阅读说明：本技术 电容式薄膜真空计检测电路、真空计及真空度检测方法 (Detection circuit of capacitance type film vacuum gauge, vacuum gauge and vacuum degree detection method ) 是由 王松杰 汤一 王杰 宋冬谊 高乐 韩雪飞 廖兴才 林立男 张永斌 于 2021-12-09 设计创作，主要内容包括：本发明提供一种电容式薄膜真空计检测电路、真空计及真空度检测方法,本发明提供的电容式薄膜真空计检测电路、真空计及真空度检测方法,通过独立且反相的载波信号分别对薄膜电容的内环电容信号和外环电容信号进行调制,对调制后的内环电容信号和外环电容信号进行求和得到电容差值信号,进而换算得到真空度检测结果,由于调制后的内环电容信号和外环电容信号通过求和的方式即可获得电容差值,对电路中器件的性能要求较低,能够保证真空度检测结果线性度更高且更加稳定可靠。(The invention provides a detection circuit, a vacuum gauge and a vacuum degree detection method for a capacitive film vacuum gauge, which are characterized in that an inner ring capacitance signal and an outer ring capacitance signal of a film capacitor are respectively modulated by independent and opposite-phase carrier signals, the modulated inner ring capacitance signal and the modulated outer ring capacitance signal are summed to obtain a capacitance difference signal, and then a vacuum degree detection result is obtained through conversion.)

1. A capacitive thin film gauge detection circuit, comprising: the capacitive test board comprises a capacitive detection module, a first processor and a first power supply module, wherein the capacitive detection module is electrically connected with the first processor, and the first power supply module is electrically connected with the capacitive detection module and the first processor respectively;

the capacitance detection module is used for modulating an inner ring capacitance signal and an outer ring capacitance signal of the thin film capacitor respectively through independent and opposite-phase carrier signals, summing the modulated inner ring capacitance signal and the modulated outer ring capacitance signal to obtain a capacitance difference signal, and transmitting the capacitance difference signal to the first processor, wherein the first processor is used for calculating and processing the capacitance difference signal to obtain a vacuum degree detection result.

2. The detection circuit of claim 1, wherein the capacitance detection module comprises a thin film capacitor, a digital-to-analog converter, a first operational amplifier, a second operational amplifier, an adder circuit, and an analog-to-digital converter;

the digital-to-analog converter is used for outputting a first carrier signal and a second carrier signal, and the first carrier signal and the second carrier signal are independent and in opposite phase;

the first carrier signal and an inner ring capacitance signal of the thin film capacitor are input into the first operational amplifier, and are modulated and amplified by the first operational amplifier to output a first modulation signal;

the second carrier signal and the outer ring capacitance signal of the thin film capacitor are both input into the second operational amplifier, and are modulated and amplified by the second operational amplifier to output a second modulation signal;

the first modulation signal and the second modulation signal are input into the addition circuit, summed by the addition circuit and output to a capacitance difference signal, and the capacitance difference signal is subjected to analog-to-digital conversion by the analog-to-digital converter and input to the first processor.

3. The detection circuit of claim 1, wherein said capacitive test board further comprises a first temperature sensor, said first temperature sensor is electrically connected to said first processor, and said first temperature sensor is configured to collect temperature information of said capacitive test board.

4. The detection circuit of claim 1, further comprising a thermal control board electrically connected to the capacitive test board;

the temperature control board comprises a temperature control module, a second processor and a second power supply module, the temperature control module is electrically connected with the second processor, and the second power supply module is respectively electrically connected with the temperature control module and the second processor;

the temperature control module is used for collecting temperature information of the surrounding environment of the temperature control plate and transmitting the temperature information of the surrounding environment of the temperature control plate to the second processor, the second processor is used for analyzing and processing the temperature information of the surrounding environment of the temperature control plate to generate a temperature control instruction, and transmits the temperature control instruction to the temperature control module, and the temperature control module is further used for executing heating or stopping heating according to the temperature control instruction.

