Weak current testing device

Abstract

The invention belongs to the technical field of microelectronic metering testing, and particularly discloses a weak current testing device which comprises a lock-in amplifying circuit and a proportion measuring circuit. The output end of the lock-in amplifying circuit is connected with the first input end of the proportion measuring circuit; the first input end of the phase-locked amplification circuit is used for inputting a current signal to be detected; a second input end of the phase-locked amplification circuit is connected with a second input end of the proportion measurement circuit and is used for inputting a reference voltage signal corresponding to a current signal to be measured; the phase-locked amplification circuit is used for performing phase-locked amplification and filtering processing on the current signal to be detected by using the reference voltage signal, and outputting a first analog voltage signal corresponding to the current signal to be detected; the proportion measurement circuit is used for carrying out proportion operation on the first analog voltage signal based on the reference voltage signal and outputting a detection voltage digital signal corresponding to the current signal to be detected. According to the invention, measurement errors caused by frequency and amplitude fluctuation of the to-be-measured signal and the reference signal are reduced, and the precision of weak current detection is improved.

Description

Technical Field

[0001] The present application belongs to the field of microelectronic measurement and testing technology, and more specifically, relates to a weak current testing device. Background Art

[0002] A weak signal refers to a useful signal hidden under a complex strong signal. The amplitude of this weak signal is very small, much smaller than the noise in the circuit, and its amplitude is usually at the microampere, nanoampere, and picoampere levels. With the continuous development of semiconductor manufacturing processes and technical levels, weak current detection technology has been widely used in integrated circuits, biomedicine, aerospace and other fields. At the same time, as the size and accuracy of devices continue to shrink, the requirements for weak current detection accuracy are becoming higher and higher.

[0003] At present, the IV conversion method is usually used for weak current detection, which realizes weak current detection by converting weak current signals into voltage signals. However, in the detection process of this method, due to the influence of the stability of the excitation signal source and the reference signal source themselves, it is easy to be affected by the frequency and amplitude fluctuations of the measurement signal and the reference signal, which introduces measurement errors and reduces the accuracy of weak current detection.

[0004] Therefore, how to better realize weak current detection and improve detection accuracy has become a technical problem that needs to be solved urgently in the industry. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of this application is to better realize weak current detection and improve the detection accuracy. It aims to solve the problem that the existing IV conversion method is easily affected by the frequency and amplitude fluctuations of the measurement signal and the reference signal during its detection process, thereby introducing measurement errors and reducing the accuracy of weak current detection.

[0006] To achieve the above objectives, in a first aspect, the present application provides a weak current testing device, comprising:

[0007] A phase-locked amplifier circuit and a proportional measurement circuit; the output end of the phase-locked amplifier circuit is connected to the first input end of the proportional measurement circuit;

[0008] The first input terminal of the phase-locked amplifier circuit is used to input the current signal to be measured; the second input terminal of the phase-locked amplifier circuit is commonly connected with the second input terminal of the proportional measurement circuit, and is used to input the reference voltage signal corresponding to the current signal to be measured;

[0009] The phase-locked amplifier circuit is used to perform phase-locked amplification and filtering processing on the current signal to be measured using the reference voltage signal, and output a first analog voltage signal corresponding to the current signal to be measured;

[0010] The proportional measurement circuit is used to perform a proportional operation on the first analog voltage signal based on the reference voltage signal, and output a detection voltage digital signal corresponding to the current signal to be measured.

[0011] Optionally, the phase-locked amplifier circuit includes a sensor, a phase-sensitive detection module, and a first conversion circuit, a signal processing module and a phase processing module whose output end is connected to the input end of the phase-sensitive detection module;

[0012] The output end of the sensor is connected to the input end of the signal processing module and the input end of the first conversion circuit respectively;

[0013] The input end of the sensor serves as the first input end of the phase-locked amplifier circuit; the input end of the phase processing module serves as the second input end of the phase-locked amplifier circuit;

[0014] The sensor is used to convert the input current signal to be measured into a second analog voltage signal; the first conversion circuit is used to convert the input second analog voltage signal into a corresponding DC voltage signal;

[0015] The signal processing module is used to perform signal amplification processing on the second analog voltage signal and output a third analog voltage signal;

[0016] The phase processing module is used to perform phase modulation on the input reference voltage signal and output a corresponding fourth analog voltage signal;

[0017] The phase-sensitive detection module is used to perform phase identification and frequency selection on the DC voltage signal, the third analog voltage signal and the fourth analog voltage signal, and output the first analog voltage signal.

