Question 1

What Is A Pinch Valve?

Accepted Answer

A pinch valve is a type of fluid control valve. It applies a pinching force to the outer surface of flexible tubing. While pinching it collapses and seals the tubing to control fluid flow or pressure.
The main body of a pinch valve is not in direct contact with the gas or the liquid, and only the inside of the tube will have direct contact with the liquid and gas fluid flowing through. Therefore, the pinch valve is not in direct contact with the fluid.

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Question 2

Gas Blending

Accepted Answer

Our QKL electronic proportional pressure regulator ( I/P converter) products help with gas blending applications that need repeatable pressure control. By controlling the pressure of each specific gas to a process, a tailored blend can be achieved. Here two QKL proportional pressure regulator ( I/P converter) are controlling the pressure of two types of media in a gas blending application. Our proportional pressure regulator can also work in tandem with the proportional flow control valve to stabilise the inlet air pressure, and thus stabilise the flow rate after the flow control valve.
We also provide proportional flow control valve in this application, which can directly replace those of Burkert or Festo.

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Question 3

The basic knowledge and common errors and solutions of  solenoid valve (1)

Accepted Answer

Solenoid valve is an industrial equipment controlled by electromagnetic, which
adjusts the direction, flow, speed and other parameters of the medium in the
industrial control system. Focusing on structural principle, classification,
characteristics, selection, maintenance, errors and solutions of solenoid valves to
discuss.

1. Structural principle of solenoid valve

(1. Valve body 2. Air inlet 3. Air outlet 4. Conductor 5.Plunger)
When the solenoid valve is not set on, the valve needle blocks the passage of valve body under the action of spring, and solenoid valve is in the cut-off state. When the coil is powered on, the coil generates a magnetic force. The valve core is lifted up against the spring force, the channel in valve is opened, and the solenoid valve is in a conducting state.

2. Solenoid valve classification
Local and international solenoid valves are divided into three categories in principle (like: direct-acting, step-by-step direct-acting, pilot-operated). They are divided into six branches from the difference in structure and material of valve disc and the difference in principle (direct-acting diaphragm structure, step-by-step diaphragm structure, pilot-operated diaphragm structure, direct-acting piston structure, step-by-step piston structure, pilot piston structure). We would introduce three aspects: introduction, principle and characteristics.

1. Direct acting solenoid valve

Introduction:
There are two types: normally closed and normally open. The normally closed type is in a closed state when the power is off. When the coil is energized, an electromagnetic force is generated, so that the moving iron core overcomes the spring force and the static iron core is attracted to directly open the valve, and the medium is in a path. When the coil is powered off, the electromagnetic force disappears, the moving iron core is reset under the action of spring force, the valve port is directly closed, and the medium is blocked. The structure is simple, the action is reliable, and it works normally under zero pressure difference and micro-vacuum. Normally open is just the opposite, such as a solenoid valve with a flow diameter smaller than φ6.

Principle:
When the normally closed type is energized, the electromagnetic coil generates electromagnetic force to lift the opening piece from the valve seat, and the valve opens. When the power is off, the electromagnetic force disappears, the spring presses the opening piece on valve seat, and valve opens. (Normally open is the opposite of this)
Features:
It can work normally in vacuum, negative pressure and zero pressure, but the diameter generally does not exceed 25mm.

2. Processing direct-acting solenoid valve

Introduction:
This kind of valve adopts the one-time opening valve and the second-time opening valve to connect together. The main valve and the pilot valve step by step make the electromagnetic force and pressure difference directly open the main valve port. When the coil is energized, electromagnetic force is generated to make the moving iron core and static iron core pull together, the pilot valve port is opened and pilot valve port is set on the main valve port, and the moving iron core and the main valve core are connected together. The pressure of cavity is unloaded through the pilot valve port, and the main valve core moves upward under the simultaneous action of pressure difference and the electromagnetic force, opening the main valve medium to flow. When coil is powered off, the electromagnetic force disappears. At this time, the moving iron core closes pilot valve hole under the action of its own weight and spring force. At this time, the medium enters the upper cavity of main spool in the balance hole, which increases pressure in the upper cavity. The main valve is closed under the action of spring return and pressure, and the medium is cut off. Reasonable structure, reliable action, and reliable operation under zero pressure difference, such as: ZQDF, ZS, 2W, etc.

