A slave capacitance thin film vacuum gauge readout device based on EtherCAT bus

Abstract

The present invention belongs to the field of vacuum measurement technology, and in particular relates to a slave capacitance thin film vacuum gauge readout device based on an EtherCAT bus. The device comprises a slave capacitance thin film vacuum gauge readout device based on an EtherCAT bus, comprising: an excitation signal generating module, a sensor interface module, a current-voltage conversion module, a bandpass filtering module, a precision rectification and filtering module, an analog output interface module, an analog-to-digital conversion module, a control circuit module, an EtherCAT bus module, and a power supply module. The slave capacitance thin film vacuum gauge based on the EtherCAT bus can be easily connected to the EtherCAT industrial Ethernet bus and has the characteristics of accurate data collection, high transmission efficiency, and simple wiring.

Description

Technical Field

[0001] The present invention belongs to the technical field of vacuum measurement, and in particular relates to a slave capacitance film vacuum gauge readout device based on an EtherCAT bus. Background Art

[0002] Traditional capacitance diaphragm vacuum gauge data acquisition devices typically rely on analog signal transmission, which can no longer meet the growing requirements of modern industrial control systems in terms of transmission efficiency, real-time responsiveness, and scalability. Integrating EtherCAT industrial Ethernet bus technology into capacitance diaphragm vacuum gauges, leveraging its superior data transmission characteristics, significantly improves data acquisition system performance and is of great significance for promoting the upgrade and optimization of industrial control systems. Summary of the Invention

[0003] In view of this, for application scenarios such as multi-channel vacuum acquisition systems and high-reliability vacuum acquisition, combined with the characteristics of easy networking of the EtherCAT industrial Ethernet bus and its strong anti-interference advantage, this application provides a slave capacitance film vacuum gauge readout device based on the EtherCAT bus. The slave capacitance film vacuum gauge based on the EtherCAT bus can be easily connected to the EtherCAT industrial Ethernet bus, and has the characteristics of accurate data acquisition, high transmission efficiency, simple wiring, etc. It can be widely used in the field of industrial vacuum measurement and has good application prospects.

[0004] The technical solutions for implementing the present invention are as follows:

[0005] A slave capacitance thin film vacuum gauge readout device based on EtherCAT bus, comprising: an excitation signal generating module, a sensor interface module, a current-voltage conversion module, a bandpass filtering module, a precision rectification and filtering module, an analog output interface module, an analog-to-digital conversion module, a control circuit module, an EtherCAT bus module and a power supply module; wherein,

[0006] The excitation signal generating module is used to generate a sinusoidal wave excitation signal;

[0007] The sensor interface module is used to send the excitation signal generated by the excitation signal generating module to the capacitance film vacuum gauge and receive the current signal sent back by the capacitance film vacuum gauge;

[0008] The current-voltage conversion module is used to convert the current signal sent back by the sensor and received by the sensor interface module into a voltage signal and output the voltage signal;

[0009] The bandpass filter module is used to filter out harmonic components in the output signal of the current-voltage conversion module;

[0010] The precision rectification and filtering module is used to rectify and filter the voltage signal output by the current-voltage conversion module;

[0011] The analog-to-digital conversion module is used to perform analog-to-digital conversion processing on the signal output by the precision rectification and filtering module;

[0012] The control circuit module is used to receive and process the signal output by the analog-to-digital conversion module;

[0013] The EtherCAT bus module is used to convert the signal processed by the control circuit module into an EtherCAT bus data signal and output it to the network interface;

[0014] The power supply module is used to provide power to each component unit of the entire system.

[0015] Furthermore, the excitation signal generating module of the present invention includes a Wien bridge oscillator circuit, a gain adjustment circuit and a rectifier filter circuit; wherein the Wien bridge oscillator circuit is composed of an operational amplifier and a precision resistor-capacitor circuit, and is used to generate a sinusoidal wave signal; the gain adjustment circuit is composed of a JFET and a resistor, and the JFET is connected in series in the feedback loop of the Wien bridge oscillator circuit, and is used for sinusoidal wave gain adjustment; the rectifier filter circuit is composed of a filter composed of a diode and an active integrator, and is used to rectify and process the signal into a relatively smooth DC signal; the positive electrode of the diode is connected to the output end of the Wien bridge oscillator circuit, and the output is connected to the gate of the JFET in the gain adjustment circuit.