[0018] Optionally, the ratio measurement circuit includes an analog-to-digital converter, and a second conversion circuit having an output terminal connected to a second input terminal of the analog-to-digital converter;

[0019] The first input terminal of the analog-to-digital converter serves as the first input terminal of the proportional measurement circuit, and the input terminal of the second conversion circuit serves as the second input terminal of the proportional measurement circuit;

[0020] The output end of the phase-sensitive detection module is connected to the first input end of the analog-to-digital converter;

[0021] The second conversion circuit is used to convert the input reference voltage signal into a DC reference voltage signal;

[0022] The analog-to-digital converter is used to perform analog-to-digital conversion processing on the input first analog voltage signal based on a DC reference voltage signal, and output a detection voltage digital signal corresponding to the current signal to be measured.

[0023] Optionally, the phase-sensitive detection module includes a multiplier and a low-pass filter connected in sequence;

[0024] The multiplier is used to perform multiplication operation on the DC voltage signal, the third analog voltage signal and the fourth analog voltage signal, and output a fifth analog voltage signal;

[0025] The low-pass filter is used to filter out high-frequency components in the fifth analog voltage signal and output the first analog voltage signal.

[0026] Optionally, the signal processing module includes an amplifier and a bandpass filter connected in sequence;

[0027] The amplifier is used to amplify the second analog voltage signal;

[0028] The bandpass filter is used to perform bandpass filtering on the amplified second analog voltage signal and output the third analog voltage signal.

[0029] Optionally, the phase processing module includes a phase-locked loop and a phase shifter connected in sequence.

[0030] Optionally, it also includes:

[0031] Micro control unit;

[0032] The micro control unit is connected to the output end of the proportional measurement circuit, and is used for performing signal analysis on the detection voltage digital signal, and outputting the amplitude and waveform of the detection voltage digital signal.

[0033] Optionally, the micro control unit includes a microcontroller and a digital-to-analog converter connected in sequence, and is used to generate and output the reference voltage signal.

[0034] Optionally, the output terminal of the microcontroller is connected to the input terminal of the digital-to-analog converter;

[0035] The microcontroller is used to generate a digital reference signal corresponding to the current signal to be measured by a signal modulation method; the digital-to-analog converter is used to perform digital-to-analog conversion processing on the digital reference signal and output the reference voltage signal.

[0036] Optionally, the microcontroller unit also includes a first optocoupler isolation module and a second optocoupler isolation module; the output end of the proportional measurement circuit is connected to the input end of the microcontroller through the first optocoupler isolation module; the output end of the microcontroller is connected to the input end of the digital-to-analog converter through the second optocoupler isolation module.

[0037] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art:

[0038] The present application provides a weak current testing device, including a phase-locked amplifier circuit and a proportional measurement circuit. By integrating the proportional measurement method with the phase-locked amplifier technology, the phase-locked amplifier circuit is used to modulate the reference voltage signal, and the current signal to be measured is phase-locked amplified and filtered, so that the current signal to be measured and the reference voltage signal maintain frequency and phase synchronization, and signal superposition and filtering are performed, so as to remove the influence of the fluctuation of the frequency and amplitude of the current signal to be measured and the frequency of the reference voltage signal, and output an analog voltage signal corresponding to the current signal to be measured; and then, through the proportional measurement circuit, the reference voltage signal is used to perform proportional operation on the above analog voltage signal, and the influence of the amplitude fluctuation of the reference signal is further eliminated, and finally the detection voltage digital signal corresponding to the current signal to be measured is output, which can reduce the measurement error introduced by the frequency and amplitude fluctuation of the signal to be measured and the reference signal, improve the accuracy of weak current detection, and reduce the requirements of the device on the stability of the excitation signal source and the reference signal source. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is one of the structural schematic diagrams of the weak current testing device provided in the embodiment of the present application;

[0040] Figure 2 This is the second structural schematic diagram of the weak current testing device provided in the embodiment of the present application;

[0041] Figure 3 It is a schematic diagram of the signal processing principle of the weak current testing device provided in an embodiment of the present application;

[0042] Figure 4 This is the third structural schematic diagram of the weak current testing device provided in the embodiment of the present application. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0044] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects. For example, a first conversion circuit and a second conversion circuit are used to distinguish conversion circuits with different functions rather than to describe a specific order of the conversion circuits.

