CN117665397B - Capacitor complex impedance measurement method, circuit and device - Google Patents
Capacitor complex impedance measurement method, circuit and device Download PDFInfo
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Abstract
The invention belongs to the technical field of impedance measurement, and particularly relates to a capacitor complex impedance measurement method, circuit and device with self-adaptive parasitic capacitance compensation, wherein the method comprises the steps of inputting sinusoidal alternating current signal excitation into a measurement circuit, and carrying out output zeroing on the measurement circuit in an initial state so as to detect the complex impedance of a capacitor to be detected; shifting the phase of an input sinusoidal alternating current signal by 90 degrees or 0 degrees to generate a phase control signal after phase shifting; responding to the phase control signal and carrying out phase control rectification on the alternating current signal, filtering the alternating current signal subjected to phase control rectification, and converting the alternating current signal into direct current voltage for output; the measuring circuit provided by the invention can be used for measuring the complex impedance of the capacitive sensor, can also be used for measuring the variation of the complex impedance of the capacitive sensor, can automatically eliminate parasitic capacitance, achieves the purpose of precision measurement, and has the characteristics of large measuring range, high measuring precision and strong anti-interference capability.
Description
Technical Field
The invention belongs to the technical field of impedance measurement, and particularly relates to a capacitor complex impedance measurement method, a circuit and a device.
Background
The micro capacitance measurement technology is widely applied to various MEMS devices, capacitance sensors and inter-structure distributed capacitance all the time, so that the micro capacitance measurement technology can be applied to relevant application fields such as military manufacturing, aerospace, vacuum measurement, biomedicine and the like. For the application scenes of the capacitive sensor such as the capacitive tomography, under alternating current excitation, the measurement of the complex impedance of the capacitor can obtain imaging images with higher resolution or more target characteristic information.
At present, many measuring circuits are invented based on the measuring methods such as resonance method, CV conversion, charge and discharge, etc., but the complex impedance of the capacitor is tested. Meanwhile, parasitic capacitance or stray capacitance exists, the generation of the parasitic capacitance can be reduced through board-level design optimization, measures such as signal shielding of input and output ends are generally adopted, and the parasitic capacitance can also be reduced through circuit scheme design optimization, and a circuit with differential output is generally designed, so that common-mode signals can be eliminated easily. However, not all the detection circuits adopt differential output, so that the scheme for designing the differential output circuit to eliminate parasitic capacitance has a certain limitation, so that the parasitic capacitance is difficult to eliminate in the measurement means. This also causes the measured capacitance to be larger than the theoretical calculation or simulation, resulting in a reduced resolution of the capacitance tomography. In addition, there are increasing demands on the cost, sensitivity, parasitic effect suppression, etc. of the measurement circuit.
Disclosure of Invention
The invention aims to provide a method, a circuit and a device for measuring complex impedance of a capacitor, which are used for solving the problems in the background technology.
The invention realizes the above purpose through the following technical scheme:
In a first aspect, the present invention provides a method of measuring complex impedance of a capacitor, suitable for use in a measurement circuit comprising a capacitor to be detected, the method comprising:
Inputting sinusoidal alternating current signal excitation into the measuring circuit, and carrying out output zeroing on the measuring circuit in an initial state so as to detect the complex impedance of the capacitor to be detected;
shifting the phase of an input sinusoidal alternating current signal by 90 degrees or 0 degrees to generate a phase control signal after phase shifting;
and responding to the phase control signal and carrying out phase control rectification on the alternating current signal, filtering the alternating current signal subjected to phase control rectification, and converting the alternating current signal into direct current voltage for output.
As a further optimization scheme of the invention, the initial state comprises the initial moment when the measuring circuit is not connected to the capacitor to be detected or the measuring circuit is connected to the capacitor to be detected for power-up.
As a further optimization scheme of the invention, based on the real part and the imaginary part of the capacitor complex number to be detected, when the real part is detected correspondingly, the phase of the input sinusoidal alternating current signal is shifted by 90 degrees, and when the imaginary part is detected correspondingly, the phase of the input sinusoidal alternating current signal is shifted by 0 degree.
