CN114236454B - Error calibration method and device for broadband resistor divider - Google Patents
Error calibration method and device for broadband resistor divider Download PDFInfo
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Abstract
The invention relates to an error calibration method and device of a broadband resistor voltage divider. The method comprises the following steps: s1, providing a plurality of levels of voltage signals for the broadband resistor divider of a plurality of levels through a plurality of first channels and a plurality of second channels by utilizing a plurality of multifunctional standard sources; s2, when the multifunctional standard sources provide voltage signals of each level, the first channel is provided with a wideband resistor divider of the previous level, and the second channel is provided with a wideband resistor divider of the current level; s3, respectively receiving and sampling the partial pressure signals of the first channels and the partial pressure signals of the second channels by utilizing a plurality of digital sampling systems; s4, obtaining a net ratio difference and a net angle difference according to the ratio difference and the angle difference of the partial pressure signals of the first channels and the ratio difference and the angle difference of the partial pressure signals of the second channels. The invention can improve the accuracy and precision of the ratio difference and angle difference calibration of the broadband resistor divider.
Description
Technical Field
The invention relates to the technical field of metering, in particular to an error calibration method and device of a broadband resistor divider.
Background
The proportional metering has very important function in the electrical metering, and mainly can solve the problem of range expansion. Since the measurement standard or the measuring instrument usually has high accuracy only in a certain range, accurate measurement of a large range of electrical values is realized by a proportional device. The proportioner is usually made into an accessory type special proportioner or a proportioner standard device as a range extender of various measuring devices. The proportion standard device is adopted, so that the measuring instrument can be unified into a standard form, the structure is simple and reliable, the measuring accuracy is higher than that of a direct instrument, the insulation performance of a circuit can be improved, and the safety of the measuring instrument and a user is protected. With the development of measurement technology, the original proportion device serving as an accessory can be made to be higher in accuracy than the measurement instrument, so that the proportion device can serve as a main standard device and be matched with an auxiliary measurement instrument to complete testing work.
In the field of modern electrical precision measurement, it is very common to use the ratio and the ratio relation to achieve the purpose of measurement. Many precision meters rely on voltage ratios and current ratios for metering. The voltage proportional devices, the current divider, the variable resistor, the variable capacitor, the bridge and the attenuator are designed according to the principle of proportion. Calibration and calibration of the inductive voltage divider, the bridge proportional arm, the strain gauge attenuator and the like all require the accurate measurement of the proportional standard.
The AC resistor voltage divider is an important electromagnetic device, is mainly used for extending the range of AC voltage and is a necessary device for widening the measuring range of AC voltage. The AC proportional voltage divider is applicable to all AC voltage measuring instruments including AC voltage sources, AC voltmeters, AC-DC converters, measurement amplifiers, phase meters and the like. The precise AC voltage and power measurement is either the sampling AC/DC thermoelectric comparison method or the AC sampling measurement method, and the measured AC voltage must be attenuated into a voltage which can be directly accepted by a digital collector or a thermoelectric converter through an AC voltage divider. The broadband alternating current source technology is widely applied to the research and production test process of national defense and military equipment, and broadband alternating current voltage can reach the alternating current-direct current conversion standard through an alternating current voltage divider.
The calibration of the broadband resistor divider is always a difficult problem in the field of electrical measurement, and the difficulty is that the calibration of high accuracy ratio difference and angle difference is not established in China, a perfect calibration system of the broadband resistor divider is not established, the measurement standard of a broadband resistor divider calibration device is not established, and the calibration standard of the broadband resistor divider is not mature. The mechanism and unit for developing the broadband resistor divider calibration method and the calibration device are fewer. The DC voltage ratio difference is calibrated firstly, the AC-DC difference is calibrated again, and the angle difference cannot be calibrated.
Chinese patent ZL2016108844939 discloses an ac resistor voltage divider correction method based on an equivalence principle to build an error model. The patent proposes an alternating current resistor voltage divider correction method based on an equivalence principle to establish an error model, which comprises the steps of establishing a frequency error equivalence model of the alternating current resistor voltage divider, and completing analysis of errors of the alternating current resistor voltage divider in a frequency range of 50 Hz-100 kHz by using the model. Chinese patent ZL201510999332X discloses a self-calibrating resistor divider. The patent proposes a self-calibration method of a resistor voltage divider, and accurate calibration of the resistor voltage divider is realized by a segment-by-segment comparison method of a main voltage divider and a reference voltage divider. The technology is limited by a reference inductive voltage divider, the calibration frequency range is narrow, the voltage is low, and only downward transmission of the ratio difference of the resistor voltage divider under alternating current low voltage can be ensured.