[0016] Furthermore, the Wien bridge oscillator circuit of the present invention is mainly composed of an operational amplifier U 1.1 It is composed of a precision resistor-capacitor circuit consisting of resistors R1, R2, R3, R4 and capacitors C1 and C3, where resistor R1 and capacitor C1 are connected in series and then in parallel to the operational amplifier U 1.1 Between the same-direction input and output terminals, resistor R2 and capacitor C3 are connected in parallel and then connected to the operational amplifier U 1.1 Between the same-direction input terminal and ground, resistor R3 is connected in parallel with the operational amplifier U 1.1 Between the inverting input and output of the operational amplifier U 1.1 Connect the gain adjustment circuit through resistor R4;

[0017] The gain adjustment circuit is composed of a JFET and resistors R6 and R7. The resistor R4 of the Wien bridge oscillator circuit is connected in series with the resistor R6 and then grounded. The drain and source of the field effect transistor Q1 are connected in parallel to the two ends of the resistor R6. The gate of the field effect transistor Q1 is connected to the rectifier and filter circuit through the resistor R7.

[0018] The rectifier and filter circuit consists of a diode D1, an active integrator U 1.2, resistor R5 and capacitors C2 and C4, the gain adjustment circuit is connected to the active integrator U through the resistor R7 1.2 Output terminal, the capacitor C4 and the resistor R5 are connected in parallel to the active integrator U 1.2 Between the inverting input and output terminals of the Wien bridge oscillator circuit operational amplifier U 1.1 The output end is connected to the positive electrode of diode D1, and the negative electrode of diode is connected to the active integrator U 1.2 The inverting input terminal.

[0019] Furthermore, the current-voltage conversion module of the present invention is used to convert the current signal into a voltage signal, and is mainly composed of an operational amplifier U2, a feedback resistor R f and a zero adjustment resistor PR1; the feedback resistor is connected in series in the feedback loop of the operational amplifier, the center tap of the zero adjustment resistor is connected to the inverting input terminal of the operational amplifier, and the two ends are respectively connected to +VREF and -VREF; the current-voltage conversion module, its input end is the signal input terminal in the sensor interface module.

[0020] Furthermore, the bandpass filter module of the present invention is used to select the frequency of the useful signal and filter out the harmonic components, and is composed of a feedback network and an operational amplifier U1; the feedback network is composed of resistors R1, R2, and R3 capacitors, and the operational amplifier has a common-phase terminal connected to the negative pole of the power supply and an inverse-phase terminal connected to the feedback network; the input end of the bandpass filter module is connected to the output end of the current-voltage conversion module.

[0021] Furthermore, the precision rectification and filtering module of the present invention is mainly composed of a buffer, a precision rectification circuit and an RC low-pass filter; the buffer is composed of an operational amplifier U 2.1 The operational amplifier is connected to the output of the bandpass filter module in the same phase, and the inverting end is short-circuited with the output of the operational amplifier; the precision rectifier circuit is composed of the operational amplifier U 2.2 , resistor R 14 、R 12 、R 13 、R 17 , and diodes D2 and D3; the RC low-pass filter is composed of resistor R 15 Together with capacitor C8, resistor R 15 One end is connected to the output end of the precision rectifier circuit, and the other end serves as the output end of the precision rectifier and filter module and is connected to one end of capacitor C8, and the other end of the capacitor is connected to the power ground.

[0022] Furthermore, the analog output interface module of the present invention has one end J1 connected to C8 in the precision rectification and filtering module, and the other end J2 connected to the power ground, for outputting a 0-10V vacuum degree analog signal.

[0023] Furthermore, the analog-to-digital conversion module of the present invention is composed of a high-precision 24-bit ADC chip and its peripheral circuits, and the input end of the ADC chip is connected to the output end of the precision rectification and filtering module.

[0024] Furthermore, the control circuit module of the present invention is composed of a single-chip microcomputer and its peripheral circuits; the single-chip microcomputer is connected to the IO port of the ADC chip and is used for initializing the configuration of the registers of the ADC chip.

