CN219349111U - Ultra-low error high-precision measurement system for dual-channel voltage signal source - Google Patents
Ultra-low error high-precision measurement system for dual-channel voltage signal source Download PDFInfo
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Abstract
The application discloses a binary channels voltage signal source ultra-low error high accuracy measurement system. The system comprises: the channel switching module composed of the high-speed precise analog switches is used for realizing the mutual switching of the differential signals of the tested voltage signals and the standard voltage signals of the two channels of the data acquisition module according to the preset switching frequency, realizing the impedance matching of the differential signals of the tested voltage signals or the standard voltage signals through the preset four precise buffers, carrying out differential mode amplification on the tested voltage signals or the standard voltage signals through the first high-precision operational amplifier module and the second high-precision operational amplifier module, filtering the tested voltage signals or the standard voltage signals through the first filter and the second filter, converting the received standard voltage signals and the tested voltage signals into the tested voltage digital signals and the standard voltage digital signals through the data acquisition module of the digitizer, and carrying out error calculation according to the tested voltage digital signals and the standard voltage digital signals.
Description
Technical Field
The application relates to the technical field of electronic metering, in particular to a double-channel voltage signal source ultra-low error high-precision measurement system.
Background
According to the requirements of metering methods and various management standards, the strong detection metering device of the current transformer is required to be subjected to periodic verification or calibration according to law. The transformer calibrator is a special device for calibrating or calibrating the current transformer. When the traditional transformer calibrator works, a knob is manually rotated by a person to observe an alternating current zero indicator pointer, when the pointer approaches zero, the current angle difference and the ratio difference are recorded, or automatic zero setting and automatic calibration are realized through a software control voltage division process, but no matter which method is adopted, errors caused by different channel circuits exist at present (the two errors are the difference value of the fixed gain errors of the channels and the phase difference between the channels, and the errors can be additionally calculated into the error measurement result of the transformer). Under the background, a method and a device for dual-channel measurement are needed to solve the measurement deviation caused by inconsistent dual-channel gains of modules and improve the measurement accuracy.
Disclosure of Invention
Aiming at the problems in the prior art, the present disclosure provides a dual-channel voltage signal source ultra-low error high-precision measurement system.
According to one aspect of the present application, there is provided a dual channel voltage signal source ultra-low error high precision measurement system, comprising:
the channel switching module is composed of high-speed precise analog switches and is used for realizing the mutual switching of the differential signals of the tested voltage signals and the standard voltage signals of the two channels of the data acquisition module according to the preset switching frequency;
the first precision buffer, the second precision buffer, the third precision buffer and the fourth precision buffer are used for realizing impedance matching of a measured voltage signal or a differential signal of a standard voltage signal, and reducing the influence of a dual-channel error precision measurement system on the measured voltage signal;
the first high-precision operational amplifier module and the second high-precision operational amplifier module are used for carrying out differential mode amplification on the measured voltage signal or the standard voltage signal and converting the measured voltage signal into the range of the data acquisition module;
the first filter and the second filter are used for filtering the tested voltage signal or the standard voltage signal and outputting the filtered voltage signal or the standard voltage signal to the data acquisition module through the analog output interface;
the data acquisition module of the digitizer converts the received standard voltage signals and the detected voltage signals into detected voltage digital signals and standard voltage digital signals;
and the computing equipment is used for performing error computation according to the measured voltage digital signal and the standard voltage digital signal.
Optionally, the method further comprises: the first TVS and the surge protection module and the second TVS and the surge protection module are used for sending the differential signals of the tested voltage signal and the standard voltage signal to the channel switching module, so that the electrostatic breakdown of the subsequent devices is prevented.
Optionally, the method further comprises: and the external clock input interface is used for connecting an external clock source.
Optionally, the method further comprises: the clock selection channel is used for selecting whether the clock source of the synchronous sampling signal output to the data acquisition module is an external clock source or an internal clock source.
Optionally, the method further comprises: the clock management module is used for dividing the frequency of the external clock source, providing synchronous sampling signals for the channel switching module and the data acquisition module, and coordinating the working time sequence of the dual-channel error precision measurement system.
Optionally, the method further comprises: and the gain selection channel is used for determining the first high-precision operational amplifier module and the second high-precision operational amplifier module to attenuate or gain amplify the measured voltage signal and the standard voltage signal according to the range of the data acquisition module.
