Anti-electromagnetic interference vacuum degree detection method

Abstract

The invention discloses an anti-electromagnetic interference vacuum degree detection method, which comprises a reaction tank, the reaction tank is connected with a mass flow meter, a high-frequency power supply, a vacuum pump and a vacuum gauge tube, the mass flow meter is connected with a reaction gas supply unit, and the vacuum gauge tube is connected with a PLC through an analog quantity to pulse output module; the vacuum pump vacuumizes the reaction tank, the mass flow meter controls the flow of gas conveyed into the reaction tank by the reaction gas supply unit, the vacuum gauge tube detects the vacuum degree in the reaction tank in real time and outputs a detection analog signal, and the analog quantity-pulse output module converts the detected analog quantity signal into a pulse frequency signal and inputs the pulse frequency signal into the PLC. And the PLC counts the number of the pulses through the counter and calculates to obtain a reduced analog signal, and the PLC controls the output of the mass flow meter through the reduced analog signal. According to the invention, the problem of poor vacuum degree measurement precision caused by electromagnetic interference can be effectively solved, and the reliability and controllability of the production process are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of vacuum detection, and particularly to a vacuum degree detection method with anti-electromagnetic interference. Background Art

[0002] In chemical vapor deposition and object surface treatment, some materials are not resistant to high temperatures and require low-temperature plasma reaction technology. To obtain low-temperature plasma, a high-frequency power supply is needed, especially a high-frequency power supply with a radio frequency of 13.56 MHz. This is a radio frequency and will generate strong electromagnetic waves. The above reactions must be carried out under vacuum conditions. Therefore, a vacuum gauge tube, a sensor for measuring the vacuum degree, is needed to transmit the analog signal of the vacuum degree of the reaction chamber to the analog-to-digital conversion module of the PLC. After being processed by the PLC, an analog quantity is output to the mass flowmeter, and the mass flowmeter can then control the gas volume entering the reaction chamber in real time, stably and continuously ensuring the reaction gas concentration in the reaction chamber, that is, the magnitude of the vacuum degree, so as to achieve the purpose of automated production.

[0003] Since the sensor obtains an analog signal, when transmitting it to the PLC, even if a shielded wire is used, electromagnetic interference cannot be completely eliminated. That is, no matter what, there will be electromagnetic induction, making the PLC unable to obtain the actual true vacuum degree, and thus unable to correctly control the reaction gas flow rate, making the production uncontrollable. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a vacuum degree detection method with anti-electromagnetic interference, which can effectively solve the problem of poor vacuum degree measurement accuracy caused by interference and ensure the reliability and controllability of the production process.

[0005] To solve the above technical problem, the present invention provides a vacuum degree detection method with anti-electromagnetic interference, including a reaction tank, which is connected with a mass flowmeter, a high-frequency power supply, a vacuum pump and a vacuum gauge tube. The mass flowmeter is connected to the reaction gas supply unit, and the vacuum gauge tube is connected to the PLC through an analog-to-pulse output module;

[0006] The vacuum pump evacuates the reaction tank, the mass flowmeter controls the flow rate of the reaction gas supplied by the reaction gas supply unit into the reaction tank, the vacuum gauge tube detects the vacuum degree in the reaction tank in real time and outputs a detection analog signal, the analog-to-pulse output module converts the detection analog signal into a pulse signal and inputs it into the PLC, and the PLC counts the pulse signal through a counter and calculates to obtain a restored analog signal, and the PLC controls the output of the mass flowmeter through the restored analog signal.

[0007] Further, when the counter counts the pulse signal, with time t as the counting period, the count value c obtained by counting is divided by time t to obtain the pulse frequency, and the magnitude of the pulse frequency represents the magnitude of the analog quantity, restoring the analog signal.

[0008] Further, after the analog-to-pulse output module inputs the pulse signal into the PLC, the counter starts counting. It does not count without input. After the counting cycle ends, the counter is cleared.

