CN116500331B - Low-frequency alternating-current voltage precise differential measurement system and measurement method - Google Patents
Low-frequency alternating-current voltage precise differential measurement system and measurement method Download PDFInfo
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Abstract
The invention discloses a low-frequency alternating voltage precise differential measurement system and a measurement method. The measurement system includes: the reference voltage signal generation module is used for generating an analog reference voltage signal; the voltage signal generating module to be tested is used for generating an analog voltage signal to be tested; the sampling module is used for sampling the reference voltage signal, measuring the voltage of each step, sampling the voltage difference signal between the analog reference voltage signal and the analog voltage signal to be measured, and measuring the voltage difference of each step. The invention uses the existing commercial instrument as a reference voltage signal generating module, a voltage signal generating module to be tested and a sampling module to form a measuring system which can operate in a normal temperature environment to replace an alternating current signal precision differential sampling measuring system based on a programmable Josephson voltage standard, so that ppm-level measurement can be realized on an alternating current signal sent by a calibration source, experimental conditions and operation are simplified, and meanwhile, experimental cost is reduced.
Description
Technical Field
The invention belongs to the field of metering test instruments, and particularly relates to a low-frequency alternating-current voltage precise differential measurement system and a measurement method.
Background
In recent years, ac signal precision differential sampling measurement based on programmable josephson voltage standard (Programmable Josephson Voltage Standard, PJVS) has been widely used in metering institutions in various countries; since the intermediate flat part of the ladder wave generated by the PJVS can reach the accuracy of the quantum level, the amplitude and phase information of the unknown alternating voltage signal can be accurately measured by a differential sampling technology based on the PJVS; however, because the josephson junction array chip needs to perform experimental operation in the environment of liquid helium, and the josephson devices and systems are quite expensive, the measurement method has high running cost and complex operation, so that the measurement of alternating current signals by using a differential sampling technology based on PJVS can only be performed in a laboratory; in daily measurement, a commercial analog-to-digital converter such as Agilent3458A is often used for directly measuring an alternating current signal, but the measurement accuracy of the direct measurement is relatively low. In view of the foregoing, there is a need for an ac voltage high-precision measurement system with a relatively low operating cost and a relatively simple system structure.
The information disclosed in the background section of the invention is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide a low-frequency alternating-current voltage precise differential measurement system and a measurement method, which can operate a differential sampling system in a normal-temperature environment and can realize ppm-level measurement on an alternating-current signal sent by a calibration source.
In order to achieve the above purpose, the present invention provides a precise differential measurement system and a measurement method for low-frequency ac voltage.
According to a first aspect of the present invention, there is provided a low frequency ac voltage precision differential measurement system comprising:
the reference voltage signal generation module is used for generating an analog reference voltage signal;
the voltage signal generating module to be tested is used for generating an analog voltage signal to be tested;
the sampling module is used for sampling the reference voltage signal and measuring the voltage of each step; and sampling a voltage difference signal between the analog reference voltage signal and the analog voltage signal to be detected, and measuring the voltage difference of each step.
Optionally, the method further comprises:
the optocoupler isolation modules are connected between the voltage signal generating module to be tested, the reference voltage signal generating module and the sampling module.
Optionally, the reference voltage signal generating module includes:
and the digital-to-analog converter is used for converting an external digital reference voltage signal into the analog reference voltage signal.
Optionally, the voltage signal to be measured generating module includes:
the alternating current signal calibration source to be tested is used for generating the analog voltage signal to be tested;
the first signal generator is used for respectively transmitting an external trigger signal and a sampling trigger signal to the reference voltage signal generation module and the sampling module, and simultaneously transmitting a phase locking signal to the alternating current signal calibration source to be tested to adjust the phase of the analog voltage signal to be tested;
the low end of the alternating current signal calibration source to be tested is electrically connected with the low end of the digital-to-analog converter, a first output port of the first signal generator is connected with a trigger port of the digital-to-analog converter through the first optical coupling isolation module, and a second output port of the first signal generator is electrically connected with an external phase locking port of the alternating current signal calibration source to be tested through the second optical coupling isolation module.