5. The detection circuit of claim 4, wherein the temperature control module comprises a thermistor and a heater, and both the thermistor and the heater are electrically connected to the second processor;

the thermistor is used for collecting temperature information of the surrounding environment of the temperature control plate, and transmitting the temperature information of the surrounding environment of the temperature control plate to the second processor, the second processor analyzes and processes the temperature information of the surrounding environment of the temperature control plate, generates a temperature control instruction, and transmits the temperature control instruction to the heater, and the heater is used for executing heating or stopping heating according to the temperature control instruction.

6. The detection circuit of claim 5, wherein the temperature control module further comprises a second temperature sensor electrically connected to the second processor, the second temperature sensor being configured to collect temperature information of the thermal control plate and transmit the temperature information of the thermal control plate to the second processor.

7. The detection circuit of claim 4, wherein the thermal control board further comprises a key module, the key module is electrically connected to the second processor, and the key module is configured to receive the zeroing and fine-tuning control trigger signal.

8. The detection circuit of claim 4, wherein the thermal control board further comprises an indicator light module, the indicator light module is electrically connected to the second processor, and the indicator light module is used for indicating the operating status of the thermal control board and the capacitive test board.

9. A vacuum gauge comprising a capacitive thin film gauge detection circuit as claimed in any one of claims 1to 8.

10. A method of detecting a degree of vacuum, comprising:

the inner ring capacitance signal and the outer ring capacitance signal of the film capacitor are respectively modulated through independent and opposite-phase carrier signals;

summing the modulated inner ring capacitance signal and the modulated outer ring capacitance signal to obtain a capacitance difference signal;

and calculating the capacitance difference signal to obtain a vacuum degree detection result.

Technical Field

The invention relates to the technical field of vacuum measurement, in particular to a detection circuit of a capacitance type film vacuum gauge, the vacuum gauge and a vacuum degree detection method.

Background

The vacuum gauge, also called vacuum gauge, is mainly used to measure the vacuum degree and the pressure. Vacuum gauges can be classified into different categories according to different working principles. The capacitance type thin film vacuum gauge has the advantages of high sensitivity, low temperature coefficient, low power consumption and the like, and is widely applied. The detection circuit as a key component of the capacitance type film vacuum gauge has great influence on various performance indexes of the capacitance type film vacuum gauge, such as noise indexes, scale factor nonlinear indexes, stability indexes and the like.

At present, a detection circuit of a capacitance type film vacuum gauge is mainly built on the basis of an LC or RC oscillating circuit, although the sensitivity of the detection circuit is relatively high, the conversion linearity is poor, the complexity of subsequent signal processing is greatly increased, and the structure of the detection circuit is complex. In addition, there is a detection scheme based on a diode bridge circuit, and although the detection circuit has a simple structure, the noise is relatively large, and the stability of the measurement result is low.

Therefore, the existing detection circuit of the capacitance type film vacuum gauge has the problems of complex structure and unstable and reliable measurement result, and is difficult to meet the requirements of practical application.

Disclosure of Invention

The invention provides a detection circuit of a capacitance film vacuum gauge, the vacuum gauge and a vacuum degree detection method, which are used for solving the defects that the detection circuit of the capacitance film vacuum gauge in the prior art is complex in structure and the measurement result is not stable and reliable enough.

In a first aspect, the present invention provides a detection circuit for a capacitive thin film gauge, comprising: the capacitive test board comprises a capacitive detection module, a first processor and a first power supply module, wherein the capacitive detection module is electrically connected with the first processor, and the first power supply module is electrically connected with the capacitive detection module and the first processor respectively;

the capacitance detection module is used for modulating an inner ring capacitance signal and an outer ring capacitance signal of the thin film capacitor respectively through independent and opposite-phase carrier signals, summing the modulated inner ring capacitance signal and the modulated outer ring capacitance signal to obtain a capacitance difference signal, and transmitting the capacitance difference signal to the first processor, wherein the first processor is used for calculating and processing the capacitance difference signal to obtain a vacuum degree detection result.

