Application of Electric Corrosion-Resistant Regulating Valve: Automatic Control of Phosphoric Acid Flow in Sucrose Sulfite Clarification Process Abstract: At present, regulating valve is generally used to control the flow rate of liquid phosphoric acid in sucrose sulfite clarification process. Thus, regulating valve generally has problem of poor corrosion resistance, slow response time and low automatic level. This article introduces a new type of corrosion-resistant electronic control valve based on needle valve, which adopts stepper motor propulsion and FFKM perfluoroether rubber sealing technology. It has good sealing performance and microsecond response speed that can be used in vacuum. It can be directly driven by a DC voltage signal or RS 485, and has been used in sucrose production lines. 1. Questions In the current sucrose production process, the sulfite clarification process is generally used, and the phosphoric acid automatic control system requires the automatic proportioning of phosphoric acid. According to the flow of cane juice, the dosage of phosphoric acid is continuously and automatically adjusted in real time to ensure the accuracy of phosphoric acid addition. The phosphoric acid addition amount is controlled by adjusting flow rate of phosphoric acid liquid with a concentration of 85%, but there are the following problems that need to be solved urgently: (1) Poor corrosion resistance: Phosphoric acid solution with a concentration of 85% is a kind of inorganic medium-strong acid, which has certain corrosiveness. At present, the corrosion resistance of most electric flow control valves is generally poor and cannot be used for sulfuric acid flow regulation. (2) Low level of automation: At present, most of the phosphoric acid flow regulation still uses corrosion-resistant manual control valves. The poor accuracy and timeliness of phosphoric acid addition affects product quality, and it is impossible to accurately master the use of phosphoric acid. (3) Poor accuracy and slow response speed: Although there are also electric/pneumatic ball valves and butterfly valves for flow regulation, but generally the diameter is too large, the regulation precision is poor, and the response speed is slow, which cannot meet the ppm level regulation accuracy requirements of phosphoric acid flow. 2. Corrosion-resistant precision electric regulating valve The corrosion-resistant electronic needle valve developed by KaoLu is a smart electronic two-way metering needle valve, which uses a high-precision linear stepper motor to drive the valve shaft. The main technical indicators are as follows: (1) Contact material: stainless steel (2) Sealing material: perfluoroether rubber (FFKM) (3) Response time: 0.8s (fully closure to fully opening) (4) Fluid: gas and liquid (5) Pressure range: -1~7bar (6) Spool throttle inner diameter: 0.9~4.1mm (7) Flow range: 0.1~2000L/m (8) Linearity: ±0.1~±11% (9) Repeatability: ±0.1% (full scale) (10) Operating temperature range: 0~84 (11) Control signal: 0~10VDC or RS485 (12) Working power supply: 24V (≤12W) For further product information, please visit https://www.genndih.com/proportional-flow-control-valve.htm

Precise Pressure Control in Vacuum Laser Powder Bed Fusion Low pressure SLM fusion process in laser powder bed fusion Features: The molten pool is more stable and reduces porosity. Low-pressure atmosphere requirements: Fast and accurate air pressure control is reached within the process window of 5kPa~101kPa. Pressure Control Control method: two-way control method, adjusting upstream air intake using electronic air flow control valve and downstream secondary proportional flow contro valve at the same time. It can also adjust the air intake flow and vacuum pump exhaust rate. This will materialise an high accuracy vacuum level control in laser powder bed fusion. For further information on electronic air flow control valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm Sensor: vacuum pressure sensor, the measurement range is 5kPa~101kPa, and the accuracy is ±0.2%. Controller: two-way PID controller, two-way control function

Abstract: Spectral measurement and spectrometer are important technical measures in detection and monitoring. In order to obtain satisfied measurement accuracy, spectrometer requires high-precision pressure and temperature transducers, actuators and PID controllers, and needs to have the features of a wide range of applications, high precision, easy integration and low cost. This article will focus the characteristics of spectrometer pressure and temperature control, combined with the innovative products of KaoLu FC series electronic needle valve. Also gives a high-precision and low cost high performance spectrum measurement, spectrometer temperature and pressure measurement and control program. 