Principle:
It is a combination of direct action and pilot type. When there is no pressure difference between the inlet and the outlet, after the power is turned on, the electromagnetic force directly lifts the pilot valve and the main valve closing member upwards in turn, and the valve opens. When the inlet and outlet reach the starting pressure difference, after the power is turned on, the electromagnetic force pilots the small valve, the pressure in the lower chamber of the main valve rises, and the pressure in the upper chamber drops, so that the main valve is pushed up by the pressure difference. When the power is off, the pilot valve uses a spring. The force or medium pressure pushes the closing member, moving downward, causing the valve to close.

Features:
It can also operate under zero pressure difference or vacuum and high pressure, but the power is large and it must be installed horizontally.

3. Indirect pilot solenoid valve
Introduction:
This solenoid valve is composed of a pilot valve and a main spool to form a channel combination; the normally closed type is in a closed state when it is not energized. When the coil is energized, the generated magnetic force makes the moving iron core and the static iron core pull together, the pilot valve port is opened, and the medium flows to the outlet. At this time, the pressure in the upper chamber of the main valve core is reduced, which is lower than the pressure on the inlet side, forming a pressure difference to overcome the spring. The resistance will move upwards accordingly to achieve the purpose of opening the main valve port, and the medium will flow. When the coil is powered off, the magnetic force disappears, and the moving iron core resets and closes the pilot port under the action of the spring force. At this time, the medium flows in from the balance hole, the pressure in the upper cavity of the main spool increases, and moves downward under the action of the spring force. Close the main valve port. The normally open principle is just the opposite.

3. Features of solenoid valve
1. External leakage is blocked, internal leakage is easy to control, and it is safe to use
Internal and external leaks are elements that endanger safety. Other automatic control valves usually extend the valve stem, and the rotation or movement of the valve core is controlled by electric, pneumatic and hydraulic actuators. All this needs to solve the problem of external leakage of the dynamic seal of the long-term action valve stem. Only the solenoid valve is completed by electromagnetic force acting on the iron core sealed in magnetic isolation sleeve, and there is no dynamic seal, so the external leakage is easy to block. The torque control of electric valve is not easy, it is easy to cause internal leakage, and even the head of valve stem is broken. The structure of solenoid valve is easy to control the internal leakage until it drops to zero. Therefore, the solenoid valve is particularly safe to use, especially for corrosive, toxic or high and low temperature media.

2. The system is simple, easy to connect to the industrial computer, and the price is low
The solenoid valve itself has a simple structure and low price, and is easier to install and maintain than other types of actuators such as control valves. What is more remarkable is that the composed automatic control system is much simpler and the price is much lower. Because the solenoid valve is controlled by switch signal, it is very convenient to connect with the industrial computer. In today's era of computer popularization and price drops, the advantages of solenoid valves are even more obvious.

3. Action, small power, light appearance
Solenoid valve response time can be as short as several milliseconds, and even pilot-operated solenoid valves can be controlled within tens of milliseconds. Because of its own loop, it is more sensitive than other automatic control valves. A properly designed solenoid valve coil has low power consumption and is an energy-saving product. It can also be achieved only by triggering the action to automatically maintain the valve position without power consumption at all. The solenoid valve has a small size, which saves space and is light and beautiful.

4. The adjustment accuracy and applicable medium are limited
Solenoid valves usually only have two states of on and off, the valve core can only be in two extreme positions, and cannot be adjusted continuously. The solenoid valve has high requirements on the cleanliness of the medium, and the medium containing particles cannot be applied. If it is an impurity, it must be filtered out first. In addition, viscous media cannot be used, and the range of media viscosity suitable for specific products is relatively narrow.

5. Diverse models and wide range of uses
Although the solenoid valve has inherent deficiencies, its advantages are still very prominent, so it is designed into a variety of products to meet various needs and has a wide range of uses. The advancement of solenoid valve technology also revolves around how to overcome congenital deficiencies and how to make better use of inherent advantages.