According to the detection circuit of the capacitive film vacuum gauge, provided by the invention, the capacitance detection module comprises a film capacitor, a digital-to-analog converter, a first operational amplifier, a second operational amplifier, an addition circuit and an analog-to-digital converter;

the digital-to-analog converter is used for outputting a first carrier signal and a second carrier signal, and the first carrier signal and the second carrier signal are independent and in opposite phase;

the first carrier signal and an inner ring capacitance signal of the thin film capacitor are input into a first operational amplifier, and are modulated and amplified by the first operational amplifier to output a first modulation signal;

the second carrier signal and the outer ring capacitance signal of the thin film capacitor are input into a second operational amplifier, and a second modulation signal is output after the second carrier signal and the outer ring capacitance signal of the thin film capacitor are modulated and amplified by the second operational amplifier;

the first modulation signal and the second modulation signal are input into the addition circuit, summed by the addition circuit and output to a capacitance difference signal, and the capacitance difference signal is subjected to analog-to-digital conversion by the analog-to-digital converter and input to the first processor.

According to the detection circuit of the capacitive thin film vacuum gauge, the capacitive test plate further comprises a first temperature sensor, the first temperature sensor is electrically connected with the first processor, and the first temperature sensor is used for collecting temperature information of the capacitive test plate.

The detection circuit of the capacitive film vacuum gauge further comprises a temperature control plate, wherein the temperature control plate is electrically connected with the capacitance test plate;

the temperature control board comprises a temperature control module, a second processor and a second power supply module, the temperature control module is electrically connected with the second processor, and the second power supply module is respectively electrically connected with the temperature control module and the second processor;

the temperature control module is used for collecting temperature information of the surrounding environment of the temperature control plate and transmitting the temperature information of the surrounding environment of the temperature control plate to the second processor, the second processor is used for analyzing and processing the temperature information of the surrounding environment of the temperature control plate to generate a temperature control instruction, and transmits the temperature control instruction to the temperature control module, and the temperature control module is further used for executing heating or stopping heating according to the temperature control instruction.

According to the detection circuit of the capacitive thin film vacuum gauge, the temperature control module comprises a thermistor and a heater, and the thermistor and the heater are both electrically connected with the second processor;

the thermistor is used for gathering the temperature information of the surrounding environment of the temperature control plate, and will the temperature information of the surrounding environment of the temperature control plate is transmitted to the second processor, the second processor is right the temperature information of the surrounding environment of the temperature control plate is analyzed and processed to generate a temperature control instruction, and the temperature control instruction is transmitted to the heater, and the heater is used for executing heating or stopping heating according to the temperature control instruction.

According to the detection circuit of the capacitive thin film vacuum gauge provided by the invention, the temperature control module further comprises a second temperature sensor, the second temperature sensor is electrically connected with the second processor, and the second temperature sensor is used for collecting temperature information of a temperature control plate and transmitting the temperature information of the temperature control plate to the second processor.

According to the detection circuit of the capacitive film vacuum gauge, the temperature control board further comprises a key module, the key module is electrically connected with the second processor, and the key module is used for receiving zero setting and fine tuning control trigger signals.

According to the detection circuit of the capacitive film vacuum gauge, the temperature control board further comprises an indicator light module, the indicator light module is electrically connected with the second processor, and the indicator light module is used for indicating the working states of the temperature control board and the capacitance test board.

In a second aspect, the present invention also provides a vacuum gauge comprising any one of the above capacitive thin film gauge detection circuits.

In a third aspect, the present invention also provides a vacuum degree detection method, including:

the inner ring capacitance signal and the outer ring capacitance signal of the film capacitor are respectively modulated through independent and opposite-phase carrier signals;

summing the modulated inner ring capacitance signal and the modulated outer ring capacitance signal to obtain a capacitance difference signal;

and calculating the capacitance difference signal to obtain a vacuum degree detection result.