Therefore, the ultra-low error high-precision measurement system for the dual-channel voltage signal source provided by the utility model solves the measurement deviation caused by inconsistent dual-channel gain of the module based on the errors caused by different channel circuits in the verification measurement of the current voltage signal source, and improves the measurement precision.
The above, as well as additional objectives, advantages, and features of the present application will become apparent to those skilled in the art from the following detailed description of a specific embodiment of the present application when read in conjunction with the accompanying drawings.
Drawings
Some specific embodiments of the present application will be described in detail hereinafter by way of example and not by way of limitation with reference to the accompanying drawings. The same reference numbers will be used throughout the drawings to refer to the same or like parts or portions. It will be appreciated by those skilled in the art that the drawings are not necessarily drawn to scale. In the accompanying drawings:
FIG. 1 is a schematic diagram of a dual channel voltage signal source ultra-low error high precision measurement system according to an embodiment of the present application;
FIG. 2 is a timing diagram of a dual channel switching strategy according to an embodiment of the present application;
FIG. 3 is a simplified schematic diagram of a dual channel voltage signal source ultra-low error high precision measurement system according to an embodiment of the present application;
FIG. 4 is a schematic diagram of waveforms of a measured voltage signal source and a standard voltage signal source according to an embodiment of the present application;
FIG. 5 is a schematic waveform diagram of a channel switch according to an embodiment of the present application;
fig. 6 is a schematic diagram of a buffered, gain 0.5 filtered waveform after channel switching according to an embodiment of the present application.
Detailed Description
It should be noted that, without conflict, the embodiments of the present disclosure and features of the embodiments may be combined with each other. The present disclosure will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
In order that those skilled in the art will better understand the present disclosure, a technical solution in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present disclosure, not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without inventive effort, based on the embodiments in this disclosure, shall fall within the scope of the present disclosure.
It should be noted that the terms "first," "second," and the like in the description and claims of the present disclosure and in the foregoing figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the disclosure described herein are, for example, capable of operation in connection with other embodiments. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
FIG. 1 is a dual channel voltage signal source ultra-low error high precision measurement system according to an embodiment of the present application. Referring to fig. 1, the ultra-low error high-precision measurement system of the dual-channel voltage signal source comprises:
the channel switching module is composed of high-speed precise analog switches and is used for realizing the mutual switching of the differential signals of the tested voltage signals and the standard voltage signals of the two channels of the data acquisition module according to the preset switching frequency;
the first precision buffer, the second precision buffer, the third precision buffer and the fourth precision buffer are used for realizing impedance matching of a measured voltage signal or a differential signal of a standard voltage signal, and reducing the influence of a dual-channel error precision measurement system on the measured voltage signal;
the first high-precision operational amplifier module and the second high-precision operational amplifier module are used for carrying out differential mode amplification on the measured voltage signal or the standard voltage signal and converting the measured voltage signal into the range of the data acquisition module;
the first filter and the second filter are used for filtering the tested voltage signal or the standard voltage signal and outputting the filtered voltage signal or the standard voltage signal to the data acquisition module through the analog output interface;
the data acquisition module of the digitizer converts the received standard voltage signals and the detected voltage signals into detected voltage digital signals and standard voltage digital signals;
and the computing equipment is used for performing error computation according to the measured voltage digital signal and the standard voltage digital signal.
Optionally, the method further comprises: the first TVS and the surge protection module and the second TVS and the surge protection module are used for sending the differential signals of the tested voltage signal and the standard voltage signal to the channel switching module, so that the electrostatic breakdown of the subsequent devices is prevented.
Optionally, the method further comprises: and the external clock input interface is used for connecting an external clock source.
Optionally, the method further comprises: the clock selection channel is used for selecting whether the clock source of the synchronous sampling signal output to the data acquisition module is an external clock source or an internal clock source.
Optionally, the method further comprises: the clock management module is used for dividing the frequency of the external clock source, providing synchronous sampling signals for the channel switching module and the data acquisition module, and coordinating the working time sequence of the dual-channel error precision measurement system.
Optionally, the method further comprises: and the gain selection channel is used for determining the first high-precision operational amplifier module and the second high-precision operational amplifier module to attenuate or gain amplify the measured voltage signal and the standard voltage signal according to the range of the data acquisition module.
Specifically, referring to fig. 1, the specific working steps of the dual-channel voltage signal source ultra-low error high-precision measurement system provided by the application are as follows:
step 1: the clock management module can divide the frequency of the external clock signal according to the measurement requirement and provide synchronous sampling signals for the channel switching module and the data acquisition module, the function of the clock management module is to coordinate the working time sequence of the whole measurement system, the external clock source is an external clock input interface and is used for inputting an external 10MHz clock signal, and the clock selection channel is used for selecting whether the clock source of the synchronous sampling signal output to the data acquisition module is an external clock source or an internal clock source;
step 2: the method comprises the steps of accessing a tested voltage signal source and a standard voltage signal source, passing through a TVS and a surge protection module, and then sending the tested voltage signal source and the standard voltage signal source into an analog switch part, wherein the TVS and the surge protection module are used for protecting electrostatic breakdown and the safety and stability of a later-stage device;
step 3: the main function of the channel switching module is to realize the mutual switching of two channel input signals of the data acquisition board according to the requirement, and the switching is controlled by the synchronous sampling signal provided by the clock management module;
step 4: the signals after the analog switch is switched can have the impedance matching function through the first precise buffer, the second precise buffer, the third precise buffer and the fourth precise buffer, so that the influence of the measuring system on the measured voltage signals is reduced;
step 5: the signals after the analog switch is switched and buffered are sent to the first high-precision operational amplifier module and the second high-precision operational amplifier module to form differential mode amplification, and the signals can be attenuated or amplified through the gain selection channel, so that the signals are converted into the range of the data acquisition module (digitizer);
step 6: then the signal is sent into a first filter and a second filter, and the signal is filtered;
step 7: outputting the filtered signals to a data acquisition module (a digitizer mentioned later is the data acquisition module in the application) through an analog output interface, and converting the filtered signals into digital signals by the digitizer;
step 8: finally, the digital signal can be further transmitted to the computing equipment through GBIP, and software on the computing equipment can complete data processing tasks such as proportion and angle difference calculation of the input signal.
The specific strategy of the channel switching module is as follows:
when the analog switch is used, when the control end is heightened in level, the switch is turned on; when the control end is powered on to a low level, the switch is turned off, the external control of the digitizer triggers the acquisition to start for a high level, the acquisition is stopped after the acquisition setting time, a square wave pulse signal can be used as a switching control signal of the analog switch, a rising positive signal of the square wave is used as a switch in-situ signal and an acquisition starting signal of the digitizer, a falling negative signal of the square wave is used as a switching signal of the switch, the acquisition time of the data acquisition module (the digitizer) is set through application software, and the acquisition is completed before the switch is switched.
The channel switching strategy comprises the following specific processes:
see fig. 2. T in the figure 1 The moment is the switch home position moment of the switching device, and the channel A and the channel B respectively measure U A And U B The rising edge square wave controls the data acquisition module (digitizer) to begin acquiring data. T (T) 2 At moment, the falling edge square wave controls the analog switch to switch two channel signals, and at the moment, the channel A and the channel B respectively measure U B And U A The data acquisition module (digitizer) continues to acquire data. At T 3 The data acquisition module (digitizer) stops acquiring data before the time switch is switched, and the data are stored. T (T) 3 The time switch returns to the original position and the data acquisition module (digitizer) triggers the start of a new data cycle.
If two 50Hz sinusoidal voltages uA (t) and uB (t) are sampled at a sampling rate of 500kHz, the two-channel switching is set to acquire 20 periodic signals at a time, i.e. the sampling duration of both input signals uA (t) and uB (t) is 10 cycles, the frequency of the switching should theoretically be 2.5Hz. According to the technical parameters of the data acquisition module (digitizer), the clock output signal is 10MHz, and when the clock source is subjected to hardware frequency division, only 1/2n frequency division can be actually realized, and the closest frequency after frequency division is 2.3842Hz.