4. Solenoid valve selection
1. Economical
There are many solenoid valves that can be used in general. In the process of selection, the most economical product should be selected, but it must be economical on the basis of safety, application and reliability. Economy is not only the price of product, but also its function and quality, as well as the cost of installation, maintenance and other accessories. The most important is the cost of a solenoid valve in entire automatic control system and even in the production line is very small. If it is greedy for small and cheap and wrongly selected, it will cause huge damage. In a word, economy not only refers to product price, but also product performance-price ratio to comprehensive cost-price ratio.

2. Security
(1) Corrosive medium: plastic king solenoid valve and all stainless steel should be used. For strong corrosive medium, isolation diaphragm type must be used. For neutral medium, it is also advisable to use a solenoid valve with copper alloy as the valve casing material. Otherwise, rust chips often fall off in the valve casing, especially in the occasions where the action is not frequent. Ammonia valves cannot be made of copper.
(2) Explosive environment: Products with corresponding explosion-proof grades must be selected, and waterproof and dust-proof varieties should be selected for outdoor installation or in dusty occasions.
(3) The nominal pressure of solenoid valve should exceed the maximum working pressure in the pipe.

3. Reliability
(1) Working life, this item is not included in the factory test item, but belongs to the type test item. In order to ensure the quality, brand-name products from regular manufacturers should be selected.
(2) Work system: There are three types of long-term work system, repeated short-time work system and short-time work system. For the case where the valve is opened for a long time and only closed for a short time, a normally open solenoid valve should be used. When used in short-time working system and large batches, special orders can be made to reduce power consumption.
(3) Operating frequency: When the operating frequency is required to be high, the structure should preferably be a direct-acting solenoid valve, and the power supply should preferably be AC.
(4) Action reliability: Strictly speaking, this test has not been officially included in the professional standards of Taiwan's solenoid valves. In order to ensure the quality, brand-name products from regular manufacturers should be selected. In some occasions, the number of actions is not many, but the reliability requirements are very high, such as fire protection, emergency protection, must not be taken lightly. It is especially important to take two consecutive double insurances.

4. Applicability
(1) Medium characteristics
1.1 Choose different types of solenoid valves for gas, liquid or mixed state. For example, ZQDF is used for air, ZQDF-Y is used for liquid, and ZQDF-2 (or -3) is used for steam, otherwise it is easy to cause malfunction. ZDF series multi-function solenoid valve can be connected to gas and liquid. It is best to inform the state of the media when ordering, so that the installation user does not have to adjust the mode.
1.2 The medium temperature is different for products of different specifications, otherwise the coil will burn out and the seals will be aged, which will seriously affect the service life.
1.3 Medium viscosity, usually below 50cSt. If it exceeds this value, the ZDF series multi-function solenoid valve should be used for special order if the diameter is larger than 15mm. The diameter is less than 15mm to order high viscosity solenoid valve.
1.4 When the cleanliness of the medium is not high, a recoil filter valve should be installed in front of the solenoid valve. When the pressure is low, a direct-acting diaphragm solenoid valve can be used.
1.5 If the medium is in directional circulation, and reverse flow is not allowed, ZDF-N and ZQDF-N only need to use bidirectional circulation, please make special requirements.
1.6 The medium temperature should be selected within the allowable range of the solenoid valve.

(2) Pipeline parameters
2.1 Select the valve diameter and model according to the medium flow direction requirements and the pipeline connection method.
2.2 Select the nominal diameter according to the flow rate and Kv value of valve, or the same as the inner diameter of pipeline.
2.3 Working pressure difference, indirect pilot type can be used when the minimum working pressure difference is above 0.04Mpa; direct-acting type or step-by-step direct type must be used when the minimum working pressure difference is close to or less than zero.

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Question 4

Screen printing of electronic air pressure regulator

Accepted Answer

At present, silicon solar cells occupy most market of photovoltaic power, and are very important in terms of efficiency improvement and cost control. As an important part of silicon battery production, the screen printing of silicon battery electrodes directly affects the competitiveness of screen printing equipment in the market on the accuracy, efficiency and cost of printing equipment.