[0045] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0046] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0047] Figure 1 is one of the structural schematic diagrams of the weak current testing device provided in the embodiment of the present application, such as Figure 1 As shown, the device comprises:

[0048] A phase-locked amplifier circuit 1 and a proportional measurement circuit 2; the output end of the phase-locked amplifier circuit 1 is connected to the first input end of the proportional measurement circuit 2;

[0049] The first input terminal of the phase-locked amplifier circuit 1 is used to input the current signal to be measured; the second input terminal of the phase-locked amplifier circuit is commonly connected with the second input terminal of the proportional measurement circuit 2, and is used to input the reference voltage signal corresponding to the current signal to be measured;

[0050] The phase-locked amplifier circuit 1 is used to perform phase-locked amplification and filtering processing on the current signal to be measured using the reference voltage signal, and output a first analog voltage signal corresponding to the current signal to be measured;

[0051] The proportional measurement circuit 2 is used to perform proportional operation on the first analog voltage signal based on the reference voltage signal, and output a detection voltage digital signal corresponding to the current signal to be measured.

[0052] Specifically, the current signal to be measured described in the embodiment of the present application refers to a weak current signal to be measured. It is generally expressed as an alternating current signal, which is an analog signal and can be expressed as:

[0053]

[0054] In the formula, A represents the amplitude of the current signal to be measured, ω represents the frequency of the current signal to be measured, represents the phase of the current signal to be measured, and N(t) represents the total noise carried by the signal.

[0055] The reference voltage signal described in the embodiment of the present application is used to evaluate, correct or adjust the current signal to be measured, which can be set to an AC voltage signal with the same frequency as the current signal to be measured, and the expression can be expressed as:

[0056]

[0057] Wherein, B represents the amplitude of the reference voltage signal; ω represents the frequency of the reference voltage signal, which is the same frequency as the current signal to be measured; Indicates the phase of the reference voltage signal.

[0058] The first analog voltage signal described in the embodiment of the present application refers to the analog voltage signal output by the phase-locked amplifier circuit 1 after the current signal to be measured and the reference voltage signal are simultaneously input into the phase-locked amplifier circuit 1 for processing.

[0059] The detection voltage digital signal described in the embodiment of the present application refers to a voltage digital signal used to measure weak current based on the principle of current conversion into voltage measurement.

[0060] In an embodiment of the present application, a weak current test device is constructed based on a phase-locked amplifier circuit 1 and a proportional measurement circuit 2. The phase-locked amplifier circuit 1 has two input terminals, a first input terminal for inputting a current signal to be measured, and a second input terminal for inputting a reference voltage signal. The second input terminal of the phase-locked amplifier circuit 1 is connected in common with the second input terminal of the proportional measurement circuit 2, so that the reference voltage signal is divided into two paths, one path is input into the phase-locked amplifier circuit 1, and the other path is input into the proportional measurement circuit 2.

[0061] When the reference voltage signal and the current signal to be measured are simultaneously input into the phase-locked amplifier circuit 1, the phase-locked amplifier circuit 1 can process the current signal to be measured and the reference voltage signal through internal functional subcircuits such as phase locking, amplification, and filtering. Specifically, the reference voltage signal can be used to perform phase-locked amplification and filtering on the current signal to be measured, so that the current signal to be measured and the reference voltage signal maintain frequency and phase synchronization, and the two types of signals are superimposed and filtered, so as to achieve the purpose of removing the influence of the frequency and amplitude of the current signal to be measured and the frequency fluctuation of the reference voltage signal, and finally output the first analog voltage signal corresponding to the current signal to be measured.

[0062] Furthermore, in an embodiment of the present application, the proportional measurement circuit 2 can be constructed based on an AC / DC conversion circuit and an analog-to-digital converter to implement proportional operation of the signal. The phase-locked amplifier circuit 1 outputs the first analog voltage signal to the proportional measurement circuit 2, and the proportional measurement circuit 2 can generate a corresponding reference voltage signal based on the reference voltage signal, and then perform proportional operation with the first analog voltage signal to further eliminate the influence of the amplitude fluctuation of the reference voltage signal, and finally output a detection voltage digital signal corresponding to the current signal to be measured.

[0063] The weak current testing device of the embodiment of the present application includes a phase-locked amplifier circuit and a proportional measurement circuit. By integrating the proportional measurement method with the phase-locked amplifier technology, the phase-locked amplifier circuit is used to modulate the reference voltage signal, and the current signal to be measured is phase-locked amplified and filtered, so that the current signal to be measured and the reference voltage signal maintain frequency and phase synchronization, and signal superposition and filtering are performed, thereby removing the influence of fluctuations in the frequency and amplitude of the current signal to be measured and the frequency of the reference voltage signal, and outputting an analog voltage signal corresponding to the current signal to be measured; and then through the proportional measurement circuit, the reference voltage signal is used to perform proportional operations on the above analog voltage signal, further eliminating the influence of the amplitude fluctuation of the reference signal, and finally outputting a detection voltage digital signal corresponding to the current signal to be measured, which can reduce the measurement error introduced by the frequency and amplitude fluctuations of the signal to be measured and the reference signal, improve the accuracy of weak current detection, and reduce the requirements of the device on the stability of the excitation signal source and the reference signal source.

