficazmente el controlador y reduce el tamaño y el coste del instrumento. 3. Conclusión En resumen, mediante el análisis de los requisitos de medición y control de la presión y la temperatura del espectrómetro, se determina el esquema técnico detallado de medición y control de la temperatura y la presión. La base para la determinación del esquema y los parámetros técnicos de los correspondientes componentes seleccionados se presentan en detalle. El uso de la válvula de aguja electrónica de la serie FC en una modulación de bucle cerrado permite al usuario controlar el nivel de presión con gran precisión. Toda la solución técnica puede satisfacer plenamente los requisitos de medición y control de presión y temperatura del espectrómetro, y tiene las características de alta precisión de medición y control, potentes funciones, amplio rango de aplicación, fácil integración y bajo coste. Salvo el vacuómetro de condensador de película fina, que es un producto importado (el vacuómetro localizado también es opcional), todos los componentes e instrumentos seleccionados en el esquema son de fabricación taiwanesa.

Control preciso de la presión en la fusión de lechos de polvo por láser al vacío Proceso de fusión SLM de baja presión en la fusión del lecho de polvo por láser Características: El baño de fusión es más estable y reduce la porosidad. Requisitos de la atmósfera de baja presión: Se alcanza un control rápido y preciso de la presión del aire dentro de la ventana de proceso de 5kPa~101kPa. Control de la presión Método de control: método de control de dos vías, ajustando la entrada de aire aguas arriba usando la válvula electrónica de control de flujo de aire y la válvula secundaria de control de flujo proporcional aguas abajo al mismo tiempo. También puede ajustar el flujo de entrada de aire y la tasa de escape de la bomba de vacío. Esto materializará un control del nivel de vacío de alta precisión en la fusión del lecho de polvo láser. Para más información sobre la válvula electrónica de control de flujo de aire, visite https://www.genndih.com/proportional-flow-control-valve.htm Sensor: sensor de presión de vacío, el rango de medición es de 5kPa~101kPa, y la precisión es de ±0,2%. Controlador: controlador PID de dos vías, función de control de dos vías

Aplicación de la Válvula Reguladora Eléctrica Resistente a la Corrosión: Control automático del flujo de ácido fosfórico en el proceso de clarificación de sulfito de sacarosa Resumen: En la actualidad, la válvula reguladora se utiliza generalmente para controlar el caudal de ácido fosfórico líquido en el proceso de clarificación de sulfito de sacarosa. Por lo tanto, la válvula reguladora generalmente tiene el problema de una pobre resistencia a la corrosión, un tiempo de respuesta lento y un bajo nivel automático. Este artículo presenta un nuevo tipo de válvula de regulación electrónica resistente a la corrosión basada en la válvula de aguja, que adopta la propulsión del motor de pasos y la tecnología de sellado de caucho de perfluoroéter FFKM. Tiene un buen rendimiento de sellado y una velocidad de respuesta de microsegundos que puede utilizarse en vacío. Puede ser accionada directamente por una señal de voltaje DC o RS 485, y ha sido utilizada en líneas de producción de sacarosa. 1. Preguntas En el proceso actual de producción de sacarosa, se utiliza generalmente el proceso de clarificación con sulfito, y el sistema de control automático del ácido fosfórico requiere la dosificación automática del ácido fosfórico. De acuerdo con el flujo de jugo de caña, la dosificación de ácido fosfórico se ajusta de forma continua y automática en tiempo real para garantizar la precisión de la adición de ácido fosfórico. La cantidad de adición de ácido fosfórico se controla ajustando el caudal del líquido de ácido fosfórico con una concentración de 85%, pero existen los siguientes problemas que deben resolverse urgentemente: (1) Poca resistencia a la corrosión: La solución de ácido fosfórico con una concentración de 85% es un tipo de ácido inorgánico medio-fuerte, que tiene cierta corrosividad. En la actualidad, la resistencia a la corrosión de la mayoría de las válvulas eléctricas de control de flujo es generalmente pobre y no se puede utilizar para la regulación del flujo de ácido sulfúrico. (2) Bajo nivel de automatización: En la actualidad, la mayor parte de la regulación del flujo de ácido fosfórico sigue utilizando válvulas de control manuales resistentes a la corrosión. La escasa precisión y puntualidad de la adición de ácido fosfórico afecta a la calidad del producto, y es imposible dominar con precisión el uso del ácido fosfórico. (3) Poca precisión y lenta velocidad de respuesta: Aunque también hay válvulas de bola eléctricas/neumáticas y válvulas de mariposa para la regulación del flujo, pero generalmente el diámetro es demasiado grande, la precisión de la regulación es pobre, y la velocidad de respuesta es lenta, lo que no puede cumplir con los requisitos de precisión de regulación del nivel de ppm del flujo de ácido fosfórico. 2. Válvula de regulación eléctrica de precisión resistente a la corrosión La válvula de aguja electrónica resistente a la corrosión desarrollada por KaoLu es una válvula de aguja de medición electrónica inteligente de dos vías, que utiliza un motor lineal de pasos de alta precisión para accionar el eje de la válvula. Los principales indicadores técnicos son los siguientes (1) Material de contacto: acero inoxidable (2) Material de sellado: caucho de perfluoroéter (FFKM) (3) Tiempo de respuesta: 0,8s (desde el cierre total hasta la apertura total) (4) Fluido: gas y líquido (5) Rango de presión: -1~7bar (6) Diámetro interior del acelerador de carrete: 0,9~4,1mm (7) Rango de flujo: 0,1~2000L/m (8) Linealidad: ±0.1~±11% (9) Repetibilidad: ±0,1% (escala completa) (10) Rango de temperatura de funcionamiento: 0~84 (11) Señal de control: 0~10VDC o RS485 (12) Alimentación de trabajo: 24V (≤12W) Para más información sobre el producto, visite https://www.genndih.com/proportional-flow-control-valve.htm