In a second aspect, the present invention provides a capacitor complex impedance measurement circuit for implementing the measurement method as described above, the measurement circuit comprising a self-compensating calibration bridge circuit, a phase-shifting circuit and a phase-controlled rectifying circuit;
The self-compensating calibration bridge circuit is used for inputting sinusoidal alternating current signal excitation into the measuring circuit, and outputting zero setting is carried out on the measuring circuit at the initial moment when the self-compensating calibration bridge circuit is not connected with the capacitor to be detected or the self-compensating calibration bridge circuit is connected with the capacitor to be detected for power-up so as to detect the complex impedance of the capacitor to be detected;
The phase shifting circuit is used for shifting the phase of an input sinusoidal alternating current signal by 90 degrees or 0 degrees to generate a phase-controlled signal after phase shifting;
The phase control rectification circuit is used for responding to the phase control signal and carrying out phase control rectification on the alternating current signal, filtering the alternating current signal subjected to phase control rectification, and converting the alternating current signal into direct current voltage for output.
As a further optimization scheme of the invention, the self-compensation calibration bridge circuit comprises a first-stage reverse proportional circuit, an integrating circuit and a feedback circuit with PI regulation;
The phase control rectification circuit comprises a comparator, a second-stage reverse proportion circuit, an analog switch S1 and a second-order low-pass filter circuit; the comparator being an operational amplifier The operational amplifier/>The reverse input end of the (E) is connected with the phase shifting circuit, the forward input end is electrically connected with the ground, and the operational amplifier/>The output end of the switch S1 is connected with the signal output end of the analog switch S1, the signal output end of the switch S1 is connected with the second-order low-pass filter circuit, and the signal is/>Two input ends of the analog switch S1 are respectively connected to the integrating circuit of the self-compensating calibration bridge circuit and the output end of the second-stage inverse proportion circuit;
the first-stage reverse proportional circuit routing amplifier Resistance/>、/> Composition, resistance/>Is connected to electrical ground at one end and an amplifier/>Is connected to the positive input terminal of the amplifier/>Inverting input terminal and resistance/>、/>Connected, resistance/>Connected with the capacitor to be detected in the integrating circuit, and the resistor/>At the other end of the amplifier/>Is connected with the output end of the power supply;
the integrating circuit is composed of an operational amplifier Feedback resistance/>Composition, amplifier/>And resistance/>The first-stage reverse proportional circuit and the reference capacitor/>, are formedIn series connection with the capacitor to be detected and the automatic compensation capacitor/>In parallel, and pass through an operational amplifier/>And feedback resistance/>Form the output signal of the integrating circuit/>；
The second-stage reverse proportion circuit consists of an amplifierAnd resistance/>、/>Composition, output end and resistance of the integration circuit/>One end is connected with the resistor/>And amplifier/>Reverse input terminal and resistance/>Connected, resistance/>The other end is connected with an amplifier/>Is connected to the output of the amplifier/>Is connected to electrical ground, the output signal of the second stage reverse scaling circuit, i.e. amplifier/>The output signal at the output end of (2) is/>The self-compensating capacitance/>Programmable capacitance, capacitor to be detected including leakage capacitance/>And leakage resistance/>；
The feedback circuit with PI regulation comprises an FPGA single chip microcomputer system, an ADC acquisition circuit and a PI controller, wherein the ADC acquisition circuit is connected with the output end of the second-order low-pass filter circuit, after the ADC acquisition circuit collects information, the information is transmitted into the single chip microcomputer system and then transmitted into the PC end, the PC end realizes the calibration of a variable capacitor CT through the PI controller, and according to the output feedback of a phase control rectifying circuit based on a comparator, the ADC acquires a PI regulation value of a system output signal through the MCU controller, and the zero setting of a capacitor to be detected or a system in an initial power-on state is completed without access detection.
As a further optimized scheme of the invention, in the phase shifting circuit, when the imaginary part of the capacitor to be detected is detectedThe phase-shifting circuit is a differential circuit when detecting the real part/>, of the capacitive sensorAt this time, no phase shift is required, and the alternating current signal and the operational amplifier/>, which is the next stageIs connected to the inverting input terminal of (c).
As a further optimization scheme of the invention, a normally open contact of the analog switch S1 is connected to the output end of the self-compensating calibration bridge circuitNormally closed contacts are connected to the output terminals/>When the input end shifts the phase of the original excitation signal by 90 degrees, the analog switch outputs a signal/>The DC power is integrated by a second-order low-pass filter circuit, and the imaginary part/>, of the capacitor to be detected is detected at the moment; When the input end is the original excitation signal, the real part/>, of the capacitor to be detected is detectedWherein the input sinusoidal excitation signal isA is the gain of the input sinusoidal excitation signal;
Wherein, when detecting When the phase of the output signal of the phase shifting circuit is lagged by 90 degrees for the excitation signal, and then the analog switch/>, which is controlled by the comparator, is used forThe output signal is:
integrating by a second-order low-pass filter circuit, and obtaining a direct current signal when the cut-off frequency of the second-order low-pass filter is far smaller than the frequency of the excitation signal The output DC quantity after signal integration in one period is approximately calculated as:
Detecting imaginary part The method comprises the following steps:
When detecting When the phase-shifting circuit is not needed, the excitation signal directly passes through the analog switch/>, which is controlled by the comparatorThe output signal is:
Detecting real part The method comprises the following steps:
。
In a third aspect, the invention provides a measurement device comprising measurement circuitry in any of the possible implementations of the first or second aspects.
1. The invention has the beneficial effects that:
The measuring circuit provided by the invention can be used for measuring the complex impedance of the capacitive sensor, can also be used for measuring the variation of the complex impedance of the capacitive sensor, can automatically eliminate parasitic capacitance, achieves the purpose of precision measurement, and has the characteristics of large measuring range, high measuring precision and strong anti-interference capability.
2. The measuring circuit provided by the invention comprises a self-compensating calibration bridge circuit, a phase shifting circuit and a phase control rectifying circuit based on a comparator, realizes the conversion of complex impedance (or leakage capacitance and leakage resistance) of the capacitive sensor into direct-current voltage for detection, can be used for measuring the complex impedance of the capacitive sensor, can also be used for measuring the variation of the complex impedance of the capacitive sensor, can automatically eliminate parasitic capacitance and achieves the purpose of precision measurement.
Drawings
FIG. 1 is a flow chart illustrating the measurement method according to the present invention.
Fig. 2 is a system schematic block diagram of the present invention.
Fig. 3 is a schematic block diagram of a programmable capacitor of the present invention.
Fig. 4 is a circuit diagram for realizing 90 ° phase shift of an input ac signal in the phase shift circuit of the present invention.
Detailed Description
The present application will be described in further detail with reference to the accompanying drawings, wherein it is to be understood that the following detailed description is for the purpose of further illustrating the application only and is not to be construed as limiting the scope of the application, as various insubstantial modifications and adaptations of the application to those skilled in the art can be made in light of the foregoing disclosure.
Example 1
As shown in fig. 1, the present embodiment provides a method for measuring complex impedance of a capacitor, which is suitable for a measurement circuit including a capacitor to be detected, and includes:
S1, inputting sinusoidal alternating current signal excitation into the measurement circuit, converting the detected complex impedance of the capacitive sensor into a voltage signal under the condition of inputting sinusoidal alternating current signal excitation, and outputting zero setting to the measurement circuit under an initial state so as to detect the complex impedance of a capacitor to be detected; parasitic capacitance can be automatically eliminated by the system zeroing operation.
Specifically, the initial state includes an initial time when the measuring circuit is not connected to the capacitor to be detected or the measuring circuit is connected to the capacitor to be detected for power-up.
S2, shifting the phase of an input sinusoidal alternating current signal by 90 degrees or 0 degrees to generate a phase control signal after phase shifting;
Specifically, based on the real part and the imaginary part of the complex number of the capacitor to be detected, when the real part is detected correspondingly, 90 degrees of phase shift is performed on the input sinusoidal alternating current signal, and when the imaginary part is detected correspondingly, 0 degree of phase shift is performed on the input sinusoidal alternating current signal, namely, phase shift is not needed.