Screen printing is to attach a stencil with an image or a pattern to the screen for printing. When the substrate is placed directly under the screen with the stencil, the screen printing ink or paint passes through the extrusion of the squeegee. The mesh in the middle of the screen is printed on the carrier. One of the most important steps is the precision and pressure of the squeegee drop, which directly affects the layer thickness and shape of the printing, and even causes the silicon wafer to be damaged because the drop distance of the squeegee is too large. Therefore, the control of the squeegee is an important part of screen printing. The proportional pressure valve manufactured by KaoLu provides a comprehensive solution for screen printing equipment manufacturers with the advantages of high precision and high response.

KaoLu’s electronic air pressure regulator controls the corresponding pressure by controlling the input signal, and the output controls the corresponding movement of the cylinder to push the scraper speed to accurately drop to the required height, and transmit it to the controller in real time through the feedback signal. This is a method of pre-calculating the electronic air pressure regulator, which uses the linear characteristics of the electronic air pressure regulator to accurately control the pressure of screen printing blade to meet the accuracy required by the power system of screen printing machine. KaoLu’s electronic air pressure regulator adopts new technology, which enables it to achieve high control accuracy, and is widely used in the printing industry at present. KaoLu’s electronic air pressure regulator uses pneumatic components and semiconductor sensors to improve accuracy and response by adjusting the proportional pressure signal. The pressure control system of screen printing machine is composed of a electronic air pressure regulator, a screen printing scraper, a touch screen, a cylinder and a programmable logic controller. The schematic diagram is as follows:

Set the working pressure of silk screen scraper on the touch screen, the PLC controller will calculate and convert it into the digital quantity required by the analog output module, and the analog output module will output a certain voltage value to the proportional pressure valve. The electronic air pressure regulator will output the pressure according to the voltage signal, and the internal pressure sensor detects that the set pressure value is reached, that is, the pressure adjustment is completed.

Proportional pressure valves are not only used in the screen printing machine industry, but KaoLu’s electronic air pressure regulator can be widely used in industrial applications, automotive industry, inkjet industry and blow molding industry.

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Question 5

Technical Scheme of Vacuum Precision Control in Lunar Soil Environment Ground Simulation Test Device

Accepted Answer

Abstract: In the lunar exploration project, it is necessary to collect lunar soil samples in the vacuum environment of the lunar surface. It is necessary to establish a ground test device to simulate the vacuum thermal environment of the lunar surface to test the performance of the sample in vacuum thermal environment. Therefore, the degree of vacuum is required and it can achieve precise control. In this article, a technical scheme for accurate vacuum control using FC series proportional flow control valve is proposed for the ground simulation test device of vacuum thermal environment.

1. Question
In the lunar exploration project, it is necessary to collect lunar soil samples in the vacuum environment of the lunar surface. Therefore, a ground test device needs to be established to simulate the vacuum thermal environment of the lunar surface to test the performance of sample in the vacuum thermal environment, and accurate vacuum control is required to reach precise control. Due to the particularity of the lunar soil, vacuum control in current lunar soil ground model test device still needs to solve the following problems:
(1) Lunar soil and simulated lunar soil samples are generally powdery particles, so the pumping rate in the initial time should be strictly controlled to avoid dust generation.
(2) The current vacuum measurement and control also uses a Pirani vacuum gauge, which makes the matching control system unable to reach precise control of the vacuum, resulting in poor repeatability of the test results.
(3) The lunar soil ground simulation test device is generally small in size, and it has always been difficult to achieve precise control within a wide range of vacuum degrees. The fluctuation of vacuum degree is large, which is also one of the reasons for the poor repeatability of test results. Aiming at the above problems existing in the lunar soil ground model test device, this article focuses on corresponding technical solutions and introduces the detailed implementation process.

2. Technical Scheme
The overall structure of vacuum density control system of lunar soil environment ground simulation test equipment is shown in Figure 1. The whole system mainly includes a vacuum gauge, two proportional flow control valve, a PID controller and a vacuum pump. In order to do the precise control of the full range of vacuum degree, three capacitance vacuum gauges are generally required, and the measurement accuracy of vacuum gauge is 0.25%. In order to match the measurement accuracy of capacitance vacuum gauge, the controller adopts a high-precision PID controller with 24-bit A/D and 16-bit D/A, and the independent dual-channel facilitates the gas flow adjustment and control of the upstream proportional flow control valve and downstream proportional flow control valve control. The precise control of vacuum degree uses dynamic control mode, that is, the downstream proportional flow control valve is adjusted under low vacuum conditions, and the upstream proportional flow control valve is adjusted under high vacuum conditions. This is a typical forward and reverse control method, which can effectively ensure the control accuracy of vacuum degree. In conclusion, with this proven accurate vacuum control scheme, a control accuracy of better than 1% vacuum over the full scale range can be achieved.