According to the detection circuit, the vacuum gauge and the vacuum degree detection method of the capacitive film vacuum gauge, the inner ring capacitance signal and the outer ring capacitance signal of the film capacitor are respectively modulated through independent and opposite-phase carrier signals, the modulated inner ring capacitance signal and the modulated outer ring capacitance signal are summed to obtain a capacitance difference signal, and then a vacuum degree detection result is obtained through conversion.

Drawings

In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a detection circuit of a capacitive thin film vacuum gauge provided in the present invention;

FIG. 2 is a schematic diagram illustrating a detailed structure of the capacitive test board;

FIG. 3 is a schematic diagram of the power supply principle of the first power supply module;

FIG. 4 is a schematic structural diagram of a thermal control plate;

FIG. 5 is a schematic diagram of a detailed structure of a thermal control plate;

FIG. 6 is a schematic diagram of the power supply principle of the second power supply module;

FIG. 7 is a diagram illustrating the results of a stability test of the output air pressure of the detection circuit of the capacitive thin film gauge;

FIG. 8 is a graphical representation of the results of the scale factor tests of the test gauge and the standard gauge;

FIG. 9 is a graph showing the results of a linearity error test of a test gauge;

FIG. 10 is a schematic view of the structure of a vacuum gauge provided by the present invention;

FIG. 11 is a second schematic structural view of a vacuum gauge provided in the present invention;

FIG. 12 is a graph showing the measurement of the output of a vacuum gauge under absolute vacuum;

FIG. 13 is a graph showing the measurement results of the output of the vacuum gauge under the condition of 0.02 Torr;

FIG. 14 is a schematic flow chart of a vacuum level detection method according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Fig. 1 shows a detection circuit of a capacitive thin film vacuum gauge provided by an embodiment of the present invention, including: the capacitive test board 100 comprises a capacitive detection module 101, a first processor 102 and a first power supply module 103, wherein the capacitive detection module 101 is electrically connected with the first processor 102, and the first power supply module 103 is electrically connected with the capacitive detection module 101 and the first processor 102 respectively;

the capacitance detection module 101 is configured to modulate an inner ring capacitance signal and an outer ring capacitance signal of the thin film capacitor respectively through independent and inverted carrier signals, sum the modulated inner ring capacitance signal and the modulated outer ring capacitance signal to obtain a capacitance difference signal, and transmit the capacitance difference signal to the first processor 102, where the first processor 102 is configured to calculate and process the capacitance difference signal to obtain a vacuum degree detection result.

Specifically, referring to fig. 2, the capacitance detection module 101 includes a thin film capacitor 201, a digital-to-analog converter 202, a first operational amplifier 203, a second operational amplifier 204, an adder circuit 205, and an analog-to-digital converter 206;

the dac 202 is configured to output a first carrier signal ZBN and a second carrier signal ZBP, where the first carrier signal ZBN and the second carrier signal ZBP are independent and opposite in phase;

the first carrier signal and the inner ring capacitance signal of the thin film capacitor 201 are both input to the first operational amplifier 203, and are modulated and amplified by the first operational amplifier 203 to output a first modulation signal;

the second carrier signal and the outer ring capacitance signal of the thin film capacitor 201 are both input to the second operational amplifier 204, and are modulated and amplified by the second operational amplifier 204 to output a second modulation signal;

the first modulation signal and the second modulation signal are both input to the adder 205, summed by the adder 205 and output a capacitance difference signal, and the capacitance difference signal is analog-to-digital converted by the analog-to-digital converter 206 and input to the first processor 102.

In this embodiment, the digital-to-analog converter 202 is implemented by a 16-bit DAC, and ZBP and ZBN are two carrier signals output by the 16-bit DAC and used for modulating inner and outer ring capacitance signals of the film capacitor, summing the two signals after modulation, outputting the two signals to a differential input end of an external ADC (i.e., the analog-to-digital converter 206) through voltage following and phase inversion respectively, and implementing demodulation and filtering of the signals after the signals are acquired by the first processor 102.