1. The formulation of the question As a qualitative and quantitative scientific analysis method, spectral measurement has become an important technical measure in various detection and monitoring research due to its advantages of high measurement accuracy and fast response speed. However, in practical applications, the pressure and temperature changes of the sample gas will affect the measurement results. The following are some of the research work done at home and abroad on the temperature and pressure control in the spectral measurement and the characteristics of the impact: ①. Pressure control range Different spectrometers and spectrometers have different requirements for the pressure control range. For example, the infrared spectroscopy which uses gas curette, the intensity of the absorption peak can be achieved by adjusting the pressure of the sample gas. The general pressure range is 0.5 ~ 60kPa. When using tunable diode laser absorption spectroscopy (TDLAS) technology to measure carbon dioxide concentration in the atmosphere, a stable pressure in the range of 6~101kPa is required. In the precise control of the pressure inside the detector of the X-ray spectrometer, the density of the working gas should be stabilized to ensure the measurement accuracy of the detector. Generally, the pressure should be controlled at around one atmospheric pressure or higher, while the working pressure of the laser-induced breakdown spectrometer should be Up to 275kPa. It can be seen that the pressure control range of the working gas in the spectrometer is relatively wide, generally in the range of 0.1~300kPa, which basically covers the pressure range of 4 orders of magnitude from vacuum negative pressure to 3 times atmospheric pressure. ②. Pressure control accuracy In the test of spectral, the relationship between the observed spectral line intensity and the real gas density depends on the pressure of the gas sample, so the pressure control accuracy directly determines the spectral measurement accuracy. For example, the pressure control accuracy in the spectrum analyzer of Picarro Company is ±0.0005 atmosphere (fluctuation rate ±0.05%@1 atmosphere pressure). Literature [1] reported that the absorption tank was controlled when the set pressure was 6.67kPa. After four hours of continuous control, the pressure fluctuation was ±3.2Pa, and the fluctuation rate was ±0.047%. Literature [2] reported that when gas pressure in a sample cell was also controlled at 6.67kPa, the long-term fluctuation range of the pressure was 7Pa, and the fluctuation rate was ±0.047%. Literature [3] reported the stability measurement of the laser infrared multi-pass cell pressure control system. The target pressure was set to 60 Torr, the maximum fluctuation was ±0.04 Torr within 150~200s, and the fluctuation rate was ±0.067%. Literature [4] specially reported the design and research of the high-precision temperature and pressure control system of the spectroscopic measuring instrument. The target pressure value is 18.665kPa, the constant pressure control for 42 hours, the maximum deviation is 5.33Pa, and the fluctuation rate is ±0.014%. Literature [5] introduced the results of constant pressure control of the detector in the X-ray spectrometer. During the constant pressure of the working gas at 940 hPa, the fluctuation was less than ± 2 hPa, and the fluctuation rate was ± 2%. Literature [6] introduced the constant pressure control technology of X-ray photoelectric spectrometer in the pressure range of 0.05~30mbar. When the set value is 0.1mbar, the constant accuracy can reach ±0.001mbar, and the fluctuation rate is ±1%. ③. Temperature control accuracy In the test of spectral, the relationship between spectral line intensity and true gas density also depends on the temperature stability of the gas sample. The stability of temperature would also affect the stability of pressure. Literature [2] reported that the gas temperature in the sample cell was controlled at room temperature (24°C), the short-term temperature fluctuation is ±0.01°C, the long-term temperature drift is ±0.025°C, and the fluctuation rate is ±0.1%. Literature [4] reported that high-precision temperature control system of the spectrometer, the temperature is controlled at 45°C, and the temperature fluctuation within 42 hours is ±0.0015°C, and the fluctuation rate is less than ±0.004%. To sum up, the pressure and temperature changes of the sample gas are the main factors affecting the measurement results. So that in the spectral measurement and various spectrometers, the pressure, temperature adjustment and control of the sample gas has the following requirements: (1) The pressure control range is very wide (0.1~300kPa), but the corresponding measurement and control accuracy is really high, which make high demands on pressure measurement sensors, control valves, vacuum pumps and corresponding controllers. These four components in this closed-loop control system must match each other; otherwise it is difficult to obtain satisfied results. (2) Similarly in the process of high-precision temperature control, appropriate temperature sensors, heating devices, power supply and controller. These four components in the temperature closed-loop control system must also match each other. (3) High-precision controllers would be used in the two closed-loop control systems of pressure and temperature. In order to reduce experimental cost and cost of spectrometer, we want to use a high-precision controller with 2 simultaneous PID automatic control functions. (4) Focusing on different spectral measurements and spectrometers, their test structures are not the same, which requires the independence of each component in the temperature and pressure control system. In this way, it is beneficial to the integration of the test device and spectrometer.  Overall, in order to obtain the satisfied accuracy of spectral measurement, high-precision pressure and temperature sensors and actuators are required.It has the characteristics of wide application range, high precision, easy integration and low cost. This article will focus on these features, combine with the innovative products of KaoLu and provide high-precision and cost-effective spectral measurement and spectrometer temperature and pressure measurement and control plan. 2. Spectrometer pressure and temperature integrated measurement and control method 2.1 Control mode design (1) Pressure Control Mode As mentioned before, for control range of the spectrometer (0.1~300kPa), the best solution is to select the corresponding measurement and control mode according to the specific pressure range used. As shown in Figure 2-1, it is recommended to use the upstream control mode for the low pressure range. For the high pressure range, the downstream measurement and control mode is adopted; it can also adopt the two-way control mode of simultaneous upstream and downstream control. Figure2-1 Three mode of pressure control The upstream control mode is adopted for low pressure, which can repeatedly exert the pumping speed of the vacuum pump, so that the pressure in the vacuum chamber can be quickly and accurately controlled. For high pressure (such as about 1 atmosphere pressure), the downstream control mode can effectively control the pumping speed of the vacuum pump, so that the pressure in the vacuum chamber can be controlled quickly and accurately. At the same time, the sample gas and other work at the air inlet can be avoided. Using FC series electronic needle valve, the vacuum level inside the chamber can be modulated with high resolution. If there are strict regulations on intake air flow and cavity pressure, they need to be accurately controlled and two-way control mode needs to be adopted. Two-way control mode can control different intake air flows under a constant pressure, but the two-way control mode requires the controller to have two-way control function, which puts forward higher capacity requirements for the controller. The characteristics of the above three control modes are introduced in detail. (2) Temperature control mode Also, the temperature measurement and control mode should be selected according to different temperature ranges and temperature control accuracy requirements. For example, when the temperature is near room temperature and the temperature control accuracy is high. It required a two-way control mode with heating and cooling functions. Only this mode to ensure a sufficiently high temperature control accuracy. If it is around the high temperature range, it is also recommended to use a two-way control method, that is, to focus on heating and supply a certain cooling compensation to improve the temperature control accuracy and rapid temperature stability. 2.2 How to choose sensor The accuracy of sensor is the key to ensure the accuracy of pressure and temperature measurement and control, so selection of sensor is particularly important. For pressure control in the above range, it is strongly recommended to use the thin-film capacitor vacuum gauge with the highest accuracy. The measurement accuracy of this vacuum gauge can reach 0.2% of its reading, and it has good linearity in the full range, which is very easy to connect. The controller performs linear control with high resolution and small temperature drift. In the actual selection, it is necessary to select a vacuum gauge with a suitable range according to different pressure ranges. For the above-mentioned pressure range of 0.1~300kPa, two types of vacuum gauges, 2 Torr and 1000 Torr, can be selected to achieve accurate pressure range cover. For temperature control, when temperature is not high, thermistor temperature sensor with the highest measurement accuracy is strongly recommended. High temperature thermistor or platinum resistance temperature sensor is also recommended for higher temperatures. If heating temperature exceeds the use range of thermistor and platinum resistance sensor, it is recommended to use a thermocouple type temperature sensor. These temperature sensors require calibration before using. 2.3 How to choose actuator The pressure control actuator is the key to determine whether high stability constant control can be achieved. As shown in Figure 2-2, it is strongly recommended to use an electronic needle valve driven by a stepper motor with small linearity and hysteresis, and it is not recommended to use a proportional solenoid valve with large hysteresis and control error. Electronic needle valve can be arranged at air intake and gas outlet, or an electronic needle valve can be arranged according to the selection of upstream or downstream control mode. If the vacuum chamber of the spectrometer is large, electronic needle valve needs to be replaced with an electronically controlled valve with larger diameter and flow rate so as to achieve constant pressure control faster. Please visit https://www.genndih.com/proportional-flow-control-valve.htm It is recommended to use a semiconductor thermoelectric sheet with Peltier effect for the temperature control actuator. This thermoelectric sheet has a two-way working mode of heating and cooling. With a high-precision thermistor and controller, ultra-high-precision temperature control can be achieved, which is very suitable for spectrometers with temperature control of small working chambers. If working chamber of spectrometer is large and temperature is below 300 °C, it is recommended to use an external exhaust circulating bath with heating and cooling function for heating. This circulating bath also has heating and cooling function and can achieve high temperature control accuracy. If the spectrometer works at a higher temperature, it is recommended to use a resistance wire or light heating method, and at the same time, it equipped with a certain ventilation and cooling device to improve response speed of heating, thereby ensuring the stability and speed of temperature control. 