[0009] Further, two sets of data of the current x corresponding to the vacuum degree y of the vacuum gauge tube during detection are obtained through experiments. The two sets of data are linearly regressed to obtain the functional relationship between x and y as:

[0010] y = 863491x 4 - 1236.1x 3 + 6631.7x 2 - 15984x + 14825;

[0011] Substitute the restored analog signal as the current x into the functional relationship to calculate the corresponding vacuum degree y. The PLC controls the output of the mass flowmeter through the vacuum degree y.

[0012] Further, calculate the vacuum degree y when the restored analog signal obtained by calculation is between 3.50 mA and 4.32 mA.

[0013] Further, the PLC controls the output amount of the mass flowmeter by comparing the vacuum set value with the actual vacuum degree.

[0014] Further, it also includes a touch screen, and the touch screen is connected to the PLC.

[0015] Further, the vacuum set value has an allowable error range. Within the allowable error range, the steps for the PLC to control the mass flowmeter through the vacuum degree are as follows:

[0016] First, determine the standard adjustment interval (a, b) according to the vacuum set value Y and the allowable error range. a is the lower limit value of the vacuum degree, and b is the upper limit value of the vacuum degree. Then set the lower action adjustment interval (a, a1) and the upper action adjustment interval (b, b1), and set the interval (a1, b1) as the interval to be adjusted, where a < a1 < Y < b1 < b;

[0017] The PLC controls the mass flowmeter with at least three actual vacuum degrees calculated continuously as the judgment period. When the actual vacuum degrees calculated for the first and last times are within the interval to be adjusted, the mass flowmeter remains unadjusted; when the actual vacuum degree calculated for the first time is within the interval to be adjusted, and the actual vacuum degree calculated for the last time is within the lower action adjustment interval and / or the upper action adjustment interval, the mass flowmeter is adjusted based on the actual vacuum degree calculated for the last time; when the actual vacuum degree calculated for the first time is within the interval to be adjusted, and the actual vacuum degree calculated for the last time is within the lower action adjustment interval and / or the upper action adjustment interval, the mass flowmeter remains unadjusted; when the actual vacuum degrees calculated for the first and last times are within the lower action adjustment interval or the upper action adjustment interval, the mass flowmeter is adjusted based on the actual vacuum degree calculated for the last time; when the actual vacuum degree calculated for the first time is within the lower action adjustment interval or the upper action adjustment interval, and the actual vacuum degree calculated for the last time is within the interval to be adjusted, the mass flowmeter remains unadjusted.

[0018] Advantages of the present invention:

[0019] The present invention uses an analog-to-pulse output module, which outputs a pulse signal, that is, a switching quantity of on and off of the current. During the transmission of the switching quantity pulse, electromagnetic waves can only interfere with the magnitude of the current and cannot interfere with the presence or absence of the current, that is, they cannot interfere with the switching quantity. Therefore, the PLC counter is turned on for counting when there is current and turned off for non-counting when there is no current, without the need to judge the magnitude of the current, achieving the effect of completely blocking electromagnetic wave interference, making the control accurate and reliable, and ensuring the stability of production. Description of the drawings

[0020] Figure 1 is the flowchart of the detection method of the present invention

[0021] Figure 2 is the schematic diagram of the equipment structure connection of the present invention;

[0022] Figure 3 is the relationship curve diagram of the analog quantity and the vacuum degree of the present invention. Detailed implementation manners

[0023] The following further describes the present invention in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited do not limit the present invention.

[0024] Refer to Figures 1 to 3As shown in the figure, an embodiment of the vacuum degree detection method for anti-electromagnetic interference of the present invention includes a reaction tank 1, which is connected with a mass flowmeter 2, a high-frequency power supply 3, a vacuum pump 4 and a vacuum gauge 5. The mass flowmeter is connected to a reaction gas supply unit 6, and the vacuum gauge is connected to a PLC 8 through an analog-to-pulse output module 7; the PLC is also connected to a touch screen 9; the vacuum pump is used to evacuate the reaction tank, the mass flowmeter controls the flow rate of the reaction gas supplied by the reaction gas supply unit into the reaction tank, the vacuum gauge real-time detects the vacuum degree in the reaction tank and outputs a detection analog signal, the analog-to-pulse output module converts the detected analog signal into a pulse signal and inputs it into the PLC, the PLC counts the pulse signal through a counter and calculates to obtain a restored analog signal, and the PLC controls the output of the mass flowmeter through the restored analog signal.