[0064] Figure 2 This is the second structural diagram of the weak current testing device provided in the embodiment of the present application. Figure 2 As shown, as an optional embodiment, the phase-locked amplifier circuit 1 may include a sensor 11, a phase-sensitive detection module 12, a first conversion circuit 13 whose output end is connected to the input end of the phase-sensitive detection module 12, a signal processing module 14 and a phase processing module 15;

[0065] The output end of the sensor 11 is connected to the input end of the signal processing module 14 and the input end of the first conversion circuit 13 respectively;

[0066] The input end of the sensor 11 is connected together as the first input end of the phase-locked amplifier circuit 1; the input end of the phase processing module 15 is connected together as the second input end of the phase-locked amplifier circuit 1;

[0067] The sensor 11 is used to convert the input current signal to be measured into a second analog voltage signal; the first conversion circuit is used to convert the input second analog voltage signal into a corresponding DC voltage signal;

[0068] The signal processing module 14 is used to perform signal amplification processing on the second analog voltage signal and output a third analog voltage signal;

[0069] The phase processing module 15 is used to perform phase modulation on the input reference voltage signal and output a corresponding fourth analog voltage signal;

[0070] The phase-sensitive detection module 12 is used to perform phase identification and frequency selection on the DC voltage signal, the third analog voltage signal and the fourth analog voltage signal, and output a first analog voltage signal.

[0071] Specifically, the first conversion circuit described in the embodiment of the present application refers to an alternating current / direct current (AC / DC) conversion circuit for converting an input current signal to be measured into a direct current voltage signal.

[0072] The second analog voltage signal described in the embodiment of the present application refers to an analog voltage signal obtained by converting the current signal to be measured by the sensor 11. The sensor 11 can be an electromagnetic sensor, which is made of enameled wire wound on a non-magnetic frame to realize the conversion of current signal to voltage signal, and a cylindrical electromagnetic induction coil can be selected.

[0073] The third analog voltage signal described in the embodiment of the present application refers to an analog voltage signal obtained by amplifying the second analog voltage signal through the signal processing module 14. It can be understood that the third analog voltage signal contains information of the current signal to be measured.

[0074] The fourth analog voltage signal described in the embodiment of the present application refers to an analog voltage signal obtained by phase-modulating an input reference voltage signal through the phase processing module 15 .

[0075] In an embodiment of the present application, the input end of the first conversion circuit 13 is connected to the input end of the sensor 11 as the first input end of the phase-locked amplifier circuit 1, and is used to simultaneously input the current signal to be measured. The current signal to be measured can be converted into a DC voltage signal through the AC-DC conversion process of the first conversion circuit 13. At the same time, the current signal to be measured can be converted into a second analog voltage signal through the sensor 11, such as an electromagnetic sensor. Further, the second analog voltage signal is transmitted to the signal processing module 14, and the second analog voltage signal is amplified by the signal processing module 14 to output a third analog voltage signal.

[0076] In the embodiment of the present application, the input end of the phase processing module 15 is used as the second input end of the phase-locked amplifier circuit 1 to input a reference voltage signal. The phase processing module 15 performs phase modulation on the input reference voltage signal and outputs a fourth analog voltage signal corresponding to the reference voltage signal.

[0077] Furthermore, in an embodiment of the present application, the phase-sensitive detection module includes three data channels, the first channel is connected to the first conversion circuit 13 to provide a DC voltage; the second channel is connected to the signal processing module 14 to obtain the signal information to be measured; and the third channel is connected to the phase processing module 15 to obtain reference signal information.

[0078] In this way, the three signals of the above-mentioned DC voltage signal, the third analog voltage signal containing the information of the current signal to be measured, and the fourth analog voltage signal containing the information of the reference voltage signal will be input into the phase-sensitive detection module 12. Through the calculation and filtering functions of the phase-sensitive detection module 12, the above-mentioned DC voltage signal, the third analog voltage signal and the fourth analog voltage signal can be phase-identified and frequency-selective filtered, and finally the analog voltage signal corresponding to the current signal to be measured, that is, the first analog voltage signal, is output.

[0079] Optionally, in the embodiment of the present application, the AC / DC conversion circuit may use a power chip of model HFC0500 to convert an AC signal into a DC signal.

[0080] The device of the embodiment of the present application, by constructing a phase-locked amplifier circuit using a sensor, an AC / DC conversion circuit, a signal processing module, a phase processing module and a phase-sensitive detection module, can effectively realize phase-locked amplification and filtering of the current signal to be measured, so as to remove the influence of fluctuations in the frequency and amplitude of the current signal to be measured and the frequency of the reference voltage signal, thereby ensuring the reliability of circuit signal processing.