Because the matching errors or consistency errors of the inner ring capacitor, the outer ring capacitor and the circuit parameters can be compensated by finely adjusting the amplitude (even the phase) of one path of carrier signal, the detection circuit is convenient to zero and has low requirements on the matching of hardware parameters.

According to the detection circuit, the two operational amplifiers are arranged, the static working point of the operational amplifier is set to be 0, the alternating current amplitude can be amplified to 3 times, the signal to noise ratio is improved, the noise is reduced, and the detection result is more stable and reliable. Because the two paths of carrier signals are independently loaded, when only one path of carrier signal is added and the amplitude of the other path of carrier signal is 0, the capacitance value of the corresponding electrode end of the film capacitor loaded with the wave signal can be accurately measured, and the matching error of the film capacitor can be compensated through the compensation capacitor.

Specifically, when a wave signal is loaded at the inner ring electrode end of the thin film capacitor, a capacitance value corresponding to the inner ring electrode end, namely an inner ring capacitance signal, can be obtained, and then when a wave signal is loaded at the outer ring electrode end of the thin film capacitor, a capacitance value corresponding to the outer ring electrode end, namely an outer ring capacitance signal, can be obtained, so that the difference between the capacitance value corresponding to the inner ring electrode end and the capacitance value corresponding to the outer ring electrode end is close to 0, and the zero setting operation can be realized, and the hardware zero setting process is more convenient.

More preferably, referring to fig. 2, the capacitive test board 100 further includes a first temperature sensor 207, the first temperature sensor 207 is electrically connected to the first processor 102, and the first temperature sensor 207 is configured to collect temperature information of the capacitive test board. In this embodiment, the first temperature sensor 207 is implemented by using a temperature measurement chip of the model LMT85, and the first processor 102 is implemented by using an ARM controller.

Referring to fig. 3, in this embodiment, the first power supply module 103 specifically includes:

the primary power supply unit is used for inputting source voltages of +15V and-15V;

the secondary power supply unit is used for reducing the source voltage of +15V and-15V through the low dropout linear regulators LDO3 and LDO4 and stabilizing the source voltage to the dual-power voltage of +12V and-12V, and the dual-power voltage is used for supplying power to the two operational amplifiers (or comparators);

the three-level power supply unit is used for reducing the +15V source voltage to 5.3V transition voltage through the low dropout regulator LDO1, and reducing the transition voltage to 5V secondary voltage through the LDO2, wherein the secondary voltage is used for supplying power to the first temperature sensor and also supplying power to the digital-to-analog converter;

and the four-stage power supply unit is used for reducing the secondary voltage of 5V to an analog power supply voltage of 3.3V, namely VA3.3 in fig. 3, through the power supply chip, and reducing the transition voltage of 5.3V to a digital power supply voltage of 3.3V, namely VD3.3 in fig. 3, wherein the analog power supply voltage is used for supplying power to the analog-to-digital converter (ADC), and the digital power supply voltage is mainly used for supplying power to the first processor.

In the exemplary embodiment, in consideration of the influence of the drift of the device itself with temperature in the detection circuit of the capacitance type thin film vacuum gauge on the measurement result, the present embodiment also provides a temperature control portion in the detection circuit. Referring to fig. 4, the detection circuit of the capacitive thin film gauge further includes a temperature control board 400, and the temperature control board 400 is electrically connected to the capacitive test board 100;

the temperature control board 400 comprises a temperature control module 401, a second processor 402 and a second power supply module 403, wherein the temperature control module 401 is electrically connected with the second processor 402, and the second power supply module 403 is respectively electrically connected with the temperature control module 401 and the second processor 402;

the temperature control module 401 is configured to collect temperature information of an environment around the temperature control board, transmit the temperature information of the environment around the temperature control board to the second processor 402, the second processor 402 is configured to analyze the temperature information of the environment around the temperature control board, generate a temperature control instruction, transmit the temperature control instruction to the temperature control module 401, and the temperature control module 401 is further configured to perform heating or stop heating according to the temperature control instruction.