And S3, responding to the phase control signal and carrying out phase control rectification on the alternating current signal, filtering the alternating current signal subjected to phase control rectification, and converting the filtered alternating current signal into direct current voltage for output. Wherein the filtering operation is based on a low pass filtering circuit implementation.
It will be appreciated that the above measurement method is applicable to sensors based on capacitive complex impedance or complex impedance variation measurements; the complex impedance (or leakage capacitance and leakage resistance) of the capacitive sensor is converted into direct-current voltage for detection, and the method can be used for measuring the complex impedance of the capacitive sensor, can also only measure the variation of the complex impedance of the capacitive sensor, can automatically eliminate parasitic capacitance and achieves the purpose of precision measurement.
Example 2
Based on the same inventive concept, a measurement circuit corresponding to the measurement method is also provided in this embodiment, and since the principle of solving the problem of the measurement circuit in the embodiment of the present disclosure is similar to that of the measurement method in the embodiment of the present disclosure, the implementation of the measurement circuit may refer to the implementation of the method, and the repetition is omitted.
As shown in fig. 2-4, the present embodiment provides a capacitor complex impedance measurement circuit for implementing the measurement method as above, the measurement circuit including a self-compensating calibration bridge circuit, a phase shift circuit, and a phase control rectifier circuit;
the self-compensating calibration bridge circuit is used for inputting sinusoidal alternating current signal excitation into the measuring circuit, and outputting zero setting is carried out on the measuring circuit at the initial moment when the self-compensating calibration bridge circuit is not connected with the capacitor to be detected or the self-compensating calibration bridge circuit is connected with the capacitor to be detected for power-on so as to detect the complex impedance of the capacitor to be detected;
the phase shifting circuit is used for shifting the phase of an input sinusoidal alternating current signal by 90 degrees or 0 degrees to generate a phase control signal after phase shifting;
the phase control rectification circuit is used for responding to the phase control signal and carrying out phase control rectification on the alternating current signal, and the alternating current signal after the phase control rectification is filtered and then converted into direct current voltage to be output.
Referring specifically to fig. 2, as a further implementation, the self-compensating calibration bridge circuit includes a first stage inverse proportional circuit, an integrating circuit, and a feedback circuit with PI regulation;
The phase control rectification circuit comprises a comparator, a second-stage reverse proportion circuit, an analog switch S1 and a second-order low-pass filter circuit; comparator, i.e. operational amplifier Operational amplifier/>The reverse input end of the (E) is connected with the phase shifting circuit, the forward input end is electrically connected with the ground, and the operational amplifier/>The output end of the switch S1 is connected with the signal output end of the analog switch S1, the signal output end of the switch S1 is connected with the second-order low-pass filter circuit, and the signal is/>The integrating circuit of the self-compensating calibration bridge circuit, to which the two input ends of the analog switch S1 are respectively connected, is connected with the output end of the second-stage inverse proportional circuit;
First-stage reverse proportional circuit routing amplifier Resistance/>、/>、/>Composition, resistance/>Is connected to electrical ground at one end and an amplifier/>Is connected to the positive input terminal of the amplifier/>Inverting input terminal and resistance/>、/>Connected to a resistorConnected with a capacitor to be detected in an integrating circuit, and the resistor/>At the other end of the amplifier/>Is connected with the output end of the power supply;
integrating circuit with operational amplifier And feedback resistance/>Composition, amplifier/>And resistance/>、/>、/>The first-stage reverse proportional circuit and the reference capacitor/>, are formedIn series connection with the capacitor to be detected and the automatic compensation capacitor/>In parallel, and pass through an operational amplifier/>And feedback resistance/>Form the output signal of the integrating circuit/>；
The second-stage reverse proportional circuit is composed of an amplifierAnd resistance/>、/>The output end of the integrating circuit and the resistor/>, are formedOne end is connected with the resistor/>And amplifier/>Reverse input terminal and resistance/>Connected, resistance/>The other end is connected with an amplifier/>Is connected to the output of the amplifier/>Is connected to electrical ground, the output signal of the second stage reverse scaling circuit, i.e. amplifier/>The output signal at the output end of (2) is/>Automatic compensation capacitor/>For programmable capacitance, the capacitor to be detected includes leakage capacitance/>And leakage resistance/>。
The feedback circuit with PI regulation comprises an FPGA single-chip microcomputer system, an ADC acquisition circuit and a PI controller, wherein the ADC acquisition circuit is connected with the output end of the second-order low-pass filter circuit, after the ADC acquisition circuit collects information, the information is transmitted into the single-chip microcomputer system and then transmitted into the PC end, the PC end realizes the calibration of the variable capacitor CT through the PI controller, and according to the output feedback of the phase control rectifying circuit based on the comparator, the ADC acquires the PI regulation value of the system output signal through the MCU controller, and the zero setting under the initial state of the power-on of the system or the capacitor to be detected which is not connected in detection is completed.