[0025] Furthermore, the EtherCAT bus module described in the present invention is composed of an EtherCAT control chip and its peripheral circuits, and an Ethernet RJ45 interface; its IO port is connected to the single-chip microcomputer in the control circuit module, and is used to receive control and data from the single-chip microcomputer; the Ethernet RJ45 interface is used to connect to the industrial Internet and complete data output.

[0026] Beneficial effects:

[0027] The circuit scheme of the present invention is simple. Compared with the previous vacuum metering equipment, the output result is a digital signal, which has strong anti-interference ability, long transmission distance and high reliability.

[0028] Using EtherCAT network bus as the output interface, it can be easily connected to the EtherCAT industrial Ethernet bus. It has the characteristics of accurate data collection, high transmission efficiency, simple wiring, etc., and can be widely used in the field of industrial vacuum measurement.

[0029] A 0-10V analog output interface is designed, which is backward compatible with the existing analog acquisition interfaces in industrial sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a circuit implementation module diagram of the present invention;

[0031] Figure 2 It is an excitation signal generating module circuit;

[0032] Figure 3 It is a sensor interface module;

[0033] Figure 4 It is a current-voltage conversion module circuit;

[0034] Figure 5 It is a bandpass filter module circuit;

[0035] Figure 6 It is a precision rectification and filtering module circuit;

[0036] Figure 7 It is the analog output interface module circuit;

[0037] Figure 8It is the relationship between the analog-to-digital conversion module, control circuit module, EtherCAT bus module, and power supply module. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0039] It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments may be combined with each other; and, based on the embodiments in this disclosure, all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of this disclosure.

[0040] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this disclosure, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement an apparatus and / or practice a method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this apparatus and / or practice this method.

[0041] like Figure 1 As shown, a slave capacitance thin film vacuum gauge readout method and circuit based on EtherCAT bus includes: an excitation signal generating module, a sensor interface module, a current-voltage conversion module, a bandpass filtering module, a precision rectification and filtering module, an analog output interface module, an analog-to-digital conversion module, a control circuit module, an EtherCAT bus module, and a power supply module;

[0042] The excitation signal generating module is used to generate a sinusoidal wave excitation signal; the sensor interface module is used to send the excitation signal generated by the excitation signal generating module to the capacitance film vacuum gauge and receive the current signal transmitted back by the capacitance film vacuum gauge; the current-voltage conversion module is used to convert the current signal transmitted back by the sensor received by the sensor interface module into a voltage signal and output it; the bandpass filtering module is used to filter out the harmonic components in the output signal of the current-voltage conversion module; the precision rectification and filtering module is used to rectify and filter the voltage signal output by the current-voltage conversion module; the analog-to-digital conversion module is used to perform analog-to-digital conversion on the signal output by the precision rectification and filtering module; the control circuit module is used to receive the signal output by the analog-to-digital conversion module for processing; the EtherCAT bus module is used to convert the signal processed by the control circuit module into an EtherCAT bus data signal and output it to the network interface; the power supply module is used to provide power to each component unit of the entire system.

[0043] The excitation signal generation module generates a sinusoidal excitation signal. This high-precision signal source is fed into the sensor, causing it to output a signal containing information about its capacitance. The principle is that capacitors of varying capacitance exhibit varying capacitive reactance under the influence of the same excitation signal, resulting in a signal current related to the sensor's capacitance. The sensor's output signal undergoes current-to-voltage conversion, which is then conditioned, harmonics filtered, and precision rectified to produce a DC signal with an amplitude linearly related to the sensor's capacitance. This signal is then acquired using a digital-to-analog converter (DAC), converted to vacuum level, and transmitted via the EtherCAT bus, completing the entire detection process. This portion of the circuitry, from the excitation signal to the analog-to-digital conversion stage, primarily converts capacitance to voltage, a process known as capacitance-to-voltage conversion.

