CN103969614A - Calibration method for digital multimeter - Google Patents
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- CN103969614A CN103969614A CN201410168978.9A CN201410168978A CN103969614A CN 103969614 A CN103969614 A CN 103969614A CN 201410168978 A CN201410168978 A CN 201410168978A CN 103969614 A CN103969614 A CN 103969614A
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Abstract
The invention discloses a calibration method for a digital multimeter. The measuring range is segmented, a corresponding calibration coefficient is worked out through a measured value and a standard value of a standard workpiece to be measured corresponding to N segmentation points Rn, and a zero offset value, a measured value of an unknown workpiece to be measured is modified through the calibration coefficient, and the applicable range of the calibration coefficient is determined according to the segmentation points Rn. Through the calibration method for the digital multimeter, the precision of the digital multimeter can be improved. Measured values in the region nearby the segmentation points of the applicable range of the calibration coefficient can be modified with the linear spline interpolation method, and the precision is further improved. Besides, the measured values can be processed in advance through average smoothing filtering, and therefore random errors are eliminated.
Description
Technical field
The invention belongs to digital multimeter technical field, more specifically say, relate to a kind of calibration steps of digital multimeter.
Background technology
Digital multimeter is a kind of multifunctional electronic surveying instrument, belongs to electronic measuring technology field.The only guaranteed high precision of surveying instrument itself, provides reliable test data could to instrument user.And digital multimeter can produce some errors that are difficult to avoid in the hardware design of itself, its error main source has:
1. measure the error that chip internal circuit produces;
2. in chip periphery circuit, the precision of resistance is not high enough, and exists certain temperature to float;
3. the noise existing in hardware circuit and interference.
Therefore, if not to the error of digital multimeter inside process just provide it to user use will cause measurement result deviation too large, directly affect the performance of digital multimeter, more can not meet user's measurement demand.How to eliminate error and just become a heavy difficult point in multimeter design.Except hardware circuit is improved, eliminate the effective method of error and exactly multimeter is calibrated.Calibration be electronic measuring instrument from produce to use in one of requisite step.So-called calibration refers under rated condition, for determining surveying instrument instrument or the indicated value of measuring system, or the value of material measure or reference material representative, and one group of relation operates between the corresponding value being reappeared by standard, its objective is by relatively determining the indicating value of measurement mechanism with standard.Measurement data only have through calibration after offer again its accuracy of user's guarantee and reliability.Along with the development of digital multimeter, more and more higher to the requirement of precision, desirability can better improve precision by calibration steps.
Summary of the invention
The object of the invention is to overcome the deficiencies in the prior art, a kind of calibration steps of digital multimeter is provided, improve the precision of digital multimeter.
For achieving the above object, the calibration steps of digital multimeter of the present invention comprises the following steps:
S1: select range, according to the measurement function of selecting, digital multimeter short circuit or open circuit are obtained being partially worth β when leading zero;
S2: remember that current range is R, range is divided into N+1 section, cut-point R is set
n, wherein n represents cut-point sequence number, span is n=1, and 2 ..., N, N represents cut-point quantity;
S3: selective value equals R
nto be measured of standard, to be measured is measured, measured value is designated as x
n, then by the higher digital multimeter of another resolution, to be measured of standard is measured, the measured value obtaining, as standard value, is designated as y
n, calculate calibration factor
S4: to be measured of the unknown is measured, and measured value is designated as x ', adopts calibration factor to calibrate measured value x ', calibration value x
wherein α is the calibration factor adopting, and when measured value, x ' belongs to
calibration factor α=α
1; When measured value, x ' belongs to
calibration factor α=α
n, when measured value, x ' belongs to
calibration factor α=α
n.
Further, when measured value x ' belongs to
time, wherein Δ is the off-set value arranging, and adopts linear spline method to calibrate, the calibration value of measured value x ' is
Further, the Along ent that the cut-point in step S2 is range.
Further, measured value is obtained by the average smooth filtering of measuring actual value, and concrete grammar is: to be measured is measured continuously, obtain K and measure actual value, wherein K >=2, average and obtain measured value K measurement actual value.