For further information on different models of proportional flow control valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm

Question 6

Precision Vacuum Control to Reduce Solvent Loss in Evaporation and Concentration Process

Accepted Answer

Abstract: Aiming at the problems of precision vacuum control to reduce solvent loss in evaporation and concentration process, this article focuses on vacuum evaporation techniques, including the precise control method of vacuum degree, the simultaneous control method of vacuum degree and temperature, and the use of strong resistance of the corrosive electronic valve acts as a vacuum regulator.

1. Question
In the process of solvent extraction, the vacuum evaporation and concentration process is generally used. Since the solvent often has good volatility, the solvent is prone to loss during the vacuum extraction process, and sometimes the loss can reach 5~8%. Therefore, in order to solve the loss of solvent in the evaporation and concentration process, the following problems need to be solved:
(1) The precise control problem of vacuum degree, such as fixed-point control and program control, which is the key to reducing solvent loss.
(2) Simultaneous control problem of vacuum degree and temperature. This is because different vacuum degrees determine the boiling point of the solution. Through coordinated control of vacuum degree and temperature at the same time, the yield of the solvent can be greatly improved.
(3) In the vacuum evaporation and concentration process, many solvents and solutions are often corrosive to a certain extent, which requires the vacuum regulating valve to have good corrosion resistance. In order to solve the requirement of reducing solvent loss in the evaporation and concentration process, this article proposes a solution for precise control of vacuum degree, including the use of electronic flow control valve with strong corrosion resistance as vacuum degree control valves.

2. Solution
For the precise control of vacuum degree and temperature in the evaporation and concentration process, the overall structure of control system is shown in Figure 1.

(Figure 1 Schematic diagram of the vacuum degree and temperature control system structure of the evaporation and concentration process)

The basic principle of precise vacuum control is the dynamic control method, that is, according to the control set value and the measured value of vacuum gauge, the intake flow and exhaust flow of vacuum container are adjusted respectively, so that the flow in and out can reach a dynamic balance. If automatic control is required, PID control algorithms and corresponding controllers are required.

As shown in Figure 1, the accurate control proposal for vacuum degree control in this article adopts a dynamic control method, using an electronic flow control valve to adjust the intake flow, using an electronic ball valve or an electronic needle valve to adjust the exhaust flow, and the vacuum pump is used as a vacuum source. The automatic control of vacuum degree adopts PID controller.

In order to reach the temperature control function at the same time, this scheme adopts a dual-channel PID controller, one channel is used to control the vacuum degree, and another channel is used to control the temperature. This dual-channel PID controller is shown in Figure 2. This PID control has 24-bit A/D and 16D/A, with 47 input signal forms (thermocouple, thermal resistance, DC voltage), and can be connected to various vacuum and temperature sensors for measurement, display and control. It also has 2 independent measurement control channels, two-wire RS485, standard MODBUS RTU communication protocol.

(Figure 2 VPC2021 series dual-channel PID controller)

(Figure 3 FC series electronic needle valve)

In order to reach high-precision adjustment in the vacuum degree control process, an electronic needle valve with fine adjustment by a numerically controlled stepping motor is used, as shown in Figure 3. The hysteresis of this FC series proportional needle valves is much smaller than that of solenoid valves, and has a high-speed response within 1 second, especially the use of fluorine rubber (FKM) sealing technology, which makes the valve have superior corrosion resistance. Equipped with a stepper motor drive circuit module with the numerical control proportional needle valve, it provides the required power supply (24VDC) and control signal (0~10VDC) for the numerical control needle valve, and can also provide direct control of RS485 serial communication.