Referring to fig. 2, the measurement circuit further includes: FPGA singlechip system, ADC acquisition circuit, PI controller.
According to the output feedback of a phase control rectifying circuit based on a comparator, an ADC (analog-to-digital converter) collects and then carries out PI (proportion integration) adjustment on a system output signal through an MCU (micro control Unit)The value is zeroed under the initial state of power-on of a capacitor to be detected without access detection or a system, and the input of the integrating circuit passes through an amplifier/>And resistance/>、/>、/>A first-stage reverse proportional circuit is formed;
wherein when the input sinusoidal excitation is Integrating circuit output/>, of the self-compensating calibration bridge circuitAnd the integrating circuit outputs a signal/>, through a second-stage reverse proportional circuitThe method comprises the following steps:
in the method, in the process of the invention, Is the gain of the inverse proportional circuit,/>Is the gain of the input sinusoidal excitation signal.
The ADC acquisition circuit is connected with the output end of the low-pass filter LPF, and after the information is collected by the ADC acquisition circuit, the information is transmitted into the singlechip system, and after simple processing, the information is transmitted into the PC end, and the PC end realizes the calibration of the variable capacitor CT through the PI controller. When the capacitor sensor is not connected in the initial state, initialization zeroing is carried out, thus self-adaption capacitor supplementing can be carried out, and parasitic capacitance influence is eliminated; when the capacitor sensor is connected in an initial state, initialization zeroing is performed, at the moment, the influence of parasitic capacitance is eliminated to perform self-adaptive parasitic capacitance supplement, and the change quantity of the capacitor sensor can be directly detected, wherein the change quantity comprises the change quantity of an imaginary part (leakage capacitance) of the capacitor sensor and the change quantity of a real part (leakage resistance) of the capacitor sensor.
As a further implementation, in the phase shift circuit, when detecting the imaginary part of the capacitor to be detectedThe phase-shifting circuit is a differential circuit when detecting the real part/>, of the capacitive sensorAt this time, no phase shift is required, and the alternating current signal and the operational amplifier/>, which is the next stageIs connected to the inverting input terminal of (c).