[0081] Based on the content of the above embodiment, as an optional embodiment, the ratio measurement circuit 2 includes an analog-to-digital converter 21, and a second conversion circuit 22 whose output terminal is connected to the second input terminal of the analog-to-digital converter (ADC) 21;

[0082] The first input terminal of the analog-to-digital converter 21 serves as the first input terminal of the ratio measurement circuit 2, and the input terminal of the second conversion circuit 22 serves as the second input terminal of the ratio measurement circuit 2;

[0083] The output end of the phase-sensitive detection module 12 is connected to the first input end of the analog-to-digital converter 21;

[0084] The second conversion circuit 22 is used to convert the input reference voltage signal into a DC reference voltage signal;

[0085] The analog-to-digital converter 21 is used to perform analog-to-digital conversion processing on the input first analog voltage signal based on the DC reference voltage signal, and output a detection voltage digital signal corresponding to the current signal to be measured.

[0086] Specifically, the second conversion circuit described in the embodiment of the present application refers to an AC / DC conversion circuit for converting an input reference voltage signal into a direct current voltage signal.

[0087] The DC reference voltage signal described in the embodiment of the present application refers to a DC voltage signal obtained by performing AC / DC conversion on a reference voltage signal using an AC / DC conversion circuit.

[0088] In an embodiment of the present application, the ratio measurement circuit 2 includes an analog-to-digital converter 21 and a second conversion circuit 22. The input end of the second conversion circuit 22 serves as the second input end of the ratio measurement circuit 2, and is used to input a reference voltage signal, and convert the reference voltage signal into a corresponding DC reference voltage signal, so as to serve as a reference voltage of the analog-to-digital converter 21.

[0089] Furthermore, the first analog voltage signal output by the phase-sensitive detection module 12 is received by the analog-to-digital converter 21, and the DC reference voltage signal output by the second conversion circuit 22 can be used as a reference voltage to perform analog-to-digital conversion on the input first analog voltage signal, so that the first analog voltage signal is used as the numerator voltage and the DC reference voltage signal is used as the denominator voltage to perform proportional measurement operations, and finally a detection voltage digital signal corresponding to the current signal to be measured is output.

[0090] Optionally, the analog-to-digital converter 21 may use an ADC conversion chip of model LTC2400, and the AC / DC conversion circuit may use an HFC0500 power supply chip.

[0091] The device of the embodiment of the present application constructs a proportional measurement circuit by utilizing an analog-to-digital converter and an AC / DC conversion circuit, so that the AC / DC conversion circuit converts a reference signal into a DC reference voltage as a reference voltage for the analog-to-digital converter, thereby achieving proportional measurement of the signal to be measured and the reference signal, further eliminating the influence of the amplitude fluctuation of the reference signal, and reducing the measurement error introduced by the amplitude fluctuation of the reference signal.

[0092] Continue to refer to Figure 2 Based on the content of the above embodiment, as an optional embodiment, the phase-sensitive detection module 12 includes a multiplier 121 and a low-pass filter 122 connected in sequence;

[0093] The multiplier 121 is used to perform multiplication operation on the DC voltage signal, the third analog voltage signal and the fourth analog voltage signal, and output a fifth analog voltage signal;

[0094] The low-pass filter 122 is used to filter out high-frequency components in the fifth analog voltage signal and output the first analog voltage signal.

[0095] Specifically, the fifth analog voltage signal described in the embodiment of the present application refers to an analog voltage signal obtained by the multiplier performing a multiplication proportional operation on the received DC voltage signal, the third analog voltage signal and the fourth analog voltage signal.

[0096] In the embodiment of the present application, the phase-sensitive detection module 12 can be constructed using the multiplier 121 and the low-pass filter 122. The multiplier 121 divides three data channels, which are respectively used to receive the DC voltage signal, the third analog voltage signal and the fourth analog voltage signal, and then the multiplier 121 can perform multiplication proportional operations on the three signals, and the third analog voltage signal and the fourth analog voltage signal provide the numerator voltage of the multiplier 121, and the DC voltage signal provides the denominator voltage of the analog multiplier 121, and finally outputs the fifth analog voltage signal.

[0097] Furthermore, in an embodiment of the present application, the high-frequency signal components in the fifth analog voltage signal are filtered out by a low-pass filter 122 to filter out various noise signals other than the frequency of the current signal to be measured, and finally a stable DC signal is obtained, that is, the first analog voltage signal is output.