As can be seen from the peripheral structure diagram of the capacitive test board 100 shown in fig. 2, the first processor 102 is connected to the thermal control board 400 through a flat cable, so as to transmit command information and data information between the two circuit boards.

Specifically, referring to fig. 5, the temperature control module 401 includes a thermistor 501 and a heater 502, and both the thermistor 501 and the heater 502 are electrically connected to the second processor 402;

the thermistor 501 is configured to acquire temperature information of an environment around the temperature control board, transmit the temperature information of the environment around the temperature control board to the second processor 402, the second processor 402 performs analysis processing on the temperature information of the environment around the temperature control board, generates a temperature control instruction, and transmits the temperature control instruction to the heater 502, and the heater 502 is configured to perform heating or stop heating according to the temperature control instruction.

In this embodiment, the heater 502 may be implemented by a heating wire, and the second processor 402 may be implemented by an ARM controller. And the heater part adopts the peripheral 16-bit DAC, can improve the control accuracy of temperature. The temperature acquisition part realized by the thermistor 501 adopts an 18-bit external ADC for improving the temperature acquisition precision.

Preferably, referring to fig. 5, the temperature control module 401 further includes a second temperature sensor 503, the second temperature sensor 503 is electrically connected to the second processor 402, and the second temperature sensor 503 is configured to collect temperature information of the temperature control board and transmit the temperature information of the temperature control board to the second processor 402.

In this embodiment, the second temperature sensor 503 may be implemented by a temperature measurement chip of model LMT 85.

Preferably, referring to fig. 5, the thermal control board 400 further includes a button module 504, the button module 504 is electrically connected to the second processor 402, and the button module 504 is configured to receive the zeroing and fine-tuning control trigger signal. In this embodiment, the key module 504 includes a plurality of function keys, such as a zeroing key, a fine tuning key, and a switch key, for enabling a user to perform basic operations such as zeroing, fine tuning, or turning on/off.

Preferably, referring to fig. 5, the thermal control board 400 further includes an indicator light module 505, the indicator light module 505 is electrically connected to the second processor 402, and the indicator light module 505 is used for indicating the operating status of the thermal control board and the capacitive test board. The indicator light module 505 may be configured with one or more indicator lights for indicating different operating states, such as a zeroing state, a trimming state, a power-on state, a fault state, and the like.

As can also be seen from fig. 5, the second processor 402 performs signal transmission with external devices through the DB15 connector, such as power supply signal transmission and data signal transmission. The serial port communication part of the temperature control board 400 mainly comprises two serial port modules USART1 and USART2, wherein USART1 is communicated with an upper computer, USART2 is communicated with the capacitive test board 100, and the two serial port modules mainly transmit data signals and related command signals. The vacuum degree detection result or the air pressure measurement result of the whole detection circuit can be output through the analog output module 506 on the temperature control board 400, and the measurement result of the air pressure (or the vacuum degree) can be converted into voltage to be output for the user to measure.

Referring to fig. 6, a power supply structure of the second power supply module 403 in the present embodiment is substantially the same as the first power supply module 103, and the second power supply module 403 specifically includes:

the primary power supply unit is used for inputting source voltages of +15V and-15V, and the source voltage of +15V can supply power to the heater;

a secondary power supply unit, configured to step down the +15V and-15V source voltages through the low dropout regulators LDO3 and LDO4 and regulate the source voltages to dual supply voltages of +12V and-12V, where the dual supply voltages are used to supply power to an operational amplifier, where the operational amplifier refers to an operational amplifier provided in the analog output module 506;