As a further implementation, based on the above measurement circuit, automatic elimination of parasitic capacitance is achieved by implementation of the following steps:
(1) Control of analog switches by comparison of the input of a phase shifter with ground For phase control of signals, the normally open contact of the analog switch S1 is connected to the output end/>, of the self-compensating calibration bridge circuitNormally closed contacts are connected to the output terminals/>When the input end shifts the phase of the original excitation signal by 90 degrees, the analog switch outputs a signal/>The DC power is integrated by a second-order low-pass filter circuit, and the imaginary part/>, of the capacitor to be detected is detected at the moment; When the input end is the original excitation signal, the real part/>, of the capacitor to be detected is detected; Wherein the input sinusoidal excitation signal is/>A is the gain of the input sinusoidal excitation signal;
Wherein, when detecting When the phase of the output signal of the phase shifting circuit is lagged by 90 degrees for the excitation signal, and then the analog switch/>, which is controlled by the comparator, is used forThe output signal is:
(2) Integrating by a second-order low-pass filter circuit, and obtaining a direct current signal when the cut-off frequency of the second-order low-pass filter is far smaller than the frequency of the excitation signal The output DC quantity after signal integration in one period is approximately calculated as:
Detecting imaginary part The method comprises the following steps:
When detecting When the phase-shifting circuit is not needed, the excitation signal directly passes through the analog switch/>, which is controlled by the comparatorThe output signal is:
(3) Integrating by a second-order low-pass filter circuit, and obtaining a direct current signal when the cut-off frequency of the second-order low-pass filter is far smaller than the frequency of the excitation signal The output DC quantity after signal integration in one period is approximately calculated as:
‘
Detecting real part The method comprises the following steps:
。
Example 3
The present embodiment provides a measuring device comprising a measuring circuit as described above. For a specific description of the measuring device reference is made to the description of the measuring circuit described above, which is not described in detail here.
It will be appreciated that the other elements included in the measuring device are not limiting embodiments of the application.
The measuring device is a chip, a sensor, or an electronic device, or an internet of things device, etc., which are not listed here.
The above embodiments may be implemented in whole or in part by software, hardware, firmware, or any other combination. When implemented in software, the above-described embodiments may be implemented in whole or in part in the form of a computer program product. The computer program product comprises one or more computer instructions or computer programs. When the computer instructions or computer program are loaded or executed on a computer, the processes or functions described in accordance with embodiments of the present invention are produced in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable devices. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be transmitted from one website site, computer, server, or data center to another website site, computer, server, or data center by wired (e.g., infrared, wireless, microwave, etc.). The computer readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. that contains one or more sets of available media. The usable medium may be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium. The semiconductor medium may be a solid state disk.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
In addition, each functional module in the embodiments of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit.
The functions, if implemented in the form of software functional modules and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on such understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method described in the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a read-only memory (ROM), a random access memory (random access memory, RAM), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the application has been described in detail with reference to the foregoing embodiments, it will be appreciated by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not drive the essence of the corresponding technical solutions to depart from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims (4)
1. A method of measuring the complex impedance of a capacitor, suitable for use in a measurement circuit comprising a capacitor to be tested, the measurement circuit comprising a self-compensating calibration bridge circuit, a phase-shifting circuit and a phase-controlled rectifier circuit, the method comprising:
Inputting sinusoidal alternating current signal excitation into the measuring circuit, and carrying out output zeroing on the measuring circuit in an initial state so as to detect the complex impedance of the capacitor to be detected;
shifting the phase of an input sinusoidal alternating current signal by 90 degrees or 0 degrees to generate a phase control signal after phase shifting;
Responding to the phase control signal and carrying out phase control rectification on the alternating current signal, filtering the alternating current signal subjected to phase control rectification, and converting the alternating current signal into direct current voltage for output;
Based on the real part and the imaginary part of the capacitor complex number to be detected, the phase of the input sinusoidal alternating current signal is shifted by 90 degrees when the real part is detected correspondingly, and the phase of the input sinusoidal alternating current signal is shifted by 0 degree when the imaginary part is detected correspondingly;