Optionally, the sampling module includes:
the analog-to-digital converter is used for measuring the voltage value of each step of the analog reference voltage signal and measuring the voltage difference value of each step between the analog reference voltage signal and the analog voltage signal to be measured;
a second signal generator for transmitting a time-based signal to the analog-to-digital converter;
the trigger port of the analog-to-digital converter is electrically connected with the first output port of the first signal generator through the third optocoupler isolation module, the time base port of the analog-to-digital converter is electrically connected with the output port of the second signal generator, the high end of the analog-to-digital converter is electrically connected with the high end of the digital-to-analog converter, and the low end of the analog-to-digital converter is electrically connected with the high end of the calibration source of the alternating current signal to be tested.
Optionally, the method further comprises:
the time base module is used for synchronizing the time of the digital-to-analog converter, the first signal generator and the second signal generator by sending time base signals, so that the reference voltage signal generation module, the voltage signal generation module to be tested and the sampling module realize time base synchronization;
the time base module is electrically connected with the digital-to-analog converter through a fourth optical coupling isolation module, the time base module is electrically connected with an external reference clock port of the first signal generator through a fifth optical coupling isolation module, and the time base module is electrically connected with an external reference clock port of the second signal generator through a sixth optical coupling isolation module.
Optionally, the analog reference voltage signal is a sine step wave voltage signal with the same frequency and the same phase as the analog voltage signal to be measured and with the amplitude close to the analog voltage signal to be measured.
Optionally, the analog voltage signal to be measured is a spectrally pure sine wave voltage signal.
According to a second aspect of the present invention, there is provided a precision differential measurement method of a low-frequency ac voltage, comprising:
the method comprises the steps that the high end of a reference voltage signal generating module is electrically connected with the high end of a sampling module, the low end of the reference voltage signal generating module is electrically connected with the low end of the sampling module, and then the sampling module is used for sampling an analog reference voltage signal generated by the reference voltage signal generating module, so that the voltage value of each step is measured;
after the measurement is completed, the high end of the reference voltage signal generating module is electrically connected with the high end of the sampling module, the low end of the reference voltage signal generating module is electrically connected with the low end of the voltage signal generating module to be measured, the low end of the sampling module is electrically connected with the high end of the voltage signal generating module to be measured, and then the voltage difference signal between the analog reference voltage signal and the analog voltage signal to be measured is sampled through the sampling module, so that the voltage difference of each step is measured.
Optionally, the method further comprises:
adding the voltage difference value and the voltage value of each step to obtain a reconstructed signal; and performing discrete Fourier transform on the reconstructed signal to obtain the to-be-detected waveform amplitude and phase information of the analog to-be-detected voltage signal.
The invention has the beneficial effects that: the step voltage of the existing commercial digital-to-analog converter is precisely measured, the existing commercial instrument is used for replacing PJVS, a differential sampling system which can operate in a normal temperature environment is built, and ppm-level measurement can be realized on an alternating current signal sent by a calibration source; the experimental conditions and operation are simplified, and meanwhile, the experimental cost is reduced.
The system of the present invention has other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.
Drawings
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular descriptions of exemplary embodiments of the invention as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the invention.
Fig. 1 shows a schematic diagram of a low frequency ac voltage precision differential measurement system according to the present invention.
Fig. 2 shows a schematic diagram of a low frequency ac voltage precision differential measurement system according to embodiment 1 of the present invention.
Fig. 3 shows waveforms of a trigger signal, a phase lock signal, an analog reference voltage signal, and an analog voltage signal to be measured according to embodiment 1 of the present invention.
Fig. 4 shows a step diagram of a precision differential measurement of a low frequency ac voltage according to embodiment 2 of the present invention.