[0098] Optionally, the multiplier 121 may use a high-precision, high-speed, low-noise analog multiplier AD734, and the low-pass filter 122 may use a low-pass filter circuit designed with a precision operational amplifier OP07.

[0099] The device of the embodiment of the present application builds a phase-sensitive detection module through a multiplier and a low-pass filter, and utilizes the multiplication ratio and filtering effect to effectively perform phase identification and frequency selection filtering processing on the above-mentioned DC voltage signal, the third analog voltage signal and the fourth analog voltage signal, thereby providing reliable signal information for subsequent analog-to-digital conversion processing.

[0100] Figure 3 Schematic diagram of the signal processing principle of the weak current testing device provided in the embodiment of the present application. Figure 3 As shown, in the embodiment of the present application, when the current signal A to be measured is converted into a DC voltage signal after passing through the sensor 11 and the first conversion circuit 13. For example, assuming that K1 represents the sensitivity coefficient of the sensor 11, and P1 is the conversion coefficient of the first conversion circuit 13, when the conversion circuit structure is constant, both can be regarded as constants. Then the DC voltage signal V1 can be expressed as:

[0101] V1=K1×P1×A;

[0102] Next, the current signal A to be measured is processed by the sensor 11 and the signal processing module 14, and a third analog voltage signal V2 is output, which can be expressed as:

[0103]

[0104] In the formula, K1 represents the sensitivity coefficient of the sensor 11, and K2 represents the gain of the signal processing circuit 14, and both are constants when the circuit structure is constant.

[0105] The signals V1, V2, and V3 are passed through the multiplier 121 in the phase-sensitive detection module 12 to obtain:

[0106]

[0107] Wherein: V1 provides the denominator voltage of the analog multiplier 121, and V2 and V3 provide the numerator voltage of the analog multiplier 121. Wherein, V3 represents the fourth analog voltage signal.

[0108] After the high-frequency signal is filtered out by the low-pass filter 122 in the phase-sensitive detection module 12, a stable DC voltage signal V5 is finally obtained, which can be expressed as:

[0109]

[0110] Wherein, K3 represents the passband gain of the low-pass filter 122, which is a constant when the circuit structure is constant.

[0111] Furthermore, the reference voltage signal is converted into a DC reference voltage signal through the second conversion circuit 22, which is used to provide a reference voltage for the analog-to-digital converter 21. Assuming that P2 represents the conversion coefficient of the second conversion circuit 22, when the conversion circuit structure is constant, it can be regarded as a constant, then the DC reference voltage signal V ref It can be expressed as:

[0112] V ref =P2×B;

[0113] Finally, the digital output voltage of the analog-to-digital converter 21, that is, the detection voltage digital signal W, can be expressed as:

[0114]

[0115] Wherein: N represents the number of bits of the analog-to-digital converter 21.

[0116] It can be seen from the expression of the detection voltage digital signal W that it is independent of the amplitude and frequency of the current signal to be measured and the reference voltage signal, so the requirements on the stability of the excitation signal source and the reference signal source can be effectively reduced.

[0117] Continue to refer to Figure 2 , based on the content of the above embodiment, as an optional embodiment, the signal processing module 14 includes an amplifier 141 and a bandpass filter 142 connected in sequence;

[0118] The amplifier 141 is used to amplify the second analog voltage signal;

[0119] The bandpass filter 142 is used to perform bandpass filtering on the amplified second analog voltage signal and output a third analog voltage signal.

[0120] Specifically, in the embodiment of the present application, the signal processing module 14 includes an amplifier 141 and a bandpass filter 142 connected in sequence, and the precision operational amplifier OP07 can be used to design the relevant circuit. The received second analog voltage signal is amplified by the amplifier, and then the amplified analog voltage signal is bandpass filtered by the bandpass filter to obtain a fixed frequency signal consistent with the frequency of the current signal to be measured, that is, the third analog voltage signal is output.

[0121] The device of the embodiment of the present application can effectively amplify and bandpass filter the voltage signal corresponding to the current signal to be measured by constructing a signal processing module using an amplifier and a bandpass filter, thereby ensuring the reliability of signal processing.

[0122] Based on the content of the above embodiment, as an optional embodiment, the phase processing module 15 includes a phase-locked loop 151 and a phase shifter 152 connected in sequence.

[0123] Specifically, in the embodiment of the present application, a phase processing module 15 is constructed by using a phase-locked loop 151 and a phase shifter 152 connected in sequence. Specifically, a direct digital synthesizer (DDS) chip of model AD9834 can be selected to realize signal frequency synthesis to phase modulate the input reference voltage signal to ensure the accuracy of the output modulated analog voltage signal.