Disclosure of Invention
In order to make the measurement accuracy of the ratio difference and the angle difference of the broadband resistor divider high, the invention provides an error calibration method and device of the broadband resistor divider.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
the invention provides an error calibration method of a broadband resistor voltage divider, which comprises the following steps:
s1, providing a plurality of levels of voltage signals for the broadband resistor divider of a plurality of levels through a plurality of first channels and a plurality of second channels by utilizing a plurality of multifunctional standard sources;
s2, when the multifunctional standard sources provide voltage signals of each level, the first channel is provided with a wideband resistor divider of the previous level, and the second channel is provided with a wideband resistor divider of the current level;
s3, respectively receiving and sampling the partial pressure signals of the first channels and the partial pressure signals of the second channels by utilizing a plurality of digital sampling systems;
s4, obtaining a net ratio difference and a net angle difference according to the ratio difference and the angle difference of the partial pressure signals of the first channels and the ratio difference and the angle difference of the partial pressure signals of the second channels.
According to one aspect of the invention, prior to the step S1, a voltage signal is provided to the digital sampling system by using a multifunctional standard source through a first channel and a second channel, respectively, so as to correct zero point errors of the digital sampling system.
According to one aspect of the present invention, the step S3 further includes: and compensating errors of non-whole period sampling of the digital sampling systems by using a non-whole period compensation algorithm in the process of respectively receiving and sampling the partial pressure signals of the first channels and the partial pressure signals of the second channels by using the digital sampling systems.
According to one aspect of the invention, the process of the non-integer period compensation algorithm comprises:
Establishing a mathematical model for an alternating current signal containing harmonic waves in the partial pressure signal, wherein the mathematical model comprises the following steps:
Wherein ω is angular frequency, T is a period of the divided signal, K is the number of harmonics, a 0 is a direct current component, a k and b k are harmonic components;
And performing non-integer period sampling on the alternating current signal by using the digital sampling system to obtain a discrete signal, wherein the discrete signal is:
wherein, the sampling interval is T s;
Processing the discrete signals by using a digital signal processing algorithm to obtain the frequency, amplitude and phase of each subharmonic signal, wherein, For the amplitude of the kth harmonic signal, arctan (a k/bk) is the phase of the kth harmonic signal;
the direct current component and each subharmonic component of the divided signal are obtained according to the frequency, amplitude and phase, and are compensated by the following formula,
Wherein a= (a 0,a1,a2,…,aK,b1,b2,…,bK)T represents a vector composed of a direct current component of the divided voltage signal and true values of each subharmonic component; the vector is composed of the direct current component and the estimated value of each subharmonic component obtained by utilizing the Fourier transformation principle under the sampling condition of the non-integer period;
Calculating sampling deviation of an irregular period by using an interpolation method, so that the sampling deviation of the irregular period meets |delta| < 1, and obtaining the complement of the sampling of the whole period as follows:
Wherein the sampling period is n+Δ, the end point of the sampling period is between n and n+l, the sampling point of the start point is y 0,y1 which is the first sampling point, and the two sampling points near the expected end point are y n and y n+l, respectively.
According to one aspect of the invention, the broadband resistor divider comprises a resistor main dividing part, a capacitor box and a buffer amplifier which are connected in sequence.
According to one aspect of the present invention, the upper wideband resistor divider is a 2V wideband resistor divider, a 4V wideband resistor divider, an 8V wideband resistor divider, a 16V wideband resistor divider, a 32V wideband resistor divider, a 64V wideband resistor divider, a 120V wideband resistor divider, a 240V wideband resistor divider, and a 480V wideband resistor divider;
the broadband resistor divider of the current stage is a 4V broadband resistor divider, an 8V broadband resistor divider, a 16V broadband resistor divider, a 32V broadband resistor divider, a 64V broadband resistor divider, a 120V broadband resistor divider, a 240V broadband resistor divider, a 480V broadband resistor divider and a 1000V broadband resistor divider.
According to one aspect of the invention, the voltage signal output by the multifunction standard source and being the wideband resistive divider is 0.8V, 2V, 4V, 8V, 16V, 32V, 64V, 120V, 240V and 480V.