Reference numerals illustrate:
a. an external trigger signal, a sampling trigger signal, b, a phase locking signal, c, an analog reference voltage signal, d, an analog voltage signal to be detected; 1. the device comprises a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), a calibration source of an alternating current signal to be tested, a first signal generator (4), a second signal generator (5), a second signal generator (6), a first optocoupler isolation module (7), a second optocoupler isolation module (8), a third optocoupler isolation module (9), a fourth optocoupler isolation module (10), a fifth optocoupler isolation module (11), a sixth optocoupler isolation module (12) and a time base module.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are illustrated in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
As shown in fig. 1, a low-frequency ac voltage precise differential measurement system according to the present invention includes:
the reference voltage signal generation module is used for generating an analog reference voltage signal;
the voltage signal generating module to be tested is used for generating an analog voltage signal to be tested;
the sampling module is used for sampling the reference voltage signal and measuring the voltage of each step; and sampling a voltage difference signal between the analog reference voltage signal and the analog voltage signal to be detected, and measuring the voltage difference of each step.
In one example, in the present invention, further comprising:
the optocoupler isolation modules are connected between the voltage signal generating module to be tested, the reference voltage signal generating module and the sampling module.
In one example, in the present invention, the reference voltage signal generation module includes:
and the digital-to-analog converter is used for converting an external digital reference voltage signal into an analog reference voltage signal.
In one example, in the present invention, a voltage signal generating module to be measured includes:
the alternating current signal calibration source to be tested is used for generating an analog voltage signal to be tested;
the first signal generator is used for respectively sending an external trigger signal and a sampling trigger signal to the reference voltage signal generation module and the sampling module, and simultaneously sending a phase locking signal to the to-be-tested alternating current signal calibration source to adjust the phase of the analog to-be-tested voltage signal;
the low end of the alternating current signal calibration source to be tested is electrically connected with the low end of the digital-to-analog converter, the first output port of the first signal generator is connected with the trigger port of the digital-to-analog converter through the first optical coupler isolation module, and the second output port of the first signal generator is electrically connected with the external phase locking port of the alternating current signal calibration source to be tested through the second optical coupler isolation module.
In one example, in the present invention, the sampling module includes:
the analog-to-digital converter is used for measuring the voltage value of each step of the analog reference voltage signal and measuring the voltage difference value of each step between the analog reference voltage signal and the analog voltage signal to be measured;
a second signal generator for transmitting a time-based signal to the analog-to-digital converter;
the trigger port of the analog-to-digital converter is electrically connected with the first output port of the first signal generator through the third optocoupler isolation module, the time base port of the analog-to-digital converter is electrically connected with the output port of the second signal generator, the high end of the analog-to-digital converter is electrically connected with the high end of the digital-to-analog converter, and the low end of the analog-to-digital converter is electrically connected with the high end of the calibration source of the alternating current signal to be tested.
In one example, in the present invention, further comprising:
the time base module is used for synchronizing the time of the digital-to-analog converter, the first signal generator and the second signal generator by sending time base signals, so that the reference voltage signal generation module, the voltage signal generation module to be tested and the sampling module realize time base synchronization;
the time base module is electrically connected with the digital-to-analog converter through the fourth optical coupling isolation module, is electrically connected with an external reference clock port of the first signal generator through the fifth optical coupling isolation module, and is electrically connected with an external reference clock port of the second signal generator through the sixth optical coupling isolation module.
In one example, in the present invention, the analog reference voltage signal is a sinusoidal step wave voltage signal of similar frequency and phase and amplitude to the analog voltage signal under test.
In one example, in the present invention, the analog voltage signal under test is a spectrally pure sine wave voltage signal.