The basic principle is as follows: for standard voltage signal U by two channels A (ain+/Ain-) and the measured voltage signal U B And (Bin+/Bin-) is directly sampled, then error checking is carried out by calculating the ratio of the effective values of the two, and the phase deviation of the signal is measured to obtain the angle difference of the transformer. Each channel in the system is designed with a processing unit of analog signals, after buffering, filtering and amplifying, AD sampling is carried out, and the rated gain of the process of forming digital quantity from input to sampling of two channels is set as G respectively A And G B Gain errors are f respectively A And f B If the input signal is U A And U B Wherein U is A For the standard transformer signal, then there are:
U AQ :U A G A (1+f A )
U BQ ＝U B G B (1+f B ) (1)
wherein U is AQ And U BQ The voltage values including the errors obtained by the final measurement are respectively. According to the definition of the transformer error, the transformer ratio difference f measured by the measuring equipment is:
wherein N is U B And U A Rated ratio f of 0 Is U (U) B Is a practical ratio of (c) to (d). Nominal gain G for two channels A And G B If they are equal, the formula (2) is simplified into:
f≈(1+f 0 )(1+f B -f A )-1
＝f 0 +(1+f 0 )(f B -f A ) (3)
it can be found from the equation (3) that if the channel error f A And f B The measured value f is the same as the true value f 0 Equal. In practice, however, the errors of the two channels tend to be inconsistent. The deviation Δf of the measured values compared to the true error is:
Δf＝f-f 0 ＝(1+f 0 )(f B -f A )≈f B -f A (4)
i.e. the measurement deviation is the difference of the gain errors of the two channels.
The phase deviation generated when the two channels measure the same signal is directly added to the measured value of the angular difference of the measured signal. If the same voltage signal is measured, the ratio difference of the voltage proportion is +/-30 ppm, and the angular difference is +/-5 mu rad; these two errors are the difference between the fixed gain errors of the channels and the phase difference between the channels, which are additionally calculated into the error measurement of the transformer. In order to eliminate the inconsistency of the gains of two measurement channels of a digitizer module to a certain extent and improve the accuracy of proportional measurement, the method and the device for measuring the double channels provided herein perform high-speed alternate switching on channel signals before data acquisition, and eliminate the influence of channel gain errors through calculation.
As shown in the block diagram of fig. 3, if the input signals of the channel a of the channel switching section are U respectively Ain+ And U Ain- The two-end signals of the differential signal input are standard signals. The input signals at the high end and the low end of the channel B are U respectively Bin+ And U Bin- The single-ended voltages measured by two channels of the data acquisition module (digitizer) are U respectively A And U B . Let the corresponding errors of the buffers 1-4 in the system be f B1 ～f B4 The actual amplification factors of the differential mode amplifier are G respectively through the high-precision operational amplifier unit DA And G DB The measurement errors of the two channels of the digitizer are f respectively CHA And f CHB 。
Equations (5), (6) can be obtained when the channel change-over switch S is in the solid line position shown in fig. 3.
U A ＝[U Ain+ (1+f B1 )-U Ain -(1+f B2 )]G DA (1+f CHA ) (5)
U B ＝[U Bin+ (1+f B3 )-U Bin- (1+f B4 )]G DB (1+f CHB ) (6)
Let the intrinsic phase deviation between two channels (including the channel buffer circuit, shaping circuit and measuring channel of data acquisition module (digitizer)) be
The actual angle difference between the input signals is +.>
U measured by data acquisition module (digitizer) A And U B Angle difference of->
Will be the sum of the two, namely:
in the circuitDuring design and component selection, the buffer can be manually selected to have similar error characteristics, namely f B1 ≈f B2 ≈f BA . It is also possible to make 3 and 4 satisfy f B3 ≈f B4 ≈f BB . The voltage ratio K of the two channels 1 The method comprises the following steps:
similarly, when the channel switch is in the dashed line position in FIG. 3,
at this time, the input signals are exchanged by the channel switching module, and the signal angle difference between the A channel signal and the B channel signal becomes
The inherent angle deviation of the acquisition channel at the rear end of the change-over switch is unchanged, so that the measured signal angle difference +.>
The method comprises the following steps:
synthesizing the formula (8) and the formula (9) according to the formula (11) to obtain a synthesis ratio, namely a ratio difference K:
synthesizing the formula (7) and the formula (10) to obtain:
as can be seen from the formula (11), in the synthesized proportional calculation formula, errors of the buffer, the operational amplifier and the data acquisition module (digitizer) channel cancel each other out, the synthesized proportion is equal to the ratio of the differential pressure of the input channel B to the input voltage of the input channel a, and errors of each element in the system do not affect the final synthesized proportion K. As can be derived from equation (12), the inherent angular offset between the acquisition channels of the data acquisition module (digitizer) has been eliminated by two measurements.