the three-level power supply unit is used for reducing the +15V source voltage to 5.3V transition voltage through the low dropout regulator LDO1, and reducing the transition voltage to 5V secondary voltage through the LDO2, wherein the secondary voltage is used for supplying power to a digital-to-analog converter (DAC) in the analog output module 506;

the four-stage power supply unit is used for reducing the secondary voltage of 5V to the digital power supply voltage of 3.3V, namely VD3.3 in fig. 6, and reducing the transition voltage of 5.3V to the analog power supply voltage of 3.3V, namely VA3.3 in fig. 6, wherein the analog power supply voltage is used for supplying power to the analog-to-digital converter ADC and the second temperature sensor, the analog-to-digital converter mainly refers to an analog-to-digital converter arranged between the second temperature sensor and the second processor, and the digital power supply voltage is mainly used for supplying power to the second processor, the serial port part, the key module and the indicator light module.

It is not difficult to discover, no matter be first power module or second power module in this embodiment, through the mode that steps down steady voltage and handle, can effectually reduce noise and undulant influence to capacitor detection part operational amplifier stability and noise on the power, avoided the influence of power noise to the detection performance.

Meanwhile, the voltage of 5V is generated, namely, the voltage of +15V is reduced to +5.3V and then reduced to +5V, the voltage reduction mode of directly reducing the voltage of +15V to +5V is replaced by the voltage reduction mode for two times, the power consumption is low, and the temperature of the circuit board can be effectively reduced.

It is easy to find that the detection circuit of the capacitive thin film vacuum gauge provided by the embodiment can accurately measure the capacitance values of the inner ring and the outer ring of the thin film capacitor, and the capacitance difference is obtained by summing the modulated capacitance values through the adder circuit, so that the common mode rejection ratio of the operational amplifier is not required, the function of vacuum degree detection can be realized by using a common operational amplifier, and meanwhile, the circuit is ensured to have better stability and higher linearity.

The detection circuit of the capacitive thin film vacuum gauge provided by the embodiment can quickly and conveniently realize the function of measuring the air pressure, and after the second processor collects the equivalent voltage signals output by the capacitive test board, the equivalent voltage signals are respectively subjected to digital demodulation and filtering, and finally the digital output of the air pressure is realized through a serial port, and the analog output can also be realized through an externally-hung 16-bit DAC. In order to verify the stability of the measurement result, the present embodiment performs a test on the detection circuit for 5 hours, and sets the stability index to 0.1mtorr, and the stability test result is shown in fig. 7, where the abscissa is time and the ordinate is the air pressure value, and it can be seen from fig. 7 that the air pressure output result of the detection circuit is relatively stable.

Meanwhile, the linearity test is also performed on the detection circuit in the embodiment, fig. 8 shows the scale factor test results of the test gauge (i.e. the detection circuit of the capacitive thin film vacuum gauge provided in the embodiment) and the standard gauge, wherein the fitted curve coincides with the measured curve, fig. 9 shows the linearity error test result of the test gauge, and it can be seen from the test results shown in fig. 8 and fig. 9 that the detection circuit has good linearity.

On the other hand, the embodiment of the invention also provides a vacuum gauge which comprises the detection circuit of the capacitance type film vacuum gauge and can realize the function of detecting the vacuum degree or the air pressure.

In an exemplary embodiment, the structure of the vacuum gauge may be the structure shown in fig. 10 and 11, referring to fig. 10, the vacuum gauge includes an adapter 1001 for mounting to an external device, an adapter clamp 1002, a sealing ring 1003, and a vacuum gauge body 1004, the adapter clamp 1002 fixes the adapter 1001 to the vacuum gauge body 1004 and seals the adapter 1001 by the sealing ring 1003, and the capacitive thin film vacuum gauge detection circuit is enclosed in the vacuum gauge body 1004. Specifically, in the present embodiment, the transfer joint 1001 is implemented by a KF16 joint.