2.4 How to choose controller The controller is the last guarantee to achieve high-precision and high-stability pressure and temperature measurement and control. In pressure control design, controller needs to be selected according to the chosen vacuum gauge and actuator. For the detailed introduction of selection, please refer to the literature [10]. According to the calculation of literature, if the accuracy of pressure measurement and control is to be ensured, a number of digital collector with at least 16 bits must be used. Similarly, the accuracy of temperature measurement and control is also determined by the number of digital collector. Therefore, for the control of pressure and temperature in the spectrometer, it is recommended to use the 24-bit A/D acquisition controller developed by KaoLu with the highest accuracy and cost-effectiveness, and combined with the PID parameter control function. According to the above selection, the final pressure and temperature measurement and control scheme is shown in Figure 2-3. In particular, it should be pointed out that the above-mentioned pressure and temperature control basically adopts a two-way control mode. This high-precision controller developed by us has this function. In addition, in practical application of spectrometer, pressure and temperature need to be controlled at the same time. Two controllers controlling electronic needle valve can be used respectively, but overall volume of corresponding spectrometer increases, operation becomes complicated and cost is increased. Now recommended high-precision controller is a dual-channel PID controller. Two channels can independently control different PID parameters and perform auto-tuning of PID parameters at the same time, and each channel has a two-way control function. It effectively simplifies the controller and reduces instrument size and cost. 3. Conclusion To sum up, through the analysis of pressure and temperature measurement and control requirements of spectrometer, the detailed temperature and pressure measurement and control technical scheme is determined. The basis for determination of scheme and technical parameters of the corresponding selected components are introduced in detail. Using FC series electronic needle valve in a closed loop modulation allows user to control pressure level in high precision. The whole technical solution can fully meet the requirements of spectrum measurement and spectrometer for pressure and temperature measurement and control, and has the characteristics of high measurement and control accuracy, powerful functions, wide application range, easy integration and low cost. Except the thin-film capacitor vacuum gauge is an imported product (localized vacuum gauge is also optional), all the selected components and instruments in the scheme are made in Taiwan.

Abstract: Focusing on high-precision control of low-temperature medium in cryostat, this article mainly introduces decompression and temperature-control method of low-temperature medium and the influence of air pressure control accuracy on the low-temperature stability. Three modes of heating, flow control and pressure control, as well as corresponding specific working conditions that incorporate electric pneumatic flow control valve and details. 1. Introduction In cryostat, the main reason for temperature fluctuation of cryogenic medium (liquid helium and liquid nitrogen, etc.) is the change of pressure (vacuum) at the top of boiling cryogenic medium. Therefore, in order to reach stable temperature inside cryogenic medium, it is necessary to accurately control air pressure at the top of cryogenic medium. The international and localized temperature control of cryostats mostly adopts the following three technical approaches: (1) Active control method: The heating circuit directly leads into vacuum chamber immersed in the low-temperature medium, and temperature real-time monitoring data of vacuum chamber is used to compare with target temperature value and then control the current added to heating circuit. (2) Passive control method: Control air pressure at the top of low temperature medium to stabilize temperature of low temperature medium. (3) Composite control method: The above two control methods are combined, and heating control circuit directly lead into vacuum chamber immersed in the low temperature medium, and air pressure above the low temperature medium is also controlled at the same time. The resistance heating temperature control method is already a very mature technology. This article will mainly focus on pressure control method at the top of low temperature medium, and introduce the influence of pressure control accuracy on the low temperature stability, as well as the realization method and specific scheme of high precision pressure control. 