The invention also provides an error calibration device of the broadband resistor divider, which is realized by the error calibration method of the broadband resistor divider, and comprises the following steps: a multifunctional standard source, a first broadband resistor divider, a second broadband resistor divider, a first digital sampling system and a second digital sampling system,
The first broadband resistor divider is provided with a first channel, and the second broadband resistor divider is provided with a second channel;
the first broadband resistor divider is connected with the first digital sampling system through the first channel, and the second broadband resistor divider is connected with the second digital sampling system through the second channel;
The multi-functional standard source provides voltage signals for the first wideband resistor divider and the second wideband resistor divider through the first channel and the second channel respectively.
According to another aspect of the invention, the first digital sampling system and the second digital sampling system each comprise: 3458A digital sampling module, PXIe chassis, controller, PXI-5421 signal generating module, GPIB control module and GPIB line,
The PXIe case, the controller and the PXI-5421 signal generating module jointly control two 3458A digital sampling modules to synchronously sample;
the GPIB lines are used for sequentially connecting the 3458A digital sampling module, the PXIe machine case, the controller, the PXI-5421 signal generating module and the GPIB control module.
According to another aspect of the invention, the first digital sampling system and the second digital sampling system each comprise: PXI-5922 digital sampling module, PXIe-6674T clock module, GPIB control module, GPIB line, PXIe cabinet and controller,
The PXIe-6674T clock module is used for enabling the sampling time interval of the two PXI-5922 digital sampling modules to be more accurate;
the GPIB lines sequentially connect the PXI-5922 digital sampling module, the PXIe chassis, the controller, the PXIe-6674T clock module and the GPIB control module.
The beneficial effects are that:
According to the scheme of the invention, aiming at the tracing problem of the broadband (10 Hz-1 MHz) resistor divider, a low-frequency resistor divider error calibration device (10 Hz-1 kHz) based on 3458A and a high-frequency resistor divider error calibration device (1 kHz-1 MHz) based on PXI-5922 are provided, the measuring frequency of the resistor divider is expanded to 1MHz, and the repeatability and the stability of the broadband resistor divider calibration are improved.
Aiming at the impedance network and matching problem of the broadband resistor divider, the idea of regarding the buffer amplifier for impedance transformation as a component part of the broadband resistor divider and carrying out integral error calibration on the resistor dividing part, the capacitor box and the buffer amplifier of the resistor divider is provided. The wideband resistor divider can be calibrated and the measurement accuracy of the wideband resistor divider is improved.
Aiming at the problems of jitter of a sampling time base and the asynchronous problem of a sampling signal and a measuring signal, a non-whole period compensation algorithm is provided, a 3458A low-frequency device adopts a PXI-5421 signal generating card as an external synchronous sampling trigger device, a PXI-5922 high-frequency device adopts a PXIe-6674T clock card as an internal sampling clock, so that the sampling deviation of the whole period is smaller than 0.0002 sampling intervals, the repeatability is smaller than 0.0001 sampling intervals, the influence of the sampling error of the non-whole period is overcome, and the measuring repeatability of the alternating voltage proportion reaches 2X 10 -6.
In order to solve the traceability problem of the ratio difference and the angle difference value of the broadband resistor divider, the uncertainty of the calibration result is reduced, and the error calibration device of the high-frequency and low-frequency resistor divider is developed by comprehensively adopting various technical means of a frequency division calibration technology, a slow-release integral calibration technology, a full-range half-load recursive calibration technology, a synchronous sampling measurement technology and non-full-period sampling compensation.
Drawings
FIG. 1 schematically illustrates a flow chart of a method for error calibration of a wideband resistor divider according to one embodiment of the present invention;
FIG. 2 schematically illustrates an error calibration procedure of a wideband resistor divider according to an embodiment of the present invention;
FIG. 3 schematically illustrates an error calibration apparatus of a wideband resistor divider according to an embodiment of the present invention;
FIG. 4 schematically illustrates an error calibration apparatus based on a wideband resistive divider of 3458A in accordance with one embodiment of the present invention;
FIG. 5 schematically illustrates an error calibration apparatus based on a 5922 broadband resistive divider according to an embodiment of the present invention.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments will be briefly described below. It is apparent that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
The present invention will be described in detail below with reference to the drawings and the specific embodiments, which are not described in detail herein, but the embodiments of the present invention are not limited to the following embodiments.
