CN117665397A - Capacitor complex impedance measurement method, circuit and device with self-adaptive parasitic capacitance compensation - Google Patents
Capacitor complex impedance measurement method, circuit and device with self-adaptive parasitic capacitance compensation 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, circuit and device with self-adaptive parasitic capacitance compensation.
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 use differential output, so the scheme of designing differential output circuits to eliminate parasitic capacitance has certain limitations that make it difficult to eliminate in these 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 capacitor complex impedance measuring method, a circuit and a device with self-adaptive parasitic capacitance compensation, so as to solve 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 for measuring complex impedance of a capacitor with adaptive parasitic capacitance compensation, suitable for 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 with adaptive parasitic capacitance compensation for implementing a measurement method as described above, the measurement circuit comprising 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 alternating current signal into direct current voltage for output.
As a further optimized scheme of the invention, the self-compensating calibration bridge circuit comprises a first-stage reverse proportional circuit, an integrating circuit, a second-stage reverse proportional circuit and a bandPIA regulated feedback circuit; wherein,
amplifierAnd resistance->The first-stage reverse proportional circuit and the reference capacitor are formed>Series connection with the capacitor to be detected and the automatic compensation capacitor +.>Parallel connection and pass through an operational amplifier>And feedback resistance->Composing the output signal of the integrating circuit>The integrating circuit is then passed through an amplifier +.>And resistance->The second-stage reverse proportional circuit is composed of the output signals +.>The automatic compensation capacitor->For programmable capacitance, the capacitor to be detected comprises leakage capacitance +.>And leakage resistance->。
As a further optimized scheme of the invention, the phase control rectifying circuit comprises a comparator, a reverse proportion circuit and an analog switchS1A second-order low-pass filter circuit; operational amplifierThe reverse input end of the phase shifting circuit is connected with the phase shifting circuit, and the forward input end is connected with the ground.
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 sensor>At this time, no phase shift is required, and the AC signal and the operational amplifier of the next stage are +.>Is connected to the inverting input terminal of (c).
As a further optimization scheme of the invention, the switch is simulatedS1Is connected to the output end of the self-compensating calibration bridge circuitThe normally closed contact is connected to the output terminal>When the input end shifts 90 degrees for the original excitation signal, the analog switch outputs 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>The method comprises the steps of carrying out a first treatment on the surface of the When the input terminal is the original excitation signal, the real part of the capacitor to be detected is detected>；
Wherein, when detectingWhen the phase of the output signal of the phase shifting circuit is 90 degrees behind the excitation signal, and then the analog switch is controlled by the comparator>The 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 signalThe output direct current after signal integration in one period can be approximately calculated as:
；
detecting imaginary partThe method comprises the following steps:
；
when detectingWhen the analog switch is in use, a phase shift circuit is not needed, and the excitation signal directly passes through the analog switch controlled by the comparator>The 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 signalThe output direct current after signal integration in one period can be approximately calculated as:
；
detecting real partThe method comprises the following steps:
。
in a third aspect, the invention provides a measurement device comprising the measurement circuit of the second aspect or any one of the possible implementations of the second aspect.
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.
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 following detailed description of the present application is provided in conjunction with the accompanying drawings, and it is to be understood that the following detailed description is merely illustrative of the application and is not to be construed as limiting the scope of the application, since numerous insubstantial modifications and adaptations of the application will be to those skilled in the art in light of the foregoing disclosure.
Example 1
As shown in fig. 1, the present embodiment provides a capacitor complex impedance measurement method with adaptive parasitic capacitance compensation, which is suitable for a measurement circuit including a capacitor to be detected, and the method 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 with adaptive parasitic capacitance compensation for implementing the measurement method as above, the measurement circuit including 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-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.
With specific reference to FIG. 2, as a further implementation, the self-compensating calibration bridge circuit includes a first stage inverse proportional circuit, an integrating circuit, a second stage inverse proportional circuit, and a bandPIA regulated feedback circuit; wherein,
amplifierAnd resistance->The first-stage reverse proportional circuit and the reference capacitor are formed>Series connection with the capacitor to be detected and the automatic compensation capacitor +.>Parallel connection and pass through an operational amplifier>And feedback resistance->Composing the output signal of the integrating circuit>The integrating circuit is then passed through an amplifier>And resistance->The second-stage reverse proportional circuit is composed of the output signals +.>Automatic compensation capacitor->For programmable capacitance, referring to fig. 3 in a specific schematic diagram, the capacitor to be tested comprises leakage capacitance +.>And leakage resistance->。
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 zero when the capacitor to be detected is not connected or the system is powered on in the initial state, 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 isThe integrating circuit output of the self-compensating calibration bridge circuitAnd the integrating circuit outputs the signal +_ via the second-stage inverse proportional circuit>The 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, the phase-controlled rectifying circuitThe circuit comprises a comparator, a reverse proportion circuit and an analog switchS1A second-order low-pass filter circuit; operational amplifierThe reverse input end of the power amplifier is connected with the phase shifting circuit, and the forward input end is connected with the ground.