Specifically, the low-frequency alternating voltage precise differential measurement system comprises: the reference voltage signal generating module comprises a digital-to-analog converter, and a digital-to-analog converter with resolution of 16 bits is selected, for example: an NI 6733 digital-analog converter for generating a sine step wave voltage signal with the same frequency and the same phase as the calibration source of the alternating current signal to be tested and with the approximate amplitude; the voltage signal generating module to be tested comprises a first signal generator and an alternating current signal calibration source to be tested, wherein the alternating current signal calibration source to be tested is a calibration source with higher signal stability and spectral purity, and the phase of a waveform to be tested can be adjusted through an external phase locking function, such as a Fluke 5720 alternating current signal calibration source, so as to generate a sine wave voltage signal to be tested; the sampling module comprises a second signal generator and an analog-to-digital converter, wherein the analog-to-digital converter is a double-integration analog-to-digital converter with good linearity and high measurement accuracy, such as an Agilent3458A analog-to-digital converter; the first and second signal generators are two-way synchronizable arbitrary waveform generators; the low end of the alternating current signal calibration source to be tested is electrically connected with the low end of the digital-to-analog converter, the time base port of the analog-to-digital converter is electrically connected with the output port of the second signal generator, the high end of the analog-to-digital converter is electrically connected with the high end of the digital-to-analog converter, and the low end of the analog-to-digital converter is electrically connected with the high end of the alternating current signal calibration source to be tested;
the system also comprises a plurality of optical coupling isolation modules which play a role in isolating signals; the optical coupler is unidirectionally transmitted, so that unidirectional transmission of signals can be realized, electric isolation between the input end and the output end is completely realized, the output signals have no influence on the input end, the anti-interference capability is strong, and the work is stable; the first output port of the first signal generator is connected with the trigger port of the digital-to-analog converter through the first optocoupler isolation module, the second output port of the first signal generator is electrically connected with the external phase locking port of the alternating current signal calibration source to be tested through the second optocoupler isolation module, the trigger port of the analog-to-digital converter is electrically connected with the first output port of the first signal generator through the third optocoupler isolation module, namely, the trigger signal generated by the first signal generator is respectively sent to the digital-to-analog converter and the analog-to-digital converter through the first optocoupler isolation module and the third optocoupler isolation module, and the phase locking signal generated by the first signal generator is sent to the alternating current signal calibration source to be tested through the second optocoupler isolation module;
the system also comprises a time base module, for example, a rubidium clock is selected, the time base module is electrically connected with an external time base port of the digital-to-analog converter through a fourth optical coupler isolation module, the time base module is electrically connected with an external reference clock port of the first signal generator through a fifth optical coupler isolation module, the time base module is electrically connected with an external reference clock port of the second signal generator through a sixth optical coupler isolation module, time base signals sent by the time base module are respectively sent to the digital-to-analog converter, the first signal generator and the second signal generator through the fourth optical coupler isolation module, the fifth optical coupler isolation module and the sixth optical coupler isolation module, so that the time of the digital-to-analog converter, the first signal generator and the second signal generator are synchronized, and the second signal generator sends the time base signals to the analog-to-digital converter again, so that the time of the system is synchronized; for example, all 10MHz reference time base of the system is provided by an external rubidium clock, and then the second signal generator provides 20MHz time base for the modified analog-to-digital converter;
the voltage measurement of the low-frequency alternating current signal is carried out by using a commercial DAC to replace a PJVS, firstly, the step voltage generated by the commercial DAC is accurately measured, and the voltage value of each step is measured;
then, the system is used for voltage differential measurement, a digital-to-analog converter generates a sine step wave voltage signal which has the same frequency and phase as the AC signal calibration source to be measured and has an approximate amplitude, an analog-to-digital converter is used for sampling the voltage difference signals generated by the digital-to-analog converter, the voltage difference of each step is measured, and the voltage difference and the voltage value of each step are added to obtain a reconstructed signal; and performing discrete Fourier transform on the reconstructed signal to obtain the to-be-detected waveform amplitude and phase information of the analog to-be-detected voltage signal.