Fig. 3 shows a calibration device for a broadband resistive divider according to the inventive concept. In the embodiment shown in fig. 3, the calibration device is composed of a multifunctional standard source (including an amplifier), two digital samplers with high stability elements, a case and a controller, a high-precision digital sampling card, a signal generating card, a clock card, a control card, a wire, a computer and the like. In this embodiment, the digital sampler is a 3458A digital sampler, the chassis is a PXIe chassis, the high-precision digital sampling card is a PXI-5922 high-precision digital sampling card, the signal generating card is a PXI-5421 signal generating card, the clock card is a PXIe-6674T clock card, the control card is a GPIB control card, and the line is a GPIB line.
As shown in FIG. 4, in the process of calibrating the ratio difference and the angle difference of 50Hz, 400Hz and 1kHz frequencies of the broadband resistor divider according to one embodiment of the invention, a low-frequency resistor divider calibrating device is composed of a multifunctional standard source (comprising an amplifier), two 3458A digital samplers with high-stability options, a PXIe case and a controller, a PXI-5421 signal generating card, a GPIB control card, a GPIB line and a computer. The PXIe chassis, the controller and the PXI-5421 signal generator are used as external trigger signals to control the two platforms 3458A to synchronously sample.
As shown in FIG. 5, in another embodiment according to the present invention, the calibration device for the high-frequency resistor divider is composed of a multifunctional standard source (including an amplifier), a PXIe case and a controller, a PXI-5922 high-precision digital sampling card, a PXIe-6674T clock card, a GPIB control card, a GPIB line and a computer when calibrating the ratio difference and the angle difference of the frequencies of 10kHz, 100kHz and 1MHz of the broadband resistor divider. The clock generated by the PXI-6674T clock card is used for replacing the internal sampling clock of the PXI-5922, so that the synchronization error of the PXI-5922 sampling is reduced.
In one embodiment according to the present invention, the whole set of voltage divider is designed based on two multiplying factors in order to increase the uncertainty of the index and calibration result of the voltage divider. Each voltage divider has a fixed voltage division ratio, 10 rated input voltages are respectively 2V, 4V, 8V, 16V, 32V, 64V, 120V, 240V, 480V and 1000V from large to small, output voltages are all 0.8V, high-range voltage is guaranteed to be twice as high as low-range voltage, input impedance is between 500 omega and 250k omega, working current is 4mA, an adjustable capacitor box is connected behind a main voltage division part in use, and a 1:1 buffer amplifier is connected to the rear end of the main voltage division part for impedance transformation. The main characteristics of each voltage divider are shown in table 1.
TABLE 1 broadband resistor divider characteristics
After the design and construction of the resistive divider for broadband according to the concepts of the present invention as described above, calibration is performed according to the following principles and concepts.
Since the output impedance of the broadband resistive divider is large, there is typically a resistor of several hundred ohms and a capacitor of several tens of picofarads to several hundred picofarads, which can introduce large errors if measured directly using broadband ac voltage measurement equipment. Thus, in one embodiment, a 1:1 buffer amplifier is back-ended for impedance transformation in accordance with the concepts of the present invention. In this embodiment, the buffer amplifier is considered to be part of a resistor divider. On the basis, the whole error calibration is carried out on the resistor voltage division part, the capacitor box and the buffer amplifier. Each voltage divider has a capacitor box matched with the voltage divider and a buffer amplifier used fixedly.
In order to reduce the errors introduced by different ranges of the digital sampler and reduce the nonlinear errors of the same range, in the embodiment, the input voltage of the broadband resistor divider adopts a two-multiplying-power design, namely, the rated input voltage of one voltage divider is twice the rated input voltage of the other voltage divider, and the rated input voltage of the initial voltage divider is reduced to 2V.
The voltage divider with the two-multiplying power design can be calibrated through a half-voltage load recursion method, namely, the 2V/0.8V voltage divider is calibrated from the same 0.8V signal by means of a 3458A/PXI-5922 high-precision digital sampling system, then the 4V/0.8V is calibrated under half-load voltage by using the 2V/0.8V, after the 4V/0.8V is determined, the 8V/0.8V is calibrated under half-load voltage, and the steps are sequentially recursion to 480V/0.8V. In the calibration process, the CH0 channel is always used as a reference, and the CH1 channel is used as a measured. The calibration software is programmed by LabVIEW language, and the operation process is based on a non-integer period compensation algorithm. Calibration of the starting voltage divider 2V/0.8V relies on the 3458A/PXI-5922 high precision digital sampling system to ensure good linearity at full-scale and half-scale points. The calibration procedure takes advantage of this natural criterion of a voltage ratio of 1:1 and a phase angle of 0 ° for the same signal.