[0025] During use, the vacuum gauge is directly connected to the analog-to-pulse output module, and the pulse signal output by the analog-to-pulse output module is connected to the counter of the PLC. The counter can count the number of pulses. To know the magnitude of the vacuum degree at a certain time, first clear the counter, the time relay T starts timing, trigger the counter C to start counting, and stop counting after t time. The restored analog signal at this time, that is, the analog quantity, is obtained by dividing the count value c obtained by the counter by the time t. The PLC can calculate the vacuum degree in the reaction tank at this time through calculation, and control the mass flowmeter through the vacuum degree, and then control the vacuum degree of the reaction tank, thus forming a complete closed loop.

[0026] Among them, two groups of data of the current x corresponding to the vacuum degree y of the vacuum gauge during detection are obtained through experiments, and the two groups of data are linearly regressed. Referring to Figure 3 As shown in the figure, the functional relationship between x and y is obtained as:

[0027] y = 86.491x 4 -1236.1x 3 +6631.7x 2 -15984x + 14825; by substituting the restored analog signal as the current x into the functional relationship, the corresponding vacuum degree y is calculated. The value of the vacuum degree y changes between 0 - 100, and the value of the current x only changes between 3.50 mA and 4.32 mA. The functional relationship in this change interval is not distorted, which is exactly the required detection range. The vacuum degree is calculated inside the PLC according to the functional relationship and compared with the set value, so as to determine the control of the valve opening size of the mass flowmeter to obtain the required vacuum degree.

[0028] The following are the measured data of the analog quantity and the vacuum degree:

[0029]

[0030]

[0031] In the table, it can be seen that each current value can correspond to a vacuum degree value. Based on the above measured data, the above function relationship can be effectively obtained. Through the function relationship, the vacuum degree value corresponding to the current value can be continuously and steplessly obtained, greatly improving the accuracy of the obtained vacuum degree value.

[0032] Specifically, when the reaction tank is not working, the vacuum gauge tube does not work and does not generate a detection analog signal, that is, the counter in the PLC does not count. When the reaction tank is in use, the vacuum pump evacuates, the mass flow meter cooperates with the reaction gas supply unit to transport gas into the reaction tank, and the vacuum gauge tube detects the vacuum degree in the reaction tank in real time and outputs a detection analog signal. The analog-to-pulse output module converts the detection analog signal into a pulse signal and inputs it into the PLC. When the PLC receives the signal and counts, with time t as the counting period, within one counting period, the reduced analog signal is obtained by dividing the counted value c obtained by counting by time t. According to the reduced analog signal, the vacuum degree corresponding to the current period can be obtained by substituting it into the linear regression equation. After the period ends, the counter needs to be cleared. Since the vacuum gauge tube continuously transmits signals during operation, the counter immediately enters the counting of the next period after the period ends, so as to continuously obtain the vacuum degree.

[0033] This application converts the analog quantity into a digital quantity, that is, a pulse, for transmission. The digital quantity will not be interfered by electromagnetic waves. Because the PLC counter turns on when it receives a digital quantity with current and turns off when there is no current, without judging the magnitude of the current. Therefore, electromagnetic waves can only interfere with the magnitude of the current and cannot interfere with the presence or absence of the current. And it effectively saves the PLC analog-to-digital conversion module and only uses the existing counter in the PLC, saving costs.