2. The relationship between air pressure control accuracy and temperature stability Taking liquid hydrogen as an example, saturated vapor pressure of liquid hydrogen and the corresponding temperature change curve are shown in Figure 1. As can be seen in Figure 1, in a very small temperature range, the above curve can be described by a straight line, so it can be obtained in temperature range of about 4K; fluctuation of air pressure about 100Pa can cause a temperature fluctuation of about 1mK. Therefore, it can be considered that if fluctuation of less than 1mK is to be reached, fluctuation of air pressure cannot exceed 100Pa. 3. Three modes of top air pressure control There are generally three modes of air pressure control at the top of the cryogenic medium: resistance heating, flow control and pressure control. 3.1 Resistance heating mode In constant temperature control process of cryostat, the resistance heating mode is to place a resistance wire heater in low temperature medium. As shown in Figure 2, vacuum gauge detects the change of air pressure at the top, and PID controller changes heating current to adjust and control top air pressure, keep the top air pressure constant at set value. It can be seen from Figure 2 that resistance heating mode is more suitable for increasing temperature control method of increasing pressure at the top, but it cannot reduce pressure and cooling. 3.2 Flow Control Mode Flow control mode is a typical reducing pressure and cooling mode. As shown in Figure 3, vacuum pump continuously extracts cryostat at a certain pumping speed to reduce the top air pressure. The vacuum gauge, electronic pneumatic flow control valve and PID controller form a closed-loop control loop. The FC series electronic pneumatic flow control valve adjusts air flow to keep the top air pressure accurately and constant at vacuum degree. It can be seen that the flow control mode is more suitable for cooling and temperature control method of reducing the top air pressure, but it cannot reach supercharging and heating. In addition, in flow control mode, the continuous pumping of vacuum pump makes ineffective dissipation of the low temperature medium more serious. For further information on FC series electronic pneumatic flow control valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm 3.3 Pressure Control Mode Pressure control mode is a temperature control mode that can increase or decrease pressure. As shown in Figure 4, when adopting vacuum pump to evacuate is the mode of reducing pressure. When adopting booster pump is the mode of increasing pressure. So that it can reach continuous temperature control in a wide temperature area. The used proportional pressure regulator comes with one air inlet (atmospheric pressure). Combined with vacuum pump, it can effectively avoid a large amount of ineffective dissipation of low temperature medium while controlling the top pressure at a constant pressure. In addition, the supercharging method here can also be reached by adding an electric heater to the low temperature medium. 4. Additional Working Details During implementation of the above three control modes, it should specifically notice to the following details: (1) Selection of vacuum gauge Vacuum gauge is a sensor that measures change in air pressure at the top. The key to determining the stability of temperature control of cryostat, so be sure to choose a high-precision vacuum gauge. At present, high-precision vacuum gauges are generally capacitive film gauges, and the general overall accuracy is 0.2%. As mentioned above, in constant temperature control process of liquid hydrogen around 4K, air pressure fluctuation is required not to exceed 100Pa, and ±50Pa. If it corresponds to air pressure control of 100kPa, the accuracy of vacuum gauge needs to be higher than ±0.05%. It can be seen that constant temperature control with temperature fluctuation less than 1mK, a higher precision vacuum gauge is also required. (2) Selection of PID controller In the process of constant temperature control, PID controller collects measured value of vacuum gauge through A/D converter, and then sends control signal to actuator (electric needle valve, pressure regulator and heating power supply, etc.) through the D/A converter after calculation. ). For this reason, to ensure that high precision and control accuracy of vacuum gauge can be fully utilized and regulated with an electronic pneumatic flow control valve, the higher the precision of A/D and D/A converters, the better at least 16 bit, and a 24-bit high-precision PID controller is strongly recommended. (3) Allocation of voltage regulator Pressure regulator is a pressure control device that integrates a vacuum pressure sensor, a controller and a valve, but the accuracy of vacuum pressure sensor is far less than thin-film capacitor, and the accuracy of controller is also relatively low. Thus, when using a voltage regulator, an external control mode should be selected, that is, a thin-film capacitor is used as a control sensor. In addition, it should be noted that A/D and D/A converters of controller in regulator have low precision. Thus, for high-precision and high-stability top air pressure control, pressure control mode is not recommended unless a specially made high-precision voltage regulator is used.