Referring to fig. 1, the error calibration method of the wideband resistor divider of the present embodiment includes:
s1, providing a plurality of levels of voltage signals for a plurality of levels of broadband resistor voltage dividers through a plurality of first channels and a plurality of second channels by utilizing a plurality of multifunctional standard sources;
s2, when a plurality of multifunctional standard sources provide voltage signals of each level, a first channel is provided with a wideband resistor voltage divider of the previous level, and a second channel is provided with a wideband resistor voltage divider of the current level;
S3, respectively receiving and sampling partial pressure signals of a plurality of first channels and partial pressure signals of a plurality of second channels by utilizing a plurality of digital sampling systems;
S4, obtaining a net ratio difference and a net angle difference according to the ratio difference and the angle difference of the partial pressure signals of the first channels and the ratio difference and the angle difference of the partial pressure signals of the second channels.
The previous wideband resistor divider is a 2V wideband resistor divider, a 4V wideband resistor divider, an 8V wideband resistor divider, a 16V wideband resistor divider, a 32V wideband resistor divider, a 64V wideband resistor divider, a 120V wideband resistor divider, a 240V wideband resistor divider, and a 480V wideband resistor divider. The broadband resistor divider is a 4V broadband resistor divider, an 8V broadband resistor divider, a 16V broadband resistor divider, a 32V broadband resistor divider, a 64V broadband resistor divider, a 120V broadband resistor divider, a 240V broadband resistor divider, a 480V broadband resistor divider and a 1000V broadband resistor divider. The voltage signals output by the multifunctional standard source and used for the broadband resistor divider are 0.8V, 2V, 4V, 8V, 16V, 32V, 64V, 120V, 240V and 480V. The first channel and the second channel refer to a CH0 channel and a CH1 channel, respectively.
Referring to fig. 2, specific calibration steps are as follows:
Step 1: calibrating the zero point of the device. The multifunctional standard source outputs 0.8V voltage, is directly connected into CH0 and CH1 channels of a 3458A/PXI-5922 high-precision digital sampling system without a voltage divider, runs the system, records the ratio difference and the angle difference obtained by testing at the moment, and corrects zero point errors of the system.
Step 2: the 2V voltage divider is calibrated. The multifunctional standard source outputs 0.8V voltage, and one path of the voltage is directly connected into a CH0 channel of a 3458A/PXI-5922 high-precision digital sampling system without a voltage divider. The other path is connected to a CH1 channel of a 3458A/PXI-5922 high-precision digital sampling system through a 2V voltage divider, the system is operated, and the ratio difference and the angle difference obtained through testing at the moment are recorded, namely the ratio difference and the angle difference of the 2V voltage divider.
Step 3: the 4V voltage divider is calibrated. The multifunctional standard source outputs 2V voltage, and one path of the voltage passes through a 2V voltage divider and is connected into a CH0 channel of a 3458A/PXI-5922 high-precision digital sampling system. The other path is connected to a CH1 channel of a 3458A/PXI-5922 high-precision digital sampling system through a 4V voltage divider, the system is operated, the ratio difference and the angle difference obtained through testing at the moment are recorded, and after the ratio difference and the angle difference of the 2V voltage divider are corrected, the ratio difference and the angle difference of the 4V voltage divider can be obtained.
Step 4: the 8V voltage divider was calibrated. The multifunctional standard source outputs 4V voltage, and one path of the voltage passes through a 4V voltage divider and is connected into a CH0 channel of a 3458A/PXI-5922 high-precision digital sampling system. The other path is connected to a CH1 channel of a 3458A/PXI-5922 high-precision digital sampling system through an 8V voltage divider, the system is operated, the ratio difference and the angle difference obtained through testing at the moment are recorded, and after the ratio difference and the angle difference of the 4V voltage divider are corrected, the ratio difference and the angle difference of the 8V voltage divider can be obtained.
Step 5: the 16V voltage divider was calibrated. The multifunctional standard source outputs 8V voltage, and one path of the voltage passes through an 8V voltage divider and is connected into a CH0 channel of a 3458A/PXI-5922 high-precision digital sampling system. The other path is connected to a CH1 channel of a 3458A/PXI-5922 high-precision digital sampling system through a 16V voltage divider, the system is operated, the ratio difference and the angle difference obtained through testing at the moment are recorded, and the ratio difference and the angle difference of the 16V voltage divider can be obtained after the 8V voltage divider ratio difference and the angle difference are corrected.