[0044] like Figure 2As shown, in the embodiment of the present application, the stability of the detection result is directly related to the amplitude stability of the sinusoidal signal used. In view of this, a Wien bridge oscillator circuit including an automatic gain control mechanism is designed to generate a sinusoidal signal to ensure the stability of the excitation signal amplitude. It includes a Wien bridge oscillator circuit, a gain adjustment circuit and a rectifier filter circuit; wherein, the Wien bridge oscillator circuit is composed of an operational amplifier and a precision resistor-capacitor circuit, which is used to generate a sinusoidal wave signal; the gain adjustment circuit is composed of a JFET (junction field effect transistor) and a resistor, and the JFET is connected in series in the feedback loop of the Wien bridge oscillator circuit for sinusoidal wave gain adjustment; the rectifier filter circuit is composed of a filter composed of a diode and an active integrator, which is used to rectify and process the signal into a relatively smooth DC signal; the positive pole of the diode is connected to the output end of the Wien bridge oscillator circuit, and the output is connected to the gate of the JFET in the gain adjustment circuit. The circuit is specifically as follows:

[0045] The Wien bridge oscillator circuit is mainly composed of the operational amplifier U 1.1 It is composed of a precision resistor-capacitor circuit consisting of resistors R1, R2, R3, R4 and capacitors C1 and C3, where resistor R1 and capacitor C1 are connected in series and then in parallel to the operational amplifier U 1.1 Between the same-direction input and output terminals, resistor R2 and capacitor C3 are connected in parallel and then connected to the operational amplifier U 1.1 Between the same-direction input terminal and ground, resistor R3 is connected in parallel with the operational amplifier U 1.1 Between the inverting input and output of the operational amplifier U 1.1 Connect the gain adjustment circuit through resistor R4;

[0046] The gain adjustment circuit is composed of a JFET (junction field effect transistor) and resistors R6 and R7. The resistor R4 of the Wien bridge oscillator circuit is connected in series with the resistor R6 and then grounded. The drain and source of the field effect transistor Q1 are connected in parallel to the two ends of the resistor R6. The gate of the field effect transistor Q1 is connected to the rectifier and filter circuit through the resistor R7.

[0047] The rectifier and filter circuit consists of a diode D1, an active integrator U 1.2 , resistor R5 and capacitors C2 and C4, the gain adjustment circuit is connected to the active integrator U through the resistor R7 1.2 Output terminal, the capacitor C4 and the resistor R5 are connected in parallel to the active integrator U 1.2 Between the inverting input and output terminals of the Wien bridge oscillator circuit operational amplifier U 1.1 The output end is connected to the positive electrode of diode D1, and the negative electrode of diode is connected to the active integrator U 1.2 The inverting input terminal.

[0048] The principle diagram of excitation signal generation is as follows Figure 2As shown, Q1 uses a zero-temperature-coefficient junction field-effect transistor (JFET) to replace the diode in the traditional Wien bridge oscillator solution and is connected to the feedback circuit as a gain adjustment element. This design can greatly enhance the adaptability of the sinusoidal signal output to ambient temperature changes, thereby achieving higher temperature stability and improving the reliability of the results of the entire detection process. Diode D1 samples and rectifies the signal output, and then sends it to C4, R5 and the operational amplifier U 1.2 The low-pass filter formed by the output smooth DC signal is used to control the gate of Q1. 1.1 In the feedback loop, the output signal amplitude can be controlled by adjusting the gate voltage of Q1 to achieve the purpose of amplitude stabilization. 1.2 The reference voltage V REF The size of can change the output amplitude of the oscillation circuit. Since R1, C1, R2, C2 jointly determine the frequency of the Wien bridge oscillation circuit, and the capacitive reactance of the measured capacitor X c It is also related to the excitation signal frequency f, so R1, C1, R2, and C2 are selected to be high-precision and low-temperature drift devices.

[0049] like Figure 3 As shown, the analog output interface module of the embodiment of the present application has one end J1 connected to C8 in the precision rectification and filtering module, and the other end J2 connected to the power ground, for outputting a 0-10V vacuum degree analog signal.

[0050] Figure 4 As shown, the current-voltage conversion module in the embodiment of the present application is used to convert the current signal into a voltage signal, which is composed of an operational amplifier U2, a feedback resistor R f , zero adjustment resistor PR1 and capacitor C X The feedback resistor is connected in series in the feedback loop of the operational amplifier, the center tap of the zero adjustment resistor is connected to the same-direction input terminal of the operational amplifier, and the two ends are connected to +VREF and -VREF respectively; the input terminal of the current-voltage conversion module is connected in series with a capacitor C X Then connect to the signal input terminal J2 in the sensor interface module.

[0051] The basic principle of current-voltage conversion is that the excitation signal is sent to one end of the capacitor to be measured, and the current signal output from the other end is generated by U2 and R f The current-voltage conversion circuit composed of the above circuits converts the current into voltage and then outputs it. x For the capacitor to be measured, in actual application, the sensor is connected to C x PR1 is a zero adjustment potentiometer, used to adjust the output zero point.

[0052] like Figure 5As shown, the bandpass filter module of the embodiment of the present application is used to select the frequency of the useful signal and filter out the harmonic components. It is composed of a feedback network and an operational amplifier U1; the feedback network is composed of resistors R1, R2, R3 and capacitors C1 and C2. The operational amplifier has a non-inverting terminal connected to the negative pole of the power supply and an inverting terminal connected to the feedback network; the input end of the bandpass filter module is connected to the output end of the current-voltage conversion module. Specifically, the non-inverting input end of the operational amplifier U1 is grounded, the inverting input end is connected in series with capacitor C2 and resistor R1, and then connected to the output end of the current-voltage conversion module. Resistor R1 and capacitor C2 are grounded through resistor R2, and connected to the output end of amplifier U1 through capacitor C1. Resistor R3 is connected between the inverting input end and the output end of amplifier U1.

[0053] The voltage signal output by the current-voltage conversion circuit is essentially an amplitude modulated signal. Figure 4 The AM signal output by the circuit contains a large number of harmonic components in addition to the fundamental frequency. In order to make the subsequent processing easier, it is necessary to extract the fundamental frequency component containing useful information. Figure 2 The frequency of the generated excitation signal is known, so we can design a bandpass filter that only allows the known frequency to pass. Figure 5 The schematic diagram of the active bandpass filter used in this design is shown. When C1=C2=C, the size of the capacitor C does not affect the gain H(jf0) and quality factor Q of the bandpass filter. Therefore, its capacitance value is usually determined by engineering experience. For example, the selection range for the frequency of 10kHz-100kHz is 1000pF-100pF. In this invention, C1=C2=470pF is selected.

[0054] like Figure 6 As shown, the precision rectification and filtering module of the embodiment of the present application is composed of a buffer, a precision rectification circuit and an RC low-pass filter; the buffer is composed of an operational amplifier U 2.1 The operational amplifier is connected to the output of the bandpass filter module in the same phase, and the inverting end is short-circuited with the output of the operational amplifier; the precision rectifier circuit is composed of the operational amplifier U 2.2 , resistor R 12 、R 13 、R 14 、R 17 And diodes D2, D3; the operational amplifier U 2.2 The inverting input is connected to the resistor R 14 Connect to operational amplifier U 2.1 The output of the operational amplifier U 2.2 The non-inverting input terminal is connected to the resistor R 17 Ground, operational amplifier U 2.2The output end of the precision rectifier circuit is connected in series with the diode D2, and the resistor R 13 Connected in series with diode D3 and then in parallel with operational amplifier U 2.2 Between the inverting input and output terminals, the resistor R 12 Connected in parallel to the operational amplifier U 2.2 The RC low-pass filter is connected between the inverting input terminal and the output terminal of the precision rectifier circuit; 15 Together with capacitor C8, resistor R 15 One end is connected to the output end of the precision rectifier circuit, and the other end serves as the output end of the precision rectifier and filter module and is connected to one end of capacitor C8, and the other end of the capacitor is connected to the power ground.

[0055] The signal output by the active filter is an amplitude modulated signal with the same frequency as the excitation signal, and its amplitude value is related to the capacitance being measured. Since the vacuum degree of the measured environment changes relatively slowly when the vacuum sensor is working, its capacitance also changes relatively slowly, and the output capacitance is usually a monotonic function within the effective range. Therefore, it is only necessary to extract the amplitude of the amplitude modulated signal. The present invention uses a precision rectifier circuit to complete the extraction of the amplitude signal, such as Figure 6 As shown in the figure, the input signal first passes through U 2.1 Isolation buffer to eliminate the mutual influence between the front and back stages as much as possible. 15 Together with C8, it forms a low-pass filter to filter the signal output by the rectifier circuit. The output end will be directly connected to the input end of the ADC acquisition circuit. 15 =1kΩ, C8 =10uF, select 24-bit AD7732 for analog-to-digital conversion, its input range can reach ±10V, the ADC acquisition circuit uses the application circuit recommended in the AD7732 manual to meet the needs of this design.