The self-compensating calibration bridge circuit comprises a first-stage reverse proportional circuit, an integrating circuit and a feedback circuit with PI regulation;
The phase control rectification circuit comprises a comparator, a second-stage reverse proportion circuit, an analog switch S1 and a second-order low-pass filter circuit; the comparator being an operational amplifier The operational amplifier/>The reverse input end of the (E) is connected with the phase shifting circuit, the forward input end is electrically connected with the ground, and the operational amplifier/>The output end of the switch S1 is connected with the signal output end of the analog switch S1, the signal output end of the switch S1 is connected with the second-order low-pass filter circuit, and the signal is/>Two input ends of the analog switch S1 are respectively connected to the integrating circuit of the self-compensating calibration bridge circuit and the output end of the second-stage inverse proportion circuit;
the first-stage reverse proportional circuit routing amplifier Resistance/>、/>、/>Composition, resistance/>Is connected to electrical ground at one end and an amplifier/>Is connected to the positive input terminal of the amplifier/>Inverting input terminal and resistance/>、/>Connected to a resistorConnected with the capacitor to be detected in the integrating circuit, and the resistor/>At the other end of the amplifier/>Is connected with the output end of the power supply;
the integrating circuit is composed of an operational amplifier And feedback resistance/>Composition, amplifier/>And resistance/>The first-stage reverse proportional circuit and the reference capacitor/>, are formedIn series connection with the capacitor to be detected and the automatic compensation capacitor/>In parallel, and pass through an operational amplifier/>And feedback resistance/>Form the output signal of the integrating circuit/>；
The second-stage reverse proportion circuit consists of an amplifierAnd resistance/>、/>Composition, output end and resistance of the integration circuit/>One end is connected with the resistor/>And amplifier/>Reverse input terminal and resistance/>Connected, resistance/>The other end is connected with an amplifier/>Is connected to the output of the amplifier/>Is connected to electrical ground, the output signal of the second stage reverse scaling circuit, i.e. amplifier/>The output signal at the output end of (2) is/>The self-compensating capacitance/>For programmable capacitance, the capacitor to be detected includes leakage capacitance/>And leakage resistance/>；
The feedback circuit with PI regulation comprises an FPGA single chip microcomputer system, an ADC acquisition circuit and a PI controller, wherein the ADC acquisition circuit is connected with the output end of the second-order low-pass filter circuit, after the ADC acquisition circuit collects information, the information is transmitted into the single chip microcomputer system and then transmitted into a PC end, the PC end realizes the calibration of a variable capacitor CT through the PI controller, and according to the output feedback of a phase control rectifying circuit based on a comparator, the ADC acquires a PI regulation value of a system output signal through the MCU controller, and zero setting under the initial state of the power-on of a capacitor to be detected or the system is completed without access detection;
in the phase shifting circuit, when the imaginary part of the capacitor to be detected is detected The phase-shifting circuit is a differential circuit when detecting the real part/>, of the capacitive sensorAt this time, no phase shift is required, and the alternating current signal and the operational amplifier/>, which is the next stageIs connected with the inverting input terminal of the circuit;
The normally open contact of the analog switch S1 is connected to the output end of the self-compensating calibration bridge circuit Normally closed contacts are connected to the output terminals/>When the input end shifts the phase of the original excitation signal by 90 degrees, the analog switch outputs a signal/>The DC power is integrated by a second-order low-pass filter circuit, and the imaginary part/>, of the capacitor to be detected is detected at the moment; When the input end is the original excitation signal, the real part/>, of the capacitor to be detected is detected; Wherein the input sinusoidal excitation signal is/>A is the gain of the input sinusoidal excitation signal;
Wherein, when detecting When the phase of the output signal of the phase shifting circuit is lagged by 90 degrees for the excitation signal, and then the analog switch/>, which is controlled by the comparator, is used forThe output signal is:
integrating by a second-order low-pass filter circuit, and obtaining a direct current signal when the cut-off frequency of the second-order low-pass filter is far smaller than the frequency of the excitation signal The output DC quantity after signal integration in one period is approximately calculated as:
Detecting imaginary part The method comprises the following steps:
When detecting When the phase-shifting circuit is not needed, the excitation signal directly passes through the analog switch/>, which is controlled by the comparatorThe output signal is:
integrating by a second-order low-pass filter circuit, and obtaining a direct current signal when the cut-off frequency of the second-order low-pass filter is far smaller than the frequency of the excitation signal The output DC quantity after signal integration in one period is approximately calculated as:
Detecting real part The method comprises the following steps:
。
2. A method of measuring complex impedance of a capacitor as claimed in claim 1, wherein the initial state comprises an initial time when the measuring circuit is not connected to the capacitor to be detected or when the measuring circuit is connected to the capacitor to be detected.