Localized Substitution of INFICON VDE016 and Pfeiffer EVR116 Gas Control Valves and PID Controllers Abstract: Not only comparing to VDE 016 of INFICON and EVR 116 gas control valve of Pfeiffer but VCC500 of INFICON and RVC 300 controller of Pfeiffer. This article introduces the corresponding localized alternative products electronic air flow control valve and multi-function of high-precision PID controller. Also introduces the corresponding features and technical indicators of localized alternative products. 1. Overview The gas control valve of INFICON ‘s VDE 016 and Pfeiffer’s EVR 116 is actually the exact same control valve, only the OEM is different. As shown in Figure 1, this gas control valve is a needle valve driven by a stepper motor, which can convert an external control signal into a prescribed valve needle position, thereby adjusting the opening of the valve to reach gas flow control. The external control signal can be in the following three types : (1) DC simulation voltage (0~10VDC) (2) Interface module (3) RS232 interface For this gas control valve, INFICON and Pfeiffer provided matching controllers, as shown in Figure 2, the models are: INFICON: VCC500-Z; Pfeiffer: RVC 300. This article will introduce the corresponding technical indicators for the above-mentioned control valves and controllers, and introduce the corresponding localized alternative products and their technical indicators, so as to provide cost-effective products for localized substitution. 2. Technical indicators of foreign products 2.1 Specifications of gas control valve The performance parametersof INFICON and Pfeiffer’s control valves are shown in Table 1, and the technical indicators are shown in Table 2. 2.2 Controller Technical Indicators The technical indicators of controller performance of INFICON and Pfeiffer are shown in Table 3. Operating Mode Pressure Control, Gas flow regulation Analog Output 4 channels: vacuum pressure sensor signal, valve signal(0-10VDC), valve position, +10VDC reference voltage(10mA) Number Output 8 channels: open valve, closed valve, valve position, valve error, sensor error, preparation, divergence, sensor condition Analog Input 2 channels: vacuum pressure set point (standard value),flow set point (standard value) Number Input 8 channels: flow reduction, flow addition, external closure, external open, flow mode, pressure mode, discharge open, exhausting open Characteristic After power outage, turn on output “reach the standard value”, then it can adjust tolerance Display Unit mbar, Pa, Torr, mV Language English, German Communication Interface RS232C, RS485   Controller type PI automatic: it can choose control speed step 1-99 PID: Users can define parameters Control Accuracy ±5% FS sensor Display Accuracy ±0.2% FS sensor Power Supply Voltage90 ~250VAC Weight 1.65kg From the above-mentioned controller technical indicators and practical application experience, it can be found that INFICON and Pfeiffer controllers have the following deficiencies: (1) Single-channel measurement and control: that is, only one vacuum gauge signal and one control valve can be collected. Although there are multiple analog and digital input and output channels, only one closed-loop control can be performed. This single channel controller will not be able to cover the wide range that requires two vacuum gauges to cover. (2) No PID self-regulating function: The biggest disadvantage of INFICON and Pfeiffer controllers is the lack of PID parameter self-tuning function, which brings inconvenience in practical applications, requiring users to find suitable PID parameters by themselves. Sometimes the optimal PID parameters cannot be obtained in the end, which seriously affects the control effect. (3) Poor control accuracy: The control accuracy is ±5% of the full scale of sensor, which basically shows that acquisition and control circuit in the controller uses 12-bit A/D and D/A converters, which is the key to determining the control accuracy. 3. KaoLu’s electronic air flow control valve replaces INFICON and PFA control valves The control valve of INFICON and Pfeiffer is a typical electronic air flow control valve driven by stepper motor. The performance indicator is very superior. The only disadvantage is that the opening of needle valve is small, thus it causes a small flow. Moreover, the price is too expensive. In order to reach the replacement of gas flow control valve and improve the low cost high performance, KaoLu also used stepper motor in needle valve technology for localization, and developed a series of electronic air flow control valve with different flow rates. As shown in Figure 3, fully realized it has been replaced, and the price is only one-third of foreign products. The detailed technical indicators are shown in Figure 4. Please visit https://www.genndih.com/proportional-flow-control-valve.htm (Figure3 KaoLu’s FC electronic air flow control valve) 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 electronic air flow control valve) 3. Localized high-precision dual-channel PID controller replaces INFICON and PFA controllers In order to use the measurement accuracy of vacuum gauges fully (such as capacitive film pressure gauges), at least 16-bit analog-to-digital and digital-to-analog converters are required for data acquisition and control of controller. In recent years, KaoLu have developed the FC series of high-precision 24-bit general-purpose PID controllers, as shown in Figure 5. 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 realize the simultaneous measurement and control of temperature and pressure. (3) A variety of output parameters: 47 kinds of input signals (thermocouple, thermal resistance, DC voltage) can reach simultaneous test, display and control of different parameters. (4) Multi-function: forward, reverse, forward and reverse two-way control. (5) PID control: The improved PID algorithm supports PV differential and differential advance control. There are 20 groups of PIDs. (6) 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. (7) Program control: You can create and store up to 20 condensation programs by yourself, and you only need to select and call to start condensation (program control mode). In the vacuum degree control, downstream control mode is more suitable for vacuum degree close to atmospheric pressure, but upstream air intake control mode is required for vacuum degree control of less than 10mbar. Therefore, in order to satisfy the full control degree of vacuum, the dual sensor and two-way control mode as shown in Figure 6 can be used. In the control mode shown in Figure 6, it is necessary to use the forward and reverse control and dual sensor automatic switching functions of the above FC-20 series dual-channel controller, that is, during different air pressure control processes; the controller automatically switches the corresponding range. Vacuum gauge, and select the corresponding electronic air flow control valve for control.

A Detailed Tutorial on Vacuum Degree and Temperature Control Method in Glove Box Abstract: In order to reach powerful functions of glove box for two environmental variables of vacuum and temperature in glove box. This article focuses on integrated solution for accurate measurement and control of vacuum and temperature, and describes the upstream, downstream, bi-directional methods. Also introduces the specific application of switching control mode in different vacuum degree ranges, and demonstrates the new proportional flow control valve and 24-bit ultra-high-precision PID controller used in the control. 1. Questions Vacuum glove boxes are often used for readily oxidizable and deliquescent substances. Chemical reactions, material processing and performance testing that require manual operations in an anaerobic and anhydrous environment are very helpful. The core function of glove box is to provide a vacuum environment and easy to use, but in current practical applications most glove boxes only use anaerobic environment and manual operation functions of glove box, and do not give full capacity to the role of glove box. The more powerful application of glove box is also reflected in the following two aspects: (1) The vacuum glove box is a hermetic environmental box, and the ultimate vacuum degree can generally reach about 10Pa, so that vacuum degree in glove box can be controlled at any set point between 10Pa and atmospheric pressure as required. Various chemical reactions, experiments and tests that are sensitive to vacuum can be carried out; also various manual operations can be carried out without changing and destroying the vacuum environment. (2) In addition to vacuum, temperature is another important environmental variable for many reactions, experiments and tests. By placing the corresponding heating device in the glove box, various experimental studies under the combined environment of temperature and vacuum degree can be carried out. And so on, other physical quantity environmental conditions can also be configured to form multi-physical quantity coupling test conditions under various boundary conditions. In order to achieve the full performance of a vacuum glove box, it focuses on two environmental variables of vacuum degree and temperature in the glove box. This article introduces in detail the integrated solution for accurate measurement and control of vacuum degree and temperature, and introduces the different vacuum degree ranges of upstream, downstream and bidirectional control modes in vacuum control process. 2. Vacuum control in glove box Glove box belongs to a low vacuum environment cavity. The vacuum degree of the glove box using a mechanical pump can generally reach an absolute pressure of about 10Pa. By vacuuming and filling with inert gas, the vacuum degree of the glove box can be controlled from 10Pa to one atmosphere (absolute pressure 0.1MPa). For control in such a vacuum range spanning four orders of magnitude, vacuum sensors with different precisions will be used according to actual needs, and there will be different control modes accordingly. The following is the specific content of each control mode. 2.1 Upstream Control Mode As shown in Figure 1, under the condition that the pumping speeds of downstream vacuum pump is kept constant. The upstream control mode is to adjust the opening of proportional flow control valve of upstream air intake port through PID vacuum pressure controller according to the measurement signal of vacuum gauge, that is, by controlling intake flow to keep pressure in glove box at the set point. Upstream mode is often used for high vacuum control. 2.2 Downstream Control Mode As shown in Figure 2, under the condition that the pumping speed of downstream vacuum pump is kept constant, the downstream control mode is to adjust the opening of proportional flow control valve of downstream air outlet through PID vacuum pressure controller according to the measurement signal of vacuum gauge, that is, by controlling the air flow rate, the pressure in glove tank is controlled at the set value. We can see that downstream mode is often used for low vacuum control. 2.3 Bi-directional Control Mode The above upstream and downstream control modes have their own advantages, and are rarely used alone in practical applications. Generally, the upstream and downstream modes are integrated together, which is the so-called bi-directional control mode, as shown in Figure 3. In bi-directional control mode, the vacuum pressure controller is required to have forward and reverse control functions, that is, reverse control for upstream proportional flow control valve and reverse control for downstream proportional flow control valve. 