[0056] like Figure 7 As shown, the analog output interface module has one end J1 connected to C8 in the precision rectification and filtering module, and the other end J2 connected to the power ground, for outputting a 0-10V vacuum degree analog signal.

[0057] like Figure 8 As shown, the control circuit module described in the embodiment of the present application is composed of a single-chip microcomputer and its peripheral circuits; the single-chip microcomputer is connected to the IO port of the ADC chip and is used for register initialization configuration of the ADC chip.

[0058] This embodiment uses LAN9252 as the EtherCAT slave controller. The designed EtherCAT slave circuit diagram is as follows: Figure 8LAN9252 sets up a slave station by reading the configuration information in the external EEPROM. After the configuration is completed, the microcontroller can communicate with LAN9252 through the SPI serial or parallel mode PDI interface.

[0059] The microcontroller is the core of the entire capacitance thin film vacuum gauge control section and has three main functions: first, it configures the ADC registers, completes the hardware-level control of ADC data conversion, and preprocesses the obtained data, such as digital filtering; second, it performs calculations on the collected data, such as parameter fitting and vacuum degree conversion; and third, it serves as the control core of the EtherCAT slave station and uses its own hardware SPI interface module to complete communication with the LAN9252.

[0060] The power supply part provides power for the whole machine, with one DC24V input and three groups of DC3.3V, DC5V and DC±12V power output.

[0061] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A slave capacitance thin film vacuum gauge readout device based on EtherCAT bus, characterized in that: include: Excitation signal generation module, sensor interface module, current-voltage conversion module, bandpass filter module, precision rectification and filtering module, analog output interface module, analog-to-digital conversion module, control circuit module, EtherCAT bus module and power supply module; among them, The excitation signal generating module is used to generate a sinusoidal wave excitation signal; The sensor interface module is used to send the excitation signal generated by the excitation signal generating module to the capacitance film vacuum gauge and receive the current signal sent back by the capacitance film vacuum gauge; The current-voltage conversion module is used to convert the current signal sent back by the sensor and received by the sensor interface module into a voltage signal and output the voltage signal; The bandpass filter module is used to filter out harmonic components in the output signal of the current-voltage conversion module; The precision rectification and filtering module is used to rectify and filter the voltage signal output by the current-voltage conversion module; The analog-to-digital conversion module is used to perform analog-to-digital conversion processing on the signal output by the precision rectification and filtering module; The control circuit module is used to receive and process the signal output by the analog-to-digital conversion module; The EtherCAT bus module is used to convert the signal processed by the control circuit module into an EtherCAT bus data signal and output it to the network interface; The power supply module is used to provide power to each component unit of the entire system.

2. The EtherCAT bus-based slave capacitance thin film vacuum gauge readout device according to claim 1, characterized in that: The excitation signal generating module includes a Wien bridge oscillator circuit, a gain adjustment circuit, and a rectifier and filter circuit; wherein the Wien bridge oscillator circuit is composed of an operational amplifier and a precision resistor-capacitor circuit, and is used to generate a sinusoidal wave signal; the gain adjustment circuit is composed of a JFET and a resistor, and the JFET is connected in series in the feedback loop of the Wien bridge oscillator circuit, and is used for sinusoidal wave gain adjustment; the rectifier and filter circuit is composed of a filter composed of a diode and an active integrator, and is used to rectify and process the signal into a relatively smooth DC signal; the positive electrode of the diode is connected to the output end of the Wien bridge oscillator circuit, and the output is connected to the gate of the JFET in the gain adjustment circuit.