[0124] Figure 4 This is the third structural diagram of the weak current testing device provided in the embodiment of the present application, such as Figure 4 As shown, the device also includes:

[0125] Micro control unit 3;

[0126] The micro control unit 3 is connected to the output end of the proportional measurement circuit 2 and is used for performing signal analysis on the detection voltage digital signal and outputting the amplitude and waveform of the detection voltage digital signal.

[0127] Specifically, in the embodiment of the present application, a micro control unit 3 may be introduced, which is connected to the output end of the proportional measurement circuit 2 and is used to perform signal analysis on the detection voltage digital signal, detect and output the amplitude and waveform of the detection voltage digital signal.

[0128] Optionally, the micro control unit 3 may also be added with a display module for displaying the amplitude and waveform of the detection voltage digital signal for viewing by the front end.

[0129] The device of the embodiment of the present application, by introducing a microcontroller unit, can analyze the detection voltage digital signal output by the analog-to-digital converter in real time, and output the amplitude and waveform of the detection voltage digital signal, which is beneficial to improving the visualization level of weak current detection and facilitating more intuitive acquisition of weak current detection results.

[0130] Based on the content of the above embodiment, as an optional embodiment, the micro control unit 3 includes a microcontroller 31 and a digital-to-analog converter (ADC) 32 connected in sequence, which are used to generate and output a reference voltage signal.

[0131] Specifically, in the embodiment of the present application, a microcontroller 31 and a digital-to-analog converter 32 are used to construct a microcontroller unit 3. Optionally, the microcontroller 31 can use a microcontroller chip of model STM32F103ZET6, and the digital-to-analog converter 32 can use an ADC conversion chip of model AD1933. Through the constructed microcontroller unit 3, a corresponding reference voltage signal can be generated and output according to the frequency characteristics of the current signal to be measured. At the same time, the output end of the proportional measurement circuit 2 is connected to the input end of the microcontroller 31. After receiving the detection voltage digital signal output by the proportional measurement circuit 2, the microcontroller 31 can analyze the detection voltage digital signal output by the analog-to-digital converter 21 in real time through a preset detection program, and output the amplitude and waveform of the detection voltage digital signal.

[0132] The device of the embodiment of the present application can also realize the function of generating a reference voltage signal and provide a reference signal source by constructing a microcontroller using a microcontroller and a digital-to-analog converter.

[0133] Based on the content of the above embodiment, as an optional embodiment, the output end of the microcontroller 31 is connected to the input end of the digital-to-analog converter 32;

[0134] The microcontroller 31 is used to generate a digital reference signal corresponding to the current signal to be measured by a signal modulation method; the digital-to-analog converter 32 is used to perform digital-to-analog conversion on the digital reference signal and output a reference voltage signal.

[0135] Specifically, in the embodiment of the present application, the output end of the microcontroller 31 is connected to the input end of the digital-to-analog converter 32. Through the signal modulation method, the microcontroller 31 can generate a reference voltage signal corresponding to the frequency characteristic parameter of the current signal to be measured. The frequency characteristic parameter of the current signal to be measured can be set based on actual experience.

[0136] The device of the embodiment of the present application performs signal modulation through a microcontroller and combines the digital-to-analog conversion function of a digital-to-analog converter to effectively output a reference voltage signal corresponding to the current signal to be measured, so as to be used for evaluating, correcting or adjusting the current signal to be measured, thereby further improving the reliability of the reference voltage signal source.

[0137] Based on the contents of the above embodiments, as an optional embodiment, the microcontroller unit 3 also includes a first optocoupler isolation module 33 and a second optocoupler isolation module 34; the output end of the proportional measurement circuit 2 is connected to the input end of the microcontroller 31 through the first optocoupler isolation module 33; the output end of the microcontroller 31 is connected to the input end of the digital-to-analog converter 32 through the second optocoupler isolation module 34.

[0138] Specifically, in the embodiment of the present application, two optocoupler isolation modules are introduced into the microcontroller unit, namely, a first optocoupler isolation module 33 and a second optocoupler isolation module 34. The first optocoupler isolation module 33 is connected between the output end of the proportional measurement circuit 2 and the input end of the microcontroller 31; the second optocoupler isolation module 34 is connected between the output end of the microcontroller 31 and the input end of the digital-to-analog converter 32.

[0139] Optionally, both of the above two optocoupler isolation modules can use an optocoupler isolation chip of model TLP521.

[0140] The device of the embodiment of the present application introduces an optical coupling isolation module to isolate analog signals that may be mixed in the digital signal processing process, thereby enhancing the signal anti-interference capability of the device.