For larger-diameter air-extraction pipelines, a miniature proportional needle valve is used in this scheme, as shown in Figure 3. This series of proportional needle valve is a small electronic valve. The valve opening can be adjusted continuously according to the change of control signal (0~10VDC). The fastest opening and closing time is less than 7 seconds, and the opening and closing time can also reach less than 1 second. The integrated design of the valve and the valve body reduces external volume and is low in price. It is often installed between the sealed container and the vacuum pump to adjust pumping rate.

In short, through the solution described in this article, the vacuum degree control accuracy in the evaporation and concentration process can reach 1%, and the corresponding temperature control can also be carried out. The vacuum regulating valve has super corrosion resistance, which can effectively reduce the loss of solvent concentration during the vacuum evaporation process.

Question 7

Proposal for Vacuum Precision Control in Low Pressure Carburizing (LPC) Process

Accepted Answer

Abstract: In order to meet the requirements of precise control of vacuum degree in low-pressure carburizing process (vacuum carburizing), corresponding solutions are proposed in this article, including adding a gas mixing tank for permeate gas mixing, using upstream and downstream dynamic vacuum level control methods and vacuum degree by coordinating the control method with the temperature, the rapid and precise control of the vacuum degree and temperature in the infiltration process can be reached.

1. Question
Low-pressure carburizing, also known as vacuum carburizing, is a process in which a carburizing medium is passed into a high-temperature furnace for rapid carburizing under a low-pressure vacuum state. The vacuum carburizing process can be divided into one-stage type, pulse type and swing type. Among them, the degree of vacuum, temperature and carburizing time will change according to the specific requirement, especially the degree of vacuum will change drastically with the temperature change. Therefore, in the vacuum carburizing process, the following problems need to be solved in terms of vacuum degree control:

(1) The problem of fast and accurate control of vacuum degree, such as fixed-point control, program control and fast pulse control, requires the vacuum control system to have high response speed and control accuracy. Especially to achieve precise control in the full range of vacuum, it is necessary to use different vacuum sensors and corresponding upstream and downstream control modes according to different ranges.

(2) Simultaneous control problem of vacuum degree and temperature. The carburizing is carried out in a high temperature environment, requiring simultaneous control of vacuum degree and temperature.
In order to meet the requirements of precise control of vacuum degree in low-pressure carburizing process, this article focuses on a solution for precise control of vacuum degree, and adopts dual-channel PID control to reach synchronous temperature control.

2. Solution
The overall structure of the vacuum degree and temperature control system in the low pressure carburizing process is shown in Figure 1.

Figure 1 Schematic diagram of the structure of vacuum degree and temperature control system in low pressure carburizing process

The basic principle of precise control of vacuum degree is the dynamic control method, that is, according to the control set value and the measured value of vacuum gauge, the air intake flow and exhaust flow of the carburizing chamber are adjusted respectively, so that the flow in and out can reach a dynamic balance. If automatic control is required, PID control algorithms and corresponding controllers are required.

As shown in Figure 1, the precision control solution for vacuum degree proposed in this article adopts a dynamic control method, using an electronic needle valve to adjust the air intake flow, using an electronic ball valve or an electronic needle valve to adjust the exhaust flow, and the vacuum pump is used as a vacuum source. The automatic control of vacuum degree adopts PID controller.

For different low pressure carburizing processes, the control range of the vacuum degree is 1Pa~100kPa. Therefore, in the specific process, different dynamic control modes need to be adopted for the control in different vacuum degree ranges. For the vacuum degree control in the high vacuum range of 1Pa~1kPa, the upstream control mode of fixed exhaust flow and adjustable intake flow is adopted; for the vacuum degree control in the low vacuum range of 1kPa~100kPa, fixed intake flow and adjustable exhaust downstream control mode of the flow.

As shown in Figure 1, in order to reach the adjustment and control of air intake flow, a gas mixing tank is added to the intake end of carburizing chamber, and a gas mass flow meter is used to distribute various permeated gases into the gas mixing tank. The gas flows through the electronic needle valve for flow regulation and control.