3. The EtherCAT bus-based slave capacitance thin film vacuum gauge readout device according to claim 2, characterized in that: The Wien bridge oscillator circuit is mainly composed of an operational amplifier U 1.1 and by the resistor R 1. R 2. R 3. R 4 and capacitor C 1. C 3 composed of precision resistor and capacitor circuit, in which the resistor R 1 and capacitor C 1 connected in series and then in parallel with the operational amplifier U 1.1 Between the non-inverting input and output, the resistor R 2 and capacitor C 3 in parallel and then connected to the operational amplifier U 1.1 Between the non-inverting input terminal and ground, the resistor R 3 in parallel with the operational amplifier U 1.1 Between the inverting input and output of the operational amplifier U 1.1 Through the resistor R 4. Connect the gain adjustment circuit; The gain adjustment circuit consists of JFET and resistor R 6. R 7. The resistance of the Wien bridge oscillator circuit R 4 series resistors R 6 back ground, field effect transistor Q The drain and source of 1 are connected in parallel with the resistor R 6, the FET Q 1's gate is connected through a resistor R 7. Connect the rectifier and filter circuit; The rectifier and filter circuit consists of a diode D 1. Active integrator U 1.2 ,resistance R 5 and capacitors C 2. C 4, the gain adjustment circuit is composed of resistors R 7. Connect the active integrator U 1.2 output terminal, the capacitor C 4 and resistors R 5 in parallel with the active integrator U 1.2 Between the inverting input and output terminals of the Wien bridge oscillator circuit operational amplifier U 1.1 The output terminal and the diode D 1 The positive pole is connected to the cathode of the diode and the active integrator U 1.2 The inverting input terminal.

4. The EtherCAT bus-based slave capacitance thin film vacuum gauge readout device according to claim 1, characterized in that: The current-voltage conversion module is used to convert the current signal into a voltage signal, and is mainly composed of an operational amplifier U2, a feedback resistor R f and a zero adjustment resistor PR1; the feedback resistor is connected in series in the feedback loop of the operational amplifier, the center tap of the zero adjustment resistor is connected to the non-inverting input terminal of the operational amplifier, and the two ends are respectively connected to +VREF and -VREF; the input end of the current-voltage conversion module is connected to the signal input terminal in the sensor interface module.

5. The EtherCAT bus-based slave capacitance thin film vacuum gauge readout device according to claim 1, characterized in that: The bandpass filter module is used to select the frequency of the useful signal and filter out the harmonic components. It is composed of a feedback network and an operational amplifier U1. The feedback network is composed of resistors R1, R2, R3, and a capacitor. The operational amplifier has a common-phase terminal connected to the negative pole of the power supply and an inverse-phase terminal connected to the feedback network. The input end of the bandpass filter module is connected to the output end of the current-voltage conversion module.

6. The EtherCAT bus-based slave capacitance thin film vacuum gauge readout device according to claim 1, characterized in that: The precision rectification and filtering module is mainly composed of a buffer, a precision rectification circuit and an RC low-pass filter; the buffer is composed of an operational amplifier U 2.1 The operational amplifier is connected to the output of the bandpass filter module in the same phase, and the inverting end is short-circuited with the output of the operational amplifier; the precision rectifier circuit is composed of the operational amplifier U 2.2 , resistor R 14 、R 12 、R 13 、R 17 , and diodes D2 and D3; the RC low-pass filter is composed of resistor R 15 Together with capacitor C8, resistor R 15 One end is connected to the output end of the precision rectifier circuit, and the other end serves as the output end of the precision rectifier and filter module and is connected to one end of capacitor C8, and the other end of the capacitor is connected to the power ground.

7. The EtherCAT bus-based slave capacitance thin film vacuum gauge readout device according to claim 6, characterized in that: The analog output interface module has one end J1 connected to C8 in the precision rectification and filtering module, and the other end J2 connected to the power ground, and is used to output a 0~10V vacuum degree analog signal.

8. The EtherCAT bus-based slave capacitance thin film vacuum gauge readout device according to claim 1, characterized in that: The analog-to-digital conversion module is composed of a high-precision 24-bit ADC chip and its peripheral circuits, and the input end of the ADC chip is connected to the output end of the precision rectification and filtering module.

9. The EtherCAT bus-based slave capacitance thin film vacuum gauge readout device according to claim 1, characterized in that: The control circuit module is composed of a single-chip microcomputer and its peripheral circuits; the single-chip microcomputer is connected to the IO port of the ADC chip and is used for initializing the configuration of the registers of the ADC chip.

10. The EtherCAT bus-based slave capacitance thin film vacuum gauge readout device according to claim 1, characterized in that: The EtherCAT bus module consists of an EtherCAT control chip and its peripheral circuits, and an Ethernet RJ45 interface; its IO port is connected to the single-chip microcomputer in the control circuit module and is used to receive control and data from the single-chip microcomputer; the Ethernet RJ45 interface is used to connect to the industrial Internet and complete data output.

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