[0034] The vacuum set value has an allowable error range. Within the allowable error range, during the process of adjusting the gas supply by the mass flowmeter, the conventional method is to make real-time adjustments. Real-time adjustments can effectively ensure that the vacuum degree in the reaction tank always remains within the allowable error range of the vacuum set value. However, overly frequent adjustments are likely to shorten the service life of the mass flowmeter. And during use, due to reasons such as the internal operation of the reaction tank and the fluctuations of the vacuum pump itself, the vacuum degree inside the reaction tank will show slight fluctuations. This fluctuation does not necessarily lead to a continuous decrease or increase in the vacuum degree. Therefore, overly frequent adjustments will cause the fluctuation of the vacuum degree to become larger, posing higher requirements for regulation. And the method of not making adjustments within the allowable error range and then making adjustments after exceeding it will lead to overly lagged adjustments, resulting in larger fluctuations in the vacuum degree. Therefore, this application also provides a method for the PLC to control the mass flowmeter through the vacuum degree. Specifically, first determine the standard adjustment interval (a, b) according to the vacuum set value Y and the allowable error range, where a is the lower limit value of the vacuum degree and b is the upper limit value of the vacuum degree. Then set the lower action adjustment interval (a, a1) and the upper action adjustment interval (b, b1), and set the interval (a1, b1) as the interval to be adjusted, where a < a1 < Y < b1 < b;

[0035] The PLC controls the mass flowmeter with at least three continuously calculated actual vacuum degrees as the judgment period. When the actual vacuum degrees calculated for the first time and the last time are within the interval to be adjusted, it indicates that the vacuum degree in the reaction tank is within the required range, and the fluctuation of the vacuum degree value is not large and does not affect the use. Therefore, the mass flowmeter is not adjusted.

[0036] When the actual vacuum degree calculated for the first time is within the interval to be adjusted, and the actual vacuum degree calculated for the last time is within the lower action adjustment interval and / or the upper action adjustment interval, it indicates that the vacuum degree in the reaction tank is still within the required range, but the fluctuation of the vacuum degree value is relatively large, and there is a possibility of exceeding the allowable error range in subsequent several detections. Therefore, adjustments are needed to ensure that the actual vacuum degree tends to the vacuum set value, and the mass flowmeter is adjusted based on the actual vacuum degree calculated for the last time.

[0037] When the actual vacuum degree calculated for the first time is within the interval to be adjusted, and the actual vacuum degree calculated for the last time is within the lower action adjustment interval and / or the upper action adjustment interval, it indicates that the change in the vacuum degree in the reaction tank has relatively large fluctuations, and the vacuum degree is far from the vacuum set value, but it can still meet the usage requirements. It may be due to the internal fluctuations of the reaction tank causing the change in the vacuum degree, and re-judgment and observation are needed. Therefore, the mass flowmeter is not adjusted.

[0038] Based on the above situations that require re - judgment and observation, when the actual vacuum degree calculated for the first time is within the lower action adjustment range or the upper action adjustment range, and the actual vacuum degree calculated for the last time is within the range to be adjusted, the mass flowmeter is not adjusted.

[0039] When the actual vacuum degrees calculated for the first time and the last time are within the lower action adjustment range or the upper action adjustment range, it indicates that although the change in the vacuum degree in the tank is small, there is a possibility of exceeding the allowable error range in subsequent several detections. Therefore, adjustment is required to ensure that the vacuum degree tends to the vacuum set value, and the mass flowmeter is adjusted based on the actual vacuum degree calculated for the last time.

[0040] In the above - mentioned method, the adjustment of the opening degree of the mass flowmeter is in the existing manner and will not be elaborated.

[0041] In the above - mentioned method, by partitioning the allowable error range and based on the actual vacuum degree without interference, short - time hysteresis adjustment is carried out within the allowable error range, which can effectively avoid the problems caused by overly frequent adjustment and overly lagged adjustment, greatly reduce the fluctuation of the vacuum degree in the reaction tank, and has good adjustment effect and stability.

[0042] The above embodiments are only preferred embodiments given to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are within the protection scope of the present invention.