In order to reach the temperature control function at the same time, this scheme adopts a dual-channel PID controller, one channel is used to control the vacuum degree, and the other channel is used to control the temperature. This dual-channel PID controller is shown in Figure 2. This PID control has 24-bit A/D and 16-bit D/A, with 47 input signal forms (thermocouple, thermal resistance, DC voltage), and can be connected to various vacuum and temperature sensors for measurement, display and control of 2 independent measurement control channels, two-wire RS485, standard MODBUS RTU communication protocol.

Figure 2 VPC2021 series dual-channel PID controller

Figure 3 FC series electronic needle valve

Figure 4 LCV-DS series electronic ball valve

In order to reach high-precision adjustment in the vacuum degree control process, an electronic needle valve with fine adjustment by a numerically controlled stepping motor is used, as shown in Figure 3. The hysteresis of FC series of needle valves is much smaller than that of solenoid valves, and has a high-speed response within 1 second, especially the use of fluorine rubber (FKM) sealing technology, which makes the valve have superior corrosion resistance. Equipped with a stepper motor drive circuit module with the numerical control electronic needle valve, it provides the required power supply (24VDC) and control signal (0~10VDC) for the numerical control needle valve, and can also provide direct control of RS485 serial communication.

For the larger diameter of the suction pipeline, this scheme uses a miniature electronic ball valve, as shown in Figure 4. This series of electronic ball valve is a small electronic valve. The valve opening can be adjusted continuously according to the change of the control signal (0~10VDC). The fastest opening and closing time is less than 7 seconds, and the opening and closing time can also reach less than 1 second. The integrated design of the valve and the valve body reduces the external volume and is low in price. It is often installed between the sealed container and the vacuum pump to adjust the pumping rate.

In conclusion, through the solution described in this article, the vacuum degree control accuracy in the low pressure carburizing process can reach 1% in the full scale range, and the corresponding temperature control can also be carried out.

Question 8

Ultra-Low Loss Single-Mode Optical Fiber Fused Taper Production by Accurate Vacuum Level Control Adsorption Fixture

Accepted Answer

Abstract: In the fiber fused taper system of fusion method, the fiber coupling with minimal loss corresponds to the optimal vacuum degree for adsorbing and fixing the optical fiber. Therefore, it is necessary to precisely control the adsorption vacuum degree and find the optimal vacuum degree value. In this article, focusing on the stable batch production of fiber fused taper system with minimal loss, an improvement scheme of vacuum system using FC series proportional flow control valve is proposed, which can reach precise control of vacuum degree.

1. Question
In the process of making optical fiber couplers and optical fiber cones in the optical fiber taper system, two or more optical fibers are generally positioned and clamped on the optical table by means of vacuum adsorption and special fixtures, and the two or more optical fibers are fixed in a certain way. A plurality of bare fibers are rotated and moved closer to the axis, heated and melted by a hydrogen-oxygen flame or a laser, and stretched to both sides at a certain speed, and finally a special waveguide structure in the form of a double cone is formed in the heating zone.

The current optical fiber taper technology is difficult to produce optical fiber couplers stably with a loss of less than 0.1 in batches, which is mainly due to the fact that optical fibers are fixed too tightly by vacuum adsorption. Some literatures reported that the vacuum system for adsorption and fixation fixture was improved, and the corresponding fiber couplers were fabricated under a series of different adsorption and fixation vacuum degrees, and it was proved that coupling loss in the entire vacuum degree range has a minimum area, When the vacuum degree is 120mBar, the minimum loss is 0.05dB, as shown in Figure 1.

As you can see from the results in Figure 1, it is not that the higher the vacuum degree, the better vacuum degree would be. The higher the vacuum degree, the tighter the fiber is fixed, and the coupling loss will be larger. It can be seen that in order to obtain an ultra-low loss fiber coupling device, it is necessary to precisely control the vacuum degree of the vacuum adsorption device.

In this article, according to the requirements for precise control of vacuum degree in the process of fabricating ultra-low loss optical fiber coupling devices by fiber taper method, a technical scheme of vacuum control system and corresponding supporting contents are proposed to reach precise and rapid control of vacuum degree.

Fig.1 Coupling loss under different vacuum pressures

2. Technical Scheme
In order to reach the precise control of adsorption vacuum degree in the left and right stretching fixtures, a vacuum tank is added to the original vacuum system. As long as the vacuum pressure in the vacuum tank is controlled, the adsorption vacuum degree of the left and right stretching fixtures can be controlled which shown in figure 2.