Step 6: the 32V voltage divider is calibrated. The multifunctional standard source outputs 16V voltage, and one path of the voltage passes through a 16V voltage divider and is connected into a CH0 channel of a 3458A/PXI-5922 high-precision digital sampling system. The other path is connected to a CH1 channel of a 3458A/PXI-5922 high-precision digital sampling system through a 32V voltage divider, the system is operated, the ratio difference and the angle difference obtained through testing at the moment are recorded, and the ratio difference and the angle difference of the 32V voltage divider can be obtained after the ratio difference and the angle difference of the 16V voltage divider are corrected.
Step 7: the 64V voltage divider is calibrated. The multifunctional standard source outputs 32V voltage, and one path of the voltage passes through a 32V voltage divider and is connected into a CH0 channel of a 3458A/PXI-5922 high-precision digital sampling system. The other path is connected to a CH1 channel of a 3458A/PXI-5922 high-precision digital sampling system through a 64V voltage divider, the system is operated, the ratio difference and the angle difference obtained through testing at the moment are recorded, and the ratio difference and the angle difference of the 64V voltage divider can be obtained after the ratio difference and the angle difference of the 32V voltage divider are corrected.
Step 8: the 120V voltage divider is calibrated. The multifunctional standard source outputs 60V voltage, and one path of the voltage passes through a 64V voltage divider and is connected into a CH0 channel of a 3458A/PXI-5922 high-precision digital sampling system. The other path is connected to a CH1 channel of a 3458A/PXI-5922 high-precision digital sampling system through a 120V voltage divider, the system is operated, the ratio difference and the angle difference obtained through testing at the moment are recorded, and the ratio difference and the angle difference of the 120V voltage divider can be obtained after the 64V voltage divider ratio difference and the angle difference are corrected.
Step 9: the 240V voltage divider is calibrated. The multifunctional standard source outputs 120V voltage, and one path of the voltage passes through a 120V voltage divider and is connected into a CH0 channel of a 3458A/PXI-5922 high-precision digital sampling system. The other path is connected to a CH1 channel of a 3458A/PXI-5922 high-precision digital sampling system through a 240V voltage divider, the system is operated, the ratio difference and the angle difference obtained through testing at the moment are recorded, and after the ratio difference and the angle difference of the 120V voltage divider are corrected, the ratio difference and the angle difference of the 240V voltage divider can be obtained.
Step 10: the 480V voltage divider was calibrated. The multifunctional standard source outputs 240V voltage, and one path of the voltage passes through a 240V voltage divider and is connected into a CH0 channel of a 3458A/PXI-5922 high-precision digital sampling system. The other path is connected to a CH1 channel of a 3458A/PXI-5922 high-precision digital sampling system through a 480V voltage divider, the system is operated, the ratio difference and the angle difference obtained through the test at the moment are recorded, and after the ratio difference and the angle difference of the 240V voltage divider are corrected, the ratio difference and the angle difference of the 480V voltage divider can be obtained.
Step 11: the 1000V voltage divider is calibrated. The multifunctional standard source outputs 480V voltage, and one path of the voltage passes through a 480V voltage divider and is connected into a CH0 channel of a 3458A/PXI-5922 high-precision digital sampling system. The other path is connected to a CH1 channel of a 3458A/PXI-5922 high-precision digital sampling system through a 1000V voltage divider, the system is operated, the ratio difference and the angle difference obtained through testing at the moment are recorded, and after the 480V voltage divider ratio difference and the angle difference are corrected, the ratio difference and the angle difference of the 1000V voltage divider can be obtained.
According to the inventive concept, the effect of the non-integer period error is taken into account in the calibration process and the non-integer period is compensated for.
The non-integer period compensation algorithm according to the invention can be used for accurate measurement of alternating current signals. Compared with other algorithms in the prior art, the compensation algorithm still has higher measurement accuracy, and only 1 fundamental wave result is input during calculation.