Then, according to the error definition of the transformer, when the measured voltage signal source is a voltage transformer, calculating the ratio difference f and the angle difference delta of the measured transformer as follows:
the expression (13) represents an ideal derivation that considers the errors of the buffers, op-amps and channels of the data acquisition module (digitizer) in the system to remain unchanged before and after the switching action, so that the errors they introduce can be completely cancelled out by synthesis. However, in practical applications, the above-mentioned components are not possible to meet this requirement, so that the measured synthesis ratio still has a residual error introduced by the stability of each component, but its value has been greatly reduced with respect to the error introduced by the accuracy of the components before synthesis.
Further, fig. 4 shows a schematic diagram of the measured voltage signal source and the standard voltage signal source waveforms; FIG. 5 shows a schematic waveform diagram at channel switching; fig. 6 shows a schematic diagram of the buffered, gain 0.5, filtered waveform after channel switching.
Therefore, the ultra-low error high-precision measurement system of the dual-channel voltage signal source solves the measurement deviation caused by inconsistent dual-channel gain of the module and improves the measurement precision based on errors caused by different channel circuits in the verification measurement of the current voltage signal source (the two errors are the difference value of the fixed gain errors of the channels and the phase difference between the channels, and can be additionally calculated into the error measurement result of the transformer).
And in the broadband verification of the input 3V power frequency signal, the ratio difference of the verification instrument is smaller than 1 multiplied by 10 < -6 >, and the angle difference is smaller than 1 multiplied by 10 < -7 > rad. In conclusion, the measurement method provided by the project has wide engineering application and achievement popularization space.
The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present disclosure unless it is specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but should be considered part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.
Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
In the description of the present disclosure, it should be understood that the azimuth or positional relationships indicated by the azimuth terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal", and "top, bottom", etc., are generally based on the azimuth or positional relationships shown in the drawings, merely to facilitate description of the present disclosure and to simplify the description, and these azimuth terms do not indicate and imply that the apparatus or elements referred to must have a specific azimuth or be configured and operated in a specific azimuth, and thus should not be construed as limiting the scope of protection of the present disclosure; the orientation word "inner and outer" refers to inner and outer relative to the contour of the respective component itself.
The foregoing is merely a preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (6)
1. The utility model provides a binary channels voltage signal source ultralow error high accuracy measurement system which characterized in that includes:
the channel switching module is composed of high-speed precise analog switches and is used for realizing the mutual switching of the differential signals of the tested voltage signals and the standard voltage signals of the two channels of the data acquisition module according to the preset switching frequency;
the first precision buffer, the second precision buffer, the third precision buffer and the fourth precision buffer are used for realizing impedance matching of the measured voltage signal or the differential signal of the standard voltage signal, and reducing the influence of the dual-channel error precision measurement system on the measured voltage signal;
the first high-precision operational amplifier module and the second high-precision operational amplifier module are used for carrying out differential mode amplification on the measured voltage signal or the standard voltage signal and converting the measured voltage signal into the range of the data acquisition module;
the first filter and the second filter are used for filtering the tested voltage signal or the standard voltage signal and outputting the filtered voltage signal or the standard voltage signal to the data acquisition module through an analog output interface;
the data acquisition module of the digitizer converts the received standard voltage signals and the detected voltage signals into detected voltage digital signals and standard voltage digital signals;
and the computing equipment is used for performing error computation according to the measured voltage digital signal and the standard voltage digital signal.
2. The system of claim 1, further comprising: the first TVS and the surge protection module and the second TVS and the surge protection module are used for sending the measured voltage signal and the differential signal of the standard voltage signal to the channel switching module so as to prevent the electrostatic breakdown of the rear-stage device.
3. The system of claim 1, further comprising: and the external clock input interface is used for connecting an external clock source.
4. A system according to claim 3, further comprising: and the clock selection channel is used for selecting whether the clock source of the synchronous sampling signal output to the data acquisition module is an external clock source or an internal clock source.
5. The system of claim 4, further comprising: and the clock management module is used for dividing the frequency of the external clock source, providing synchronous sampling signals for the channel switching module and the data acquisition module, and coordinating the working time sequence of the dual-channel error precision measurement system.
6. The system of claim 1, further comprising: and the gain selection channel is used for determining the first high-precision operational amplifier module and the second high-precision operational amplifier module to attenuate or gain amplify the measured voltage signal and the standard voltage signal according to the range of the data acquisition module.
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