Claims

1. A vacuum degree detection method resistant to electromagnetic interference, characterized in that: It includes a reaction tank, the reaction tank is connected with a mass flow meter, a high-frequency power supply, a vacuum pump and a vacuum gauge, the mass flow meter is connected to a reaction gas supply unit, and the vacuum gauge is connected to a PLC through an analog quantity to pulse output module; The vacuum pump evacuates the reaction tank, the mass flow meter controls the reaction gas supply unit to deliver the reaction gas into the reaction tank, the vacuum gauge detects the vacuum degree in the reaction tank in real time and outputs the detection analog signal, the analog quantity to pulse output module converts the detected analog signal into a pulse signal and inputs it into the PLC, the size of the pulse frequency is used to represent the size of the analog quantity, the PLC counts the pulse signal through the counter, and calculates the restored analog signal, and the PLC controls the output of the mass flow meter by restoring the analog signal.

2. The vacuum degree detection method against electromagnetic interference according to claim 1, characterized in that: When the counter counts the pulse signal, the time t is used as the counting period, and the count value c obtained by counting is divided by the time t to obtain the restored analog signal.

3. The vacuum degree detection method against electromagnetic interference as claimed in claim 2, characterized in that: After the analog quantity to pulse output module inputs the pulse signal into the PLC, the counter starts counting. If there is no input, it will not count. After the counting cycle ends, the counter is cleared and counts for the next cycle.

4. The vacuum degree detection method against electromagnetic interference as claimed in claim 2, characterized in that: Through experiments, we get two sets of data of the current x corresponding to the vacuum degree y during the vacuum gauge detection. The two sets of data are linearly regressed to get the functional relationship between x and y: y=86.491x 4 -1236.1x 3 +6631.7x 2 -15984x+14825; Substitute the restored analog signal as the current x into the function relationship to calculate the corresponding vacuum degree y, and the PLC controls the output of the mass flow meter through the vacuum degree y.

5. The vacuum degree detection method against electromagnetic interference as claimed in claim 4, characterized in that: Calculate the vacuum degree y when the calculated reduced analog signal is between 3.50mA and 4.32mA.

6. The vacuum degree detection method against electromagnetic interference as claimed in claim 4, characterized in that: PLC controls the output of the mass flow meter by comparing the vacuum set value with the actual vacuum degree.

7. The vacuum degree detection method against electromagnetic interference according to claim 1, characterized in that: The utility model also comprises a touch screen, and the touch screen is connected with the PLC.

8. The vacuum degree detection method against electromagnetic interference as claimed in claim 6, characterized in that: The vacuum setting value has an allowable error range. Within the allowable error range, the steps of the PLC controlling the mass flow meter through the vacuum degree are as follows: First, determine the standard adjustment interval (a, b) according to the vacuum setting value Y and the allowable error range, where a is the lower limit of the vacuum degree and b is the upper limit of the vacuum degree. Then set the lower action adjustment interval (a, a1) and the upper action adjustment interval (b, b1), and set the interval (a1, b1) as the interval to be adjusted, where a <a1<Y<b1<b; The PLC controls the mass flow meter with at least three consecutively calculated actual vacuum degrees as the judgment cycle. When the actual vacuum degrees calculated for the first time and the last time are within the interval to be adjusted, the mass flow meter does not make adjustments; when the actual vacuum degree calculated for the first time is within the interval to be adjusted, and the actual vacuum degree calculated for the last time is within the lower action adjustment interval and / or the upper action adjustment interval, the mass flow meter is adjusted based on the actual vacuum degree calculated for the last time; when the actual vacuum degree calculated for the first time is within the interval to be adjusted, and the actual vacuum degree calculated for the last time is within the lower action adjustment interval and / or the upper action adjustment interval, the mass flow meter does not make adjustments; when the actual vacuum degree calculated for the first time and the last time is within the lower action adjustment interval or the upper action adjustment interval, the mass flow meter is adjusted based on the actual vacuum degree calculated for the last time; when the actual vacuum degree calculated for the first time is within the lower action adjustment interval or the upper action adjustment interval, and the actual vacuum degree calculated for the last time is within the interval to be adjusted, the mass flow meter does not make adjustments.

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