For the measured alternating current signal, if N pieces of sampling data are used for analysis, when NT s =mt, the sampling process is called whole period sampling, where T s is a sampling interval (sampling frequency is f s＝1/Ts), T is a measured signal period, and M is an integer; when NT s +.mt, the sampling process is called non-integer period sampling. For non-integer period sampling, when NT s -mt=Δ, Δ+.0, and |Δ| < 1, it is referred to as quasi-integer period sampling, and more generally |Δ| < pi, this is referred to as non-integer period sampling. To improve the measurement accuracy of the ac sampling method, it is preferable to implement full-period sampling, but since the frequency of the measured signal always varies within a certain range in practice, the period cannot be accurately measured, and in practice, the digital sampling system cannot completely implement full-period sampling, and N sample data cannot completely cover the periods of M measured signals, that is, NT s -mt=Δ (herein, Δ is referred to as non-full-period sampling deviation). The non-integer period compensation algorithm brings the calculated non-integer period sampling deviation delta into a model, and corrects the primary result, so as to obtain a more accurate secondary result.
For an alternating current signal containing harmonics, the mathematical model is assumed to be
Wherein ω is angular frequency, T is the period of the signal, K is the number of harmonics, a 0 is the DC component,For the magnitude of the kth harmonic, arctan (a k/bk) is the phase of the kth harmonic. The discrete signal can be obtained by sampling y (T) with a digital sampling system with a sampling interval of T s (sampling frequency f s＝1/Ts):
The discrete signals are analyzed by adopting a certain digital signal processing algorithm, and parameters such as frequency, amplitude, phase and the like of each subharmonic can be obtained.
Regarding the time-domain continuous signal in equation (1), the parameters of the direct current component and the nth harmonic are known as follows, based on the orthogonality of the trigonometric function and the fourier transform principle:
if the digital sampling system performs full-period sampling, i.e., NT s =mt, then the same applies according to the orthogonality of the trigonometric functions and the fourier transform principle
By adopting the non-whole period sampling method, the non-whole period sampling deviation reaches |delta| < 1, and the quasi-whole period sampling is realized. NT s = MT + delta under quasi-integer period sampling conditions. Still using fourier transform principles to analyze harmonics, then
If it is
Then equation (10) can be written as
Similarly, the parameters of the nth harmonic can be described as follows:
The rewrites (11) to (13) are as follows:
the vector consisting of the true values of the direct current component and each subharmonic component of the measured signal is assumed to be:
A＝(a0,a1,a2,…,aK,b1,b2,…,bK)T (15)
under the condition of non-integer period sampling, the vector formed by the direct current component and the estimated value of each subharmonic component obtained by utilizing the Fourier transformation principle is
Order the
Then according to equation (14) it is possible to obtain
Obviously, if known under non-full period sampling conditionsAnd F, the DC component and harmonic component of the detected signal can be compensated by the following formula
The (2K+1) x (2K+1) dimensional matrix F can be written in the following form
Wherein,
F11＝1
F12＝(F21)T＝(β1,β2,…,βK)
F13＝(F31)T＝(α1,α2,…,αK)
Calculating the sampling deviation delta of the non-whole period can be performed by adopting an interpolation method: assuming that the sampling period corresponds to n+Δ, the end of the period is between n and n+l, the starting point sample y 0、y1 is the first sampling point, the two sampling points near the expected end are y n and y n+l, and in addition to letting y 0 interpolate between y n and y n+l, letting y n+1 interpolate between y0 and y l, the complement Δ given for the whole period sample is:
The above description is only one embodiment of the present invention and is not intended to limit the present invention, and various modifications and variations of the present invention will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. An error calibration method for a broadband resistor divider, comprising:
s1, providing a plurality of levels of voltage signals for the broadband resistor divider of a plurality of levels through a plurality of first channels and a plurality of second channels by utilizing a plurality of multifunctional standard sources;
s2, when the multifunctional standard sources provide voltage signals of each level, the first channel is provided with a wideband resistor divider of the previous level, and the second channel is provided with a wideband resistor divider of the current level;
s3, respectively receiving and sampling the partial pressure signals of the first channels and the partial pressure signals of the second channels by utilizing a plurality of digital sampling systems;
s4, obtaining a net ratio difference and a net angle difference according to the ratio difference and the angle difference of the partial pressure signals of the first channels and the ratio difference and the angle difference of the partial pressure signals of the second channels;
the upper-stage broadband resistor divider is a 2V broadband resistor divider, a 4V broadband resistor divider, an 8V broadband resistor divider, a 16V broadband resistor divider, a 32V broadband resistor divider, a 64V broadband resistor divider, a 120V broadband resistor divider, a 240V broadband resistor divider and a 480V broadband resistor divider;
The broadband resistor divider of the current stage is a 4V broadband resistor divider, an 8V broadband resistor divider, a 16V broadband resistor divider, a 32V broadband resistor divider, a 64V broadband resistor divider, a 120V broadband resistor divider, a 240V broadband resistor divider, a 480V broadband resistor divider and a 1000V broadband resistor divider.