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 sensor>At this time, no phase shift is required, and the AC signal and the operational amplifier of the next stage are +.>Is 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 groundFor controlling the phase of signals, analog switchesS1Is connected to the output of the self-compensating calibration bridge circuit>A normally closed contact connected to the output terminalWhen the input end shifts 90 degrees for the original excitation signal, the analog switch outputs 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>The method comprises the steps of carrying out a first treatment on the surface of the When the input terminal is the original excitation signal, the real part of the capacitor to be detected is detected>；
Wherein, when detectingWhen the phase of the output signal of the phase shifting circuit is 90 degrees behind the excitation signal, and then the analog switch is controlled by the comparator>The 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 signalThe output direct current after signal integration in one period can be approximately calculated as:
；
detecting imaginary partThe method comprises the following steps:
；
when detectingWhen the analog switch is in use, a phase shift circuit is not needed, and the excitation signal directly passes through the analog switch controlled by the comparator>The 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 signalThe output direct current after signal integration in one period can be approximately calculated as:
；
detecting real partThe 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 limited in this embodiment.
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 each embodiment 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, including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in the embodiments of the present invention. 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 thereof; although the present application has been described in detail with reference to the foregoing embodiments, one of ordinary skill in the art will appreciate 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 (9)
1. A method of measuring complex impedance of a capacitor with adaptive parasitic capacitance compensation, 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.
2. A method of capacitor complex impedance measurement with adaptive parasitic capacitance compensation according to claim 1, wherein the initial state comprises an initial time when the measurement circuit is not connected to the capacitor to be detected or when the measurement circuit is connected to the capacitor to be detected.
3. The method of claim 1, wherein the input sinusoidal ac signal is phase shifted by 90 ° for detecting the real part and by 0 ° for detecting the imaginary part based on the real part and the imaginary part of the capacitor complex to be detected.
4. A capacitor complex impedance measurement circuit with adaptive parasitic capacitance compensation 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 alternating current signal into direct current voltage for output.
5. A capacitor complex impedance measurement circuit with adaptive parasitic capacitance compensation as defined in claim 4, wherein: the self-compensating calibration bridge circuit comprises a first-stage reverse proportional circuit, an integrating circuit, a second-stage reverse proportional circuit and a bandPIA regulated feedback circuit; wherein the amplifierAnd resistance->First-stage reverse proportional circuit and reference capacitor/>Series connection with the capacitor to be detected and the automatic compensation capacitor +.>Parallel connection and pass through an operational amplifier>And feedback resistance->Composing the output signal of the integrating circuit>The integrating circuit is then passed through an amplifier +.>And resistance->The second-stage reverse proportional circuit is composed of the output signals +.>The automatic compensation capacitor>For programmable capacitance, the capacitor to be detected comprises leakage capacitance +.>And leakage resistance->。
6. A capacitor complex impedance measurement circuit with adaptive parasitic capacitance compensation as defined in claim 5, wherein: the phase control rectifying circuitComprises a comparator, a reverse proportion circuit and an analog switchS1A second-order low-pass filter circuit; operational amplifierThe reverse input end of the phase shifting circuit is connected with the phase shifting circuit, and the forward input end is connected with the ground.
7. A capacitor complex impedance measurement circuit with adaptive parasitic capacitance compensation as defined in claim 6, wherein: 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 sensor>At this time, no phase shift is required, and the AC signal and the operational amplifier of the next stage are +.>Is connected to the inverting input terminal of (c).
8. A capacitor complex impedance measurement circuit with adaptive parasitic capacitance compensation as defined in claim 7, wherein: analog switchS1Is connected to the output end of the self-compensating calibration bridge circuitThe normally closed contact is connected to the output terminal>When the input end shifts 90 degrees for the original excitation signal, the analog switch outputs 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>The method comprises the steps of carrying out a first treatment on the surface of the When the input terminal is the original excitation signal, the real part of the capacitor to be detected is detected>；
Wherein, when detectingWhen the phase of the output signal of the phase shifting circuit is 90 degrees behind the excitation signal, and then the analog switch is controlled by the comparator>The 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 signalThe output direct current after signal integration in one period can be approximately calculated as:
；
detecting imaginary partThe method comprises the following steps:
；
when detectingWhen the analog switch is in use, a phase shift circuit is not needed, and the excitation signal directly passes through the analog switch controlled by the comparator>The 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 signalThe output direct current after signal integration in one period can be approximately calculated as:
；
detecting real partThe method comprises the following steps:
。
9. a measuring device comprising a measuring circuit according to any one of claims 4-8.
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| CN202410143577.1A CN117665397B (en) | 2024-02-01 | Capacitor complex impedance measurement method, circuit and device |
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| CN202410143577.1A CN117665397B (en) | 2024-02-01 | Capacitor complex impedance measurement method, circuit and device |
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