[0141] It should be understood that expressions such as "including" and "may include" that may be used in the present application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0142] It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0143] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A weak current testing device, characterized in that: include: A phase-locked amplifier circuit and a proportional measurement circuit; the output end of the phase-locked amplifier circuit is connected to the first input end of the proportional measurement circuit; The first input terminal of the phase-locked amplifier circuit is used to input the current signal to be measured; the second input terminal of the phase-locked amplifier circuit is commonly connected with the second input terminal of the proportional measurement circuit, and is used to input the reference voltage signal corresponding to the current signal to be measured; The phase-locked amplifier circuit is used to perform phase-locked amplification and filtering processing on the current signal to be measured using the reference voltage signal, and output a first analog voltage signal corresponding to the current signal to be measured; The proportional measurement circuit is used to perform a proportional operation on the first analog voltage signal based on the reference voltage signal, and output a detection voltage digital signal corresponding to the current signal to be measured.

2. The weak current testing device according to claim 1, characterized in that: The phase-locked amplifier circuit includes a sensor, a phase-sensitive detection module, and a first conversion circuit, a signal processing module and a phase processing module whose output end is connected to the input end of the phase-sensitive detection module; The output end of the sensor is connected to the input end of the signal processing module and the input end of the first conversion circuit respectively; The input end of the sensor serves as the first input end of the phase-locked amplifier circuit; the input end of the phase processing module serves as the second input end of the phase-locked amplifier circuit; The sensor is used to convert the input current signal to be measured into a second analog voltage signal; the first conversion circuit is used to convert the input second analog voltage signal into a corresponding DC voltage signal; The signal processing module is used to perform signal amplification processing on the second analog voltage signal and output a third analog voltage signal; The phase processing module is used to perform phase modulation on the input reference voltage signal and output a corresponding fourth analog voltage signal; The phase-sensitive detection module is used to perform phase identification and frequency selection on the DC voltage signal, the third analog voltage signal and the fourth analog voltage signal, and output the first analog voltage signal.

3. The weak current testing device according to claim 2, characterized in that: The ratio measurement circuit includes an analog-to-digital converter, and a second conversion circuit having an output terminal connected to a second input terminal of the analog-to-digital converter; The first input terminal of the analog-to-digital converter serves as the first input terminal of the proportional measurement circuit, and the input terminal of the second conversion circuit serves as the second input terminal of the proportional measurement circuit; The output end of the phase-sensitive detection module is connected to the first input end of the analog-to-digital converter; The second conversion circuit is used to convert the input reference voltage signal into a DC reference voltage signal; The analog-to-digital converter is used to perform analog-to-digital conversion processing on the input first analog voltage signal based on a DC reference voltage signal, and output a detection voltage digital signal corresponding to the current signal to be measured.

4. The weak current testing device according to claim 2, characterized in that: The phase-sensitive detection module includes a multiplier and a low-pass filter connected in sequence; The multiplier is used to perform multiplication operation on the DC voltage signal, the third analog voltage signal and the fourth analog voltage signal, and output a fifth analog voltage signal; The low-pass filter is used to filter out high-frequency components in the fifth analog voltage signal and output the first analog voltage signal.

5. The weak current testing device according to claim 2, characterized in that: The signal processing module includes an amplifier and a bandpass filter connected in sequence; The amplifier is used to amplify the second analog voltage signal; The bandpass filter is used to perform bandpass filtering on the amplified second analog voltage signal and output the third analog voltage signal.

6. The weak current testing device according to claim 2, characterized in that: The phase processing module includes a phase-locked loop and a phase shifter which are connected in sequence.

7. The weak current testing device according to any one of claims 1 to 6, characterized in that: Also includes: Micro control unit; The micro control unit is connected to the output end of the proportional measurement circuit, and is used for performing signal analysis on the detection voltage digital signal, and outputting the amplitude and waveform of the detection voltage digital signal.

8. The weak current testing device according to claim 7, characterized in that: The micro control unit includes a micro controller and a digital-to-analog converter connected in sequence, and is used to generate and output the reference voltage signal.

9. The weak current testing device according to claim 8, characterized in that: The output end of the microcontroller is connected to the input end of the digital-to-analog converter; The microcontroller is used to generate a digital reference signal corresponding to the current signal to be measured by a signal modulation method; the digital-to-analog converter is used to perform digital-to-analog conversion processing on the digital reference signal and output the reference voltage signal.

10. The weak current testing device according to claim 9, characterized in that: The microcontroller unit also includes a first optocoupler isolation module and a second optocoupler isolation module; the output end of the proportional measurement circuit is connected to the input end of the microcontroller through the first optocoupler isolation module; the output end of the microcontroller is connected to the input end of the digital-to-analog converter through the second optocoupler isolation module.

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