2. The method according to claim 1, characterized in that prior to said step S1, a voltage signal is provided to the digital sampling system by means of a multi-functional standard source via a first channel and a second channel, respectively, and the zero point error of the digital sampling system is corrected.
3. The method according to claim 1, wherein the step S3 further comprises: and compensating errors of non-whole period sampling of the digital sampling systems by using a non-whole period compensation algorithm in the process of respectively receiving and sampling the partial pressure signals of the first channels and the partial pressure signals of the second channels by using the digital sampling systems.
4. A method according to claim 3, wherein the process of the non-integer period compensation algorithm comprises:
Establishing a mathematical model for an alternating current signal containing harmonic waves in the partial pressure signal, wherein the mathematical model comprises the following steps:
Wherein ω is angular frequency, T is a period of the divided signal, K is the number of harmonics, a 0 is a direct current component, a k and b k are harmonic components;
And performing non-integer period sampling on the alternating current signal by using the digital sampling system to obtain a discrete signal, wherein the discrete signal is:
wherein, the sampling interval is T s;
Processing the discrete signals by using a digital signal processing algorithm to obtain the frequency, amplitude and phase of each subharmonic signal, wherein, For the amplitude of the kth harmonic signal, arctan (a k/bk) is the phase of the kth harmonic signal;
the direct current component and each subharmonic component of the divided signal are obtained according to the frequency, amplitude and phase, and are compensated by the following formula,
Wherein a= (a 0,a1,a2,…,aK,b1,b2,…,bK)T represents a vector composed of a direct current component of the divided voltage signal and true values of each subharmonic component; the vector is composed of the direct current component and the estimated value of each subharmonic component obtained by utilizing the Fourier transformation principle under the sampling condition of the non-integer period;
Calculating the sampling deviation of the non-integer period by using an interpolation method, so that the sampling deviation of the non-integer period meets the delta <1, and obtaining the complement of the sampling of the integer period as follows:
Wherein the sampling period is n+delta, the end point of the sampling period is between n and n+l, the sampling point of the starting point is y 0,y1 which is the first sampling point, and the two sampling points near the expected end point are y n and y n+l respectively.
5. The method of claim 1, wherein the broadband resistive divider comprises a resistive main dividing section, a capacitor box, and a buffer amplifier connected in sequence.
6. The method of claim 1, wherein the voltage signal output by the multifunction standard source and being the wideband resistive divider is 0.8V, 2V, 4V, 8V, 16V, 32V, 64V, 120V, 240V, and 480V.
7. An error calibration apparatus of a wideband resistor divider implemented by the error calibration method of any one of claims 1 to 6, comprising: a multifunctional standard source, a first broadband resistor divider, a second broadband resistor divider, a first digital sampling system and a second digital sampling system,
The first broadband resistor divider is provided with a first channel, and the second broadband resistor divider is provided with a second channel;
the first broadband resistor divider is connected with the first digital sampling system through the first channel, and the second broadband resistor divider is connected with the second digital sampling system through the second channel;
The multi-functional standard source provides voltage signals for the first wideband resistor divider and the second wideband resistor divider through the first channel and the second channel respectively.
8. The apparatus of claim 7, wherein the first digital sampling system and the second digital sampling system each comprise: 3458A digital sampling module, PXIe chassis, controller, PXI-5421 signal generating module, GPIB control module and GPIB line,
The PXIe case, the controller and the PXI-5421 signal generating module jointly control two 3458A digital sampling modules to synchronously sample;
the GPIB lines are used for sequentially connecting the 3458A digital sampling module, the PXIe machine case, the controller, the PXI-5421 signal generating module and the GPIB control module.
9. The apparatus of claim 7, wherein the first digital sampling system and the second digital sampling system each comprise: PXI-5922 digital sampling module, PXIe-6674T clock module, GPIB control module, GPIB line, PXIe cabinet and controller,
The PXIe-6674T clock module is used for enabling the sampling time interval of the two PXI-5922 digital sampling modules to be more accurate;
the GPIB lines sequentially connect the PXI-5922 digital sampling module, the PXIe chassis, the controller, the PXIe-6674T clock module and the GPIB control module.
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