3. A capacitor complex impedance measurement circuit for implementing the measurement method of claim 1, wherein the measurement circuit comprises a self-compensating calibration bridge circuit, a phase-shifting circuit, and a phase-controlled rectifier circuit;
The self-compensating calibration bridge circuit is used for inputting sinusoidal alternating current signal excitation into the measuring circuit, and outputting zero setting is carried out on the measuring circuit at the initial moment when the self-compensating calibration bridge circuit is not connected with the capacitor to be detected or the self-compensating calibration bridge circuit is connected with the capacitor to be detected for power-up so as to detect the complex impedance of the capacitor to be detected;
The phase shifting circuit is used for shifting the phase of an input sinusoidal alternating current signal by 90 degrees or 0 degrees to generate a phase-controlled signal after phase shifting;
The phase control rectification circuit is used for responding to the phase control signal and carrying out phase control rectification on the alternating current signal, filtering the alternating current signal subjected to phase control rectification, and converting the filtered alternating current signal into direct current voltage for output;
The self-compensating calibration bridge circuit comprises a first-stage reverse proportional circuit, an integrating circuit and a feedback circuit with PI regulation;
The phase control rectification circuit comprises a comparator, a second-stage reverse proportion circuit, an analog switch S1 and a second-order low-pass filter circuit; the comparator being an operational amplifier The operational amplifier/>The reverse input end of the (E) is connected with the phase shifting circuit, the forward input end is electrically connected with the ground, and the operational amplifier/>The output end of the switch S1 is connected with the signal output end of the analog switch S1, the signal output end of the switch S1 is connected with the second-order low-pass filter circuit, and the signal is/>Two input ends of the analog switch S1 are respectively connected to the integrating circuit of the self-compensating calibration bridge circuit and the output end of the second-stage inverse proportion circuit;
the first-stage reverse proportional circuit routing amplifier Resistance/>、/>、/>Composition, resistance/>Is connected to electrical ground at one end and an amplifier/>Is connected to the positive input terminal of the amplifier/>Inverting input terminal and resistance/>、/>Connected to a resistorConnected with the capacitor to be detected in the integrating circuit, and the resistor/>At the other end of the amplifier/>Is connected with the output end of the power supply;
the integrating circuit is composed of an operational amplifier And feedback resistance/>Composition, amplifier/>And resistance/>The first-stage reverse proportional circuit and the reference capacitor/>, are formedIn series connection with the capacitor to be detected and the automatic compensation capacitor/>In parallel, and pass through an operational amplifier/>And feedback resistance/>Form the output signal of the integrating circuit/>；
The second-stage reverse proportion circuit consists of an amplifierAnd resistance/>、/>The output end of the integrating circuit is connected with a resistorOne end is connected with the resistor/>And amplifier/>Reverse input terminal and resistance/>Connected, resistance/>The other end is connected with an amplifier/>Is connected to the output of the amplifier/>Is connected to electrical ground, the output signal of the second stage reverse scaling circuit, i.e. amplifier/>The output signal at the output end of (2) is/>The self-compensating capacitance/>For programmable capacitance, the capacitor to be detected includes leakage capacitance/>And leakage resistance/>；
The feedback circuit with PI regulation comprises an FPGA single chip microcomputer system, an ADC acquisition circuit and a PI controller, wherein the ADC acquisition circuit is connected with the output end of the second-order low-pass filter circuit, after the ADC acquisition circuit collects information, the information is transmitted into the single chip microcomputer system and then transmitted into a PC end, the PC end realizes the calibration of a variable capacitor CT through the PI controller, and according to the output feedback of a phase control rectifying circuit based on a comparator, the ADC acquires a PI regulation value of a system output signal through the MCU controller, and zero setting under the initial state of the power-on of a capacitor to be detected or the system is completed without access detection;
in the phase shifting circuit, when the imaginary part of the capacitor to be detected is detected The phase-shifting circuit is a differential circuit when detecting the real part/>, of the capacitive sensorAt this time, no phase shift is required, and the alternating current signal and the operational amplifier/>, which is the next stageIs connected to the inverting input terminal of (c).
4. A measuring device comprising a measuring circuit as claimed in claim 3.
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