2.4 Dual sensor automatic switching mode As mentioned above, if the accurate measurement and control of vacuum degree is carried out in the full range of 10Pa~0.1MPa, it is generally necessary to configure two high-precision diaphragm pressure gauges of 1000Torr and 10Torrswitch automatically. As shown in Figure 4, the high switching point (2-3) is the high point where low vacuum sensor works, and the low switching point (1-2) is the low point where high vacuum sensor works. The controller performs smoothing calculation between these two points. When the continuous sampling of low vacuum measurement PV1 and high vacuum measurement PV2 is below the lower switching point, switching to the rough vacuum sensor. When continuous sampling of low vacuum measured value PV1 and high vacuum measured value PV2 is above the upper switching point, the switch to high vacuum sensor is made. 3. Selection of vacuum gauge, valve and controller 3.1 Selection of vacuum sensor Like other sensors, various vacuum sensors also have a certain measurement range and accuracy. The basic rule is that a sensor with a wide measurement range has poor accuracy; a sensor with high measurement accuracy has a narrower measurement range. For glove box, as shown in Figure 5, the used vacuum sensors generally have the following three categories: (1) Conventional vacuum gauge: Pirani vacuum gauge, the accuracy is ±(15~50)% of the full scale, but one vacuum gauge can cover the full scale. (2) High-precision vacuum gauge: diaphragm pressure gauge, the accuracy is ±2.5% of the full scale, if it covers the range of 10Pa~0.1MPa, two vacuum gauges of 1000Torr and 10Torr are generally required. (3) Ultra-high precision vacuum gauge: semiconductor vacuum gauge, the accuracy is ±0.05% of the full scale, and the effective range is 50Pa ~ 0.1MPa, which cannot cover higher vacuum. 3.2 Selection of electric valve In glove box of vacuum control, two types of valves are generally involved: one is an air intake valve that adjusts the flow at air intake, and the other is an exhaust valve that adjusts the exhaust flow. Air intake valves are mostly used for small flow regulation, so needle valves are generally selected. Exhaust valves are mostly used for vacuuming, so ball valves with larger diameters are generally required. Due to the automatic control, both needle valves and ball valves are required to be driven by DC voltage, DC current or digital signal (RS485) which is the so-called proportional flow control valve. Proportional flow control valve selects a small-sized stepper motor-driven proportional flow control valve, as shown in Figure 6. This proportional flow control valve has high response speed (within 1s) and linearity (within 1%). For FC series proportional flow control valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm 3.2 Selection of controller From the above various control modes of vacuum degree of glove box, it can be seen that control process of vacuum degree puts forward high requirements for the controller. As shown in Figure 7, the selected controller must meet the following criteria: (1) At least it is a PID controller, and has the function of PID parameter self-tuning. (2) The accuracy of vacuum gauge itself is high. In order to give full play to the measurement accuracy of vacuum gauge, PID controller that needs data acquisition and control must have high accuracy. It is recommended that controller should be 24-bit A/D acquisition and 16-bit D/A output. (3) At least 2 channels are required to achieve simultaneous measurement and control of temperature and vacuum degree, also to reduce installation space. (4) Multiple input signal access functions, which can directly connect the input signals of different types of sensors such as thermocouple, thermal resistance, DC voltage, etc., to achieve simultaneous testing, display and control of different parameters. (5) Forward and reverse control function to reach two-way control mode. (6) With dual sensor switching function, 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. (7) Program control function, you can create and save multiple control programs by yourself, and you only need to select and call to start (program control mode). (8) It has a communication interface to connect with computer, such as the RS485 interface of the standard MODBUS protocol. 4. Temperature control of the glove box In addition to providing a vacuum environment, the glove box can also put a heating device in the glove box to perform various experiments and tests at different temperatures, so it is necessary to introduce temperature control function into glove box application. Temperature control is a very mature and classic technology, which is generally realized by using a PID controller in combination with a temperature sensor. In order to reduce the cost and installation volume, a multi-channel PID controller is generally used to control temperature and vacuum degree at the same time. The controller communicates with a computer to display and store measurement control data and curves. The working temperature in glove box is generally not required to be too high, but if thermal protection and cooling are done well, the working temperature range above 1000°C can also be achieved. The temperature measurement sensor generally chooses a thermocouple. If the measurement accuracy is high, the thermal resistance and the thermistor temperature sensor can also be selected. These sensors can be directly connected to the above-mentioned high-precision PID controller. 5. Conclusion Through the introduction of above content, the various control methods of vacuum degree and temperature in glove box and the main sensors, proportional flow control valve and PID controllers involved are basically explained. In specific applications, partial improvements can be made to the specific structure and function of glove box, and the overall design, installation and integration of glove box can also be carried out according to actual requirements. Although this article only introduces the measurement and control of vacuum degree and temperature in glove box, these methods and specific implementation contents can also be extended and applied to the control of test parameters in other fields that are more sensitive to the atmosphere environment, such as low temperature, geometric quantity, optics and acoustics.