Referring to fig. 11, a zeroing operation indicator 1101, a zeroing state indicator 1102, a temperature state indicator 1103 and a working state indicator 1104 are further disposed at the top of a vacuum gauge body 1004 of the vacuum gauge, wherein when the vacuum gauge is set to a zeroing state, the zeroing state indicator 1102 is turned on, the zeroing operation indicator 1101 is turned on when the zeroing operation is performed, the temperature state indicator 1103 is used for indicating whether the temperature is normal or not, and can be distinguished by lighting colors, for example, green indicates that the temperature is normal, red indicates that the temperature is abnormal, and the working state indicator 1104 can indicate information such as a startup state, a standby state, a fault state, and the like.

As can be seen from fig. 11, the vacuum gauge is further provided with a communication interface 1105, which may be a DB15 interface, and can connect the vacuum gauge with an external device to realize data transmission.

The vacuum gauge can be applied to a vacuum sintering furnace, the vacuum sintering furnace is used for carrying out protective sintering on a heated object in a high-temperature environment, one key test condition is required to be carried out in the vacuum environment, and the vacuum gauge can be applied to the vacuum sintering furnace for detecting the vacuum degree. The measuring range of the vacuum gauge provided by the embodiment is 0.01-0.1Torr, the working temperature is 45 ℃, the power is supplied by adopting +/-15V voltage, and the sintering furnace generally has zero setting and fine adjustment functions to keep the vacuum degree at about 0.02 Torr.

In the practical application process, taking an absolute vacuum application environment as an example, firstly, a product is powered in a vacuum environment, after a temperature state indicator lamp is turned on, the vacuum gauge is used for measuring, the current air pressure is absolute vacuum, so that the corresponding air pressure output is near 0Torr, the detection circuit adopts an analog output port, the output voltage range is 0-10V, and the corresponding air pressure range is 0.01-0.1 Torr. The corresponding air pressure output results in the absolute vacuum state are shown in fig. 12.

The degree of vacuum was then adjusted from absolute vacuum to 0.02Torr, the gauge pressure output was near 0.02Torr, and if there was a slight difference, the adjustment was made by the fine adjustment key, and the results of the pressure output at 0.02Torr are shown in FIG. 13. Therefore, the vacuum gauge can meet the actual air pressure measurement requirement.

In another aspect, referring to fig. 14, an embodiment of the present invention further provides a vacuum degree detection method, where the vacuum degree detection method uses the above-mentioned detection circuit of the thin film capacitance vacuum gauge to implement a vacuum degree detection function, and the method specifically includes:

step 1401: the inner ring capacitance signal and the outer ring capacitance signal of the film capacitor are respectively modulated through independent and opposite-phase carrier signals;

step 1402: summing the modulated inner ring capacitance signal and the modulated outer ring capacitance signal to obtain a capacitance difference signal;

step 1403: and calculating the capacitance difference signal to obtain a vacuum degree detection result.

Specifically, the step 1401 specifically includes:

firstly, acquiring a first carrier signal and a second carrier signal, wherein the first carrier signal and the second carrier signal are independent and in opposite phase;

then, modulating an inner ring capacitance signal of the film capacitor through a first carrier signal to obtain a first modulation signal;

and simultaneously, modulating the outer ring capacitance signal of the thin film capacitor through a second carrier signal to obtain a second modulation signal.

Correspondingly, the step 1402 specifically includes:

and summing the first modulation signal and the second modulation signal to obtain a capacitance difference signal.

In an exemplary embodiment, in the vacuum degree detection method, the temperature of the measuring device is also collected and regulated during the vacuum degree detection process, so that the vacuum degree detection process is safer and more reliable.

Therefore, in the vacuum degree detection method provided by this embodiment, after the inner ring capacitance signal and the outer ring capacitance signal of the thin film capacitor are respectively modulated by the independent and opposite-phase carrier signals, the capacitance difference can be obtained by summing, so that the performance requirement on the device used for implementing the method is not high, the stability of the vacuum degree detection process is ensured to be higher, and the obtained vacuum degree detection result is more stable and reliable.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.