The vacuum degree control system shown in Figure 2 mainly includes an electronic needle valve, a vacuum gauge, a PID controller and a vacuum pump. The precise control of the vacuum degree adopts the dynamic control method, that is, according to the comparison between the measured value of the vacuum gauge and the set value, the PID controller adjusts the intake air flow and the exhaust air flow at the same time to quickly achieve dynamic balance and control the vacuum degree to the set value. , the control accuracy can reach ±1%.

In conclusion, through precise control of vacuum degree, stable mass production of ultra-low-loss fiber-coupled devices can be reached.

Figure 2 Schematic diagram of the vacuum degree control system of the fiber taper machine

Question 9

Electropneumatic Proportional Valve and Control Valve

Accepted Answer

Electropneumatic proportional valve is referred to as proportional valve, ordinary pneumatic valve can control the fixed value of equipment through pre-adjusted liquid flow pressure and flow. The feedback is reached by continuous changing speed of slow, fast and slow, or by simulating a good control curve with a certain precision to realize the force control. The ordinary pneumatic valve is controlled by pneumatic system of electropneumatic proportional valve.

Control valve consists of two main assemblies: valve body assembly and actuator assembly (or actuator system), which are divided into four series: single-seat series control valve, double-seat series control valve, sleeve cylinder series control valve and self-operated series control valve. Variations of four types of valves can lead to many different applicable configurations, each with its own specific applications, features, advantages and disadvantages. While some control valves are used in a wider range of applications than others, control valves are not suitable for all applications to work together to create the best solution for enhanced performance and reduced cost.

The electropneumatic valve is a pneumatic component that drives the valve core by an electromagnetic coil, while the control valve is a component that generates electromagnetic force through electromagnetic induction. The greater the current of the control valve, the greater the thrust, so will different energization currents for the common solenoid valve coils make the original on-off valve become a proportional valve?

This problem is obviously negative. Generally speaking, the internal processing of ordinary solenoid valves cannot achieve the processing accuracy of proportional valves. In addition, its internal structure does not consider too many parameters such as pneumatic pressure balance. Therefore, when the electromagnetic force is not large, the valve core cannot be stabilized in the transition position, and the electromagnetic switch valve cannot represent the proportional performance. Or the proportional performance of the solenoid switch valve is very inconspicuous. Therefore, the design and manufacturing process of proportional valves must be very different from those of on-off valves, requiring more investment in research and development.

Another question: For the same proportional valve, can the drive current of the solenoid coil be directly powered by the DC model without using the proportional amplifier? This method is possible in principle. The variable resistance signal can be used for coil control. However, it will waste a lot of energy, and at the same time, it will be accompanied by a lot of heat, and there will be no flutter and current when the valve core moves. Due to the feedback effect, the performance of the valve cannot be optimized.

In addition to the internal current feedback of the amplifier, the high-frequency dither signal is also an important function. The high-frequency flutter signal can keep the proportional spool vibrating at all times, so that it can overcome the influence of static friction and try to eliminate the influence of hysteresis on its performance.

A proportional amplifier is an electronic device used to provide a specific performance current to a proportional electromagnet, and to perform open-loop or closed-loop regulation of an electropneumatic proportional valve or electropneumatic proportional control system. So, what performance does the so-called specific performance current refer to?

To sum up, using a proportional amplifier can achieve the following functions: control the amount of current applied to the coil by the valve, set the minimum and maximum input signal of the proportional valve, set the minimum and maximum output current, and also set the ramp-up and ramp-down time, and finally set The frequency of the dither signal is obtained through the built-in current negative feedback function.
For further information about electropneumatic valve, please visit:
https://www.genndih.com/proportional-pressure-regulator.htm

Question 10

A Precise Control Method of Temperature and Pressure in Rayleigh-Brillouin Scattering Spectrometry

Accepted Answer

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.

Question 11

Vacuum Level and Temperature Control Method in Glove Box

Accepted Answer

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.

Question 12

Localized Electronic Air Flow Control Valve

Accepted Answer

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.

Technology