The invention is further described below with reference to the drawings and specific examples, which are not intended to be limiting. It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
Example 1
As shown in fig. 2, the present embodiment provides a low-frequency ac voltage precise differential measurement system, including:
a reference voltage signal generation module comprising: the digital-to-analog converter 1 is used for generating an analog reference voltage signal, namely the digital-to-analog converter 1 generates a sine step wave voltage signal which has the same frequency and phase as the AC signal calibration source 3 to be tested and has an approximate amplitude;
wherein, the digital-to-analog converter 1 selects 16bit NI 6733 digital-to-analog converter;
the voltage signal to be measured generation module includes: the alternating current signal to be tested calibrates the source 3 and the first signal generator 4, is used for producing the analog voltage signal to be tested; the method comprises the steps that an alternating current signal to be measured calibration source 3 generates a sine wave voltage signal to be measured, wherein the sine wave voltage signal to be measured is high in signal stability and spectral purity;
wherein, the AC signal calibration source 3 to be measured is Fluke 5720;
a sampling module, comprising: the analog-to-digital converter 2 and the second signal generator 5 are used for sampling the reference voltage signal and measuring the voltage of each step; sampling a voltage difference signal between an analog reference voltage signal and an analog voltage signal to be detected to measure the voltage difference of each step;
wherein, the analog-to-digital converter 2 is an Agilent3458A double-integration analog-to-digital converter;
a time base module 12 for providing a time base signal of 10MHz to synchronize the time of the reference voltage signal generating module, the voltage signal to be measured generating module and the sampling module;
wherein, the time base module 12 selects rubidium clock;
the plurality of optocoupler isolation modules comprise a first optocoupler isolation module 6, a second optocoupler isolation module 7, a third optocoupler isolation module 8, a fourth optocoupler isolation module 9, a fifth optocoupler isolation module 6 and a sixth optocoupler isolation module 11;
the Ch.1 port of the first signal generator 4 is connected with the triggering port of the digital-to-analog converter 1 through the first optocoupler isolation module 6, the Ch.2 port of the first signal generator 4 is electrically connected with the external phase locking port of the alternating current signal calibration source 3 to be tested through the second optocoupler isolation module 7, the triggering port of the analog-to-digital converter 2 is electrically connected with the Ch.1 port of the first signal generator 4 through the third optocoupler isolation module 8, the time base port of the analog-to-digital converter 2 is electrically connected with the output port of the second signal generator 5, the H end of the analog-to-digital converter 2 is electrically connected with the H end of the digital-to-analog converter 1, the L end of the analog-to-digital converter 2 is electrically connected with the L end of the digital-to-analog converter 1, the time base module 12 is electrically connected with the digital-to-analog converter 1 through the fourth optocoupler isolation module 9, the time base module 12 is electrically connected with the external reference clock port of the first signal generator 4 through the fifth optocoupler isolation module 10, and the module 12 is electrically connected with the external reference clock port of the second signal generator 5 through the sixth optocoupler isolation module 11;
the step wave voltage signal generated by the digital-analog converter 1 is accurately measured through the analog-digital converter 2, and the voltage value of each step is obtained;
after the measurement is completed, the system is connected according to fig. 2, and the time of the whole measurement system is synchronized by transmitting a 10MHz time base signal through the time base module 12, wherein the second signal generator 5 provides a 20MHz time base signal to the analog-to-digital converter 2 according to the 10MHz time base signal; the first signal generator 4 sends an external trigger signal and a sampling trigger signal of a sine wave of 5Vpp to the digital-to-analog converter 1 and the analog-to-digital converter 2 through a ch.1 port, as shown by a signal b in fig. 3, the two signals are in phase with a voltage signal to be measured in the same frequency and are used for triggering a digital reference voltage signal conversion function and a sampling function outside the digital-to-analog converter 1 and the analog-to-digital converter 2 respectively, and sends a phase locking signal with the same frequency as the external trigger signal and the sampling trigger signal to the alternating-current signal calibration source 3 through a ch.2 port, as shown by a signal a in fig. 3, and is used for adjusting the phase of an analog voltage signal to be measured generated by the alternating-current signal calibration source 3 to be measured;
the digital-to-analog converter 1 generates a sine step wave voltage signal which has the same frequency and phase as the AC signal calibration source 3 to be tested and has an approximate amplitude, as shown by a signal c in fig. 3; the AC signal calibration source 3 to be tested generates a sine wave voltage signal to be tested with higher signal stability and spectral purity, as shown by a signal d in fig. 3, the voltage difference signals generated by the two signals are sampled by the analog-to-digital converter 2, and the voltage difference of each step is measured; and adding the voltage difference value and the voltage value of each step to obtain a reconstructed signal, and performing Discrete Fourier Transform (DFT) on the reconstructed signal to obtain the amplitude and phase information of the voltage signal to be detected.
Example 2
As shown in fig. 4, the embodiment provides a precise differential measurement method of low-frequency ac voltage, which includes:
the high end of the reference voltage signal generating module is electrically connected with the high end of the sampling module, the low end of the reference voltage signal generating module is electrically connected with the low end of the sampling module, and then the sampling module is used for sampling the analog reference voltage signal generated by the reference voltage signal generating module, so as to measure the voltage value of each step;
after the measurement is completed, the high end of the reference voltage signal generating module is electrically connected with the high end of the sampling module, the low end of the reference voltage signal generating module is electrically connected with the low end of the voltage signal generating module to be measured, the low end of the sampling module is electrically connected with the high end of the voltage signal generating module to be measured, and then the voltage difference signal between the analog reference voltage signal and the analog voltage signal to be measured is sampled through the sampling module, so that the voltage difference value of each step is measured;
adding the voltage difference value and the voltage value of each step to obtain a reconstructed signal; and performing discrete Fourier transform on the reconstructed signal to obtain the amplitude and phase information of the waveform to be tested of the analog voltage signal to be tested.
The voltage measurement of the low-frequency alternating current signal is carried out by using the commercial DAC to replace the PJVS, and the step voltage generated by the commercial DAC is accurately measured first. The step wave voltage signal generated by the digital-analog converter 1 is accurately measured by the analog-digital converter 2, and the voltage value of each step is obtained, which comprises the following specific steps:
s1: evaluating the time required for the transition of the digital-to-analog converter 1, measuring to remove the flat part of the transition;
s2: measuring the 0-bit voltage value of the analog-to-digital converter 2 in the DCV mode;
s3: the digital-to-analog converter 1 is connected with the analog-to-digital converter 2, each step voltage value of the digital-to-analog converter 1 is measured in the DCV mode, the corresponding 0 bit value is subtracted, and the measuring time of one point of each step is 0.1s.
From the manual of the analog-to-digital converter 2, its accuracy is 0.6ppm within 24 hours, the effect on measurement uncertainty on the ppm level is negligible; it is therefore necessary to carefully evaluate the influence of the drift amount of the digital-to-analog converter 1 on the measurement result; because the measurement result of the embodiment targets at the ppm level, the time of the digital-to-analog converter 1 at the ppm level drift amount is analyzed, if the accuracy of the ppm level is required, after the measurement is completed in the time, the step voltage values of the step wave are required to be measured again, and the next measurement can be performed;
after accurately measuring the step wave voltage, wiring is performed according to fig. 2 in embodiment 1, and then differential measurement is performed according to a low-frequency ac voltage precise differential measurement method of the present embodiment.
In order to ensure the consistency of the influence of noise on the measurement result, the equivalent time of the differential measurement of the aperture time ratio of each step of the analog-to-digital converter 2 to the previous step measurement is required to be ensured to be consistent; ending the measurement within the step voltage drift amount ppm level time, and measuring the zero voltage value of the analog-digital converter 2; after the input and output of the analog-to-digital converter 2 are replaced, the measurement is performed again to eliminate the influences of zero offset, lead voltage, thermoelectric voltage and the like; taking an average value under the measurement of the aperture time as 1 group of data with the equivalent voltage integration time of each step difference value of 0.1s of each aperture time; subtracting zero offset of the analog-to-digital converter 2 from each group of data, and multiplying the zero offset by a gain correction coefficient of the analog-to-digital converter in the measuring range to obtain a corrected measuring difference value; adding the corresponding step wave voltage value to the measured difference value, performing DFT conversion and performing Sinc compensation on the result to obtain the fundamental wave amplitude of the waveform to be measured under different aperture time; and taking an average value of the two voltage differential measurement results of the reversing to obtain a final measurement result.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described.
Claims (6)
1. A low frequency ac voltage precision differential measurement system comprising:
the reference voltage signal generation module is used for generating an analog reference voltage signal;
the voltage signal generating module to be tested is used for generating an analog voltage signal to be tested;
the sampling module is used for sampling the reference voltage signal and measuring the voltage of each step; sampling a voltage difference signal between the analog reference voltage signal and the analog voltage signal to be detected, and measuring the voltage difference of each step; adding the voltage difference value and the voltage value of each step to obtain a reconstructed signal; performing discrete Fourier transform on the reconstructed signal to obtain the waveform amplitude and phase information to be detected of the analog voltage signal to be detected;
the optocoupler isolation modules are connected between the voltage signal generation module to be tested, the reference voltage signal generation module and the sampling module;
the reference voltage signal generation module includes:
a digital-to-analog converter for converting an external digital reference voltage signal into the analog reference voltage signal;
the voltage signal to be measured generating module comprises:
the alternating current signal calibration source to be tested is used for generating the analog voltage signal to be tested;
the first signal generator is used for respectively transmitting an external trigger signal and a sampling trigger signal to the reference voltage signal generation module and the sampling module, and simultaneously transmitting a phase locking signal to the alternating current signal calibration source to be tested to adjust the phase of the analog voltage signal to be tested;
the low end of the alternating current signal calibration source to be tested is electrically connected with the low end of the digital-to-analog converter, a first output port of the first signal generator is connected with a trigger port of the digital-to-analog converter through the first optical coupling isolation module, and a second output port of the first signal generator is electrically connected with an external phase locking port of the alternating current signal calibration source to be tested through the second optical coupling isolation module.
2. The precision differential measurement system of low frequency ac voltage according to claim 1, wherein said sampling module comprises:
the analog-to-digital converter is used for measuring the voltage value of each step of the analog reference voltage signal and measuring the voltage difference value of each step between the analog reference voltage signal and the analog voltage signal to be measured;
a second signal generator for transmitting a time-based signal to the analog-to-digital converter;
the trigger port of the analog-to-digital converter is electrically connected with the first output port of the first signal generator through the third optocoupler isolation module, the time base port of the analog-to-digital converter is electrically connected with the output port of the second signal generator, the high end of the analog-to-digital converter is electrically connected with the high end of the digital-to-analog converter, and the low end of the analog-to-digital converter is electrically connected with the high end of the calibration source of the alternating current signal to be tested.
3. The low frequency ac voltage precision differential measurement system according to claim 2, further comprising:
the time base module is used for synchronizing the time of the digital-to-analog converter, the first signal generator and the second signal generator by sending time base signals, so that the reference voltage signal generation module, the voltage signal generation module to be tested and the sampling module realize time base synchronization;
the time base module is electrically connected with the digital-to-analog converter through a fourth optical coupling isolation module, the time base module is electrically connected with an external reference clock port of the first signal generator through a fifth optical coupling isolation module, and the time base module is electrically connected with an external reference clock port of the second signal generator through a sixth optical coupling isolation module.
4. The system of claim 1, wherein the analog reference voltage signal is a sinusoidal step wave voltage signal of similar frequency and phase and amplitude to the analog voltage signal to be measured.
5. The system of claim 1, wherein the analog voltage signal to be measured is a spectrally pure sine wave voltage signal.
6. A low frequency ac voltage precision differential measurement method based on the low frequency ac voltage precision differential measurement system of any one of claims 1-5, comprising:
the method comprises the steps that the high end of a reference voltage signal generating module is electrically connected with the high end of a sampling module, the low end of the reference voltage signal generating module is electrically connected with the low end of the sampling module, and then the sampling module is used for sampling an analog reference voltage signal generated by the reference voltage signal generating module, so that the voltage value of each step is measured;
after the measurement is completed, the high end of the reference voltage signal generating module is electrically connected with the high end of the sampling module, the low end of the reference voltage signal generating module is electrically connected with the low end of the voltage signal generating module to be measured, the low end of the sampling module is electrically connected with the high end of the voltage signal generating module to be measured, and then the voltage difference signal between the analog reference voltage signal and the analog voltage signal to be measured is sampled through the sampling module, so that the voltage difference of each step is measured; adding the voltage difference value and the voltage value of each step to obtain a reconstructed signal; and performing discrete Fourier transform on the reconstructed signal to obtain the to-be-detected waveform amplitude and phase information of the analog to-be-detected voltage signal.
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