The calibration steps of digital multimeter of the present invention, carries out segmentation by range, utilizes N cut-point R
nthe measured value that corresponding standard is to be measured and standard value and zero inclined to one side value calculate corresponding calibration factor, then adopt calibration factor to calibrate the measured value of to be measured of the unknown, thus the precision of raising digital multimeter.For the measured value of calibration factor scope of application cut-point near zone, can further adopt linear spline method to calibrate, further improve precision.The present invention also processes measured value in advance by average smooth filtering, thereby eliminates stochastic error.
Brief description of the drawings
Fig. 1 is a kind of embodiment process flow diagram of the calibration steps of digital multimeter of the present invention;
Fig. 2 is range segmentation schematic diagram in the present embodiment;
Fig. 3 is the error curve diagram of data in table 1;
Fig. 4 is the linear spline interpolation area schematic of the present embodiment;
Fig. 5 is the error curve diagram of data in table 2.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described, so that those skilled in the art understands the present invention better.Requiring particular attention is that, in the following description, in the time that perhaps the detailed description of known function and design can desalinate main contents of the present invention, these are described in here and will be left in the basket.
Embodiment
Fig. 1 is a kind of embodiment process flow diagram of the calibration steps of digital multimeter of the present invention.As shown in Figure 1, the calibration steps of digital multimeter of the present invention comprises the following steps:
S101: select range, according to the measurement function of selecting, digital multimeter short circuit or open circuit are obtained being partially worth β when leading zero.Wherein, zero inclined to one side value method of testing of resistance measurement and voltage measurement is short circuit test pencil, and zero inclined to one side value measurement method of current measurement is to disconnect test pencil.
S102: range segmentation: remember that current range is R, range is divided into N+1 section, cut-point R is set
n, wherein n represents cut-point sequence number, span is n=1, and 2 ..., N, N represents cut-point quantity.
Selecting 400 Ω shelves ranges of resistance is below that example describes.Fig. 2 is range segmentation schematic diagram in the present embodiment.In the present embodiment, range is divided into 4 sections, cut-point can arrange arbitrarily, also can adopt Along ent.In general, cut-point is more, and calibration effect is better, but also can increase algorithm complex.In the present embodiment, adopting 3 Along ents is cut-point, is respectively R
1=100 Ω, R
2=200 Ω and R
3=300 Ω.
S103: obtain calibration factor: selective value equals R
nto be measured of standard, to be measured is measured, measured value is designated as x
n, then by the higher digital multimeter of another resolution, to be measured of standard is measured, the measured value obtaining, as standard value, is designated as y
n, calculate calibration factor
Although to be measured of standard has nominal value, because the reason such as device loss, environmental impact likely produces error, therefore in the present invention with the measured value y of the higher digital multimeter of resolution
nas the standard value of calculating calibration factor use.In calibration process, must adopt than digital multimeter value of settling the standard of at least high one of this digital multimeter resolution, otherwise nonsensical.The resolution of the digital multimeter that the present embodiment adopts is 512, and the resolution of the digital multimeter that measurement standard value adopts so should be at least 612, the accuracy of guarantee standard value like this, and then the accuracy of guarantee calibration factor.The present embodiment Plays value measures by Agilent 34410A612 multimeter.
S104: to be measured of the unknown is measured and calibrated:
To be measured of the unknown is measured, and measured value is designated as x ', adopts calibration factor to calibrate measured value x ', and calibration value is x
wherein α is the calibration factor adopting, and when measured value, x ' belongs to
calibration factor α=α
1; When measured value, x ' belongs to
calibration factor α=α
n, when measured value, x ' belongs to
calibration factor α=α
n.The accommodation that has marked the present embodiment alignment coefficient in Fig. 2, measured value x ' uses calibration factor α between 0～150 Ω
1calibrate, when measured value x ' uses calibration factor α between 150 Ω～250 Ω
2calibrate, when measured value x ' uses calibration factor α between 250 Ω～400 Ω
3calibrate.
The resistance measurement precision of 400 Ω ranges of current 512 multimeters is generally 0.08%～0.1%, if the precision of the U3402A51/2 bit digital multimeter of Agilent is just in 0.08% left and right.And in the present embodiment, adopt can reach ± (0.03%+0.04%) (± (% reading+% range)) of 512 digital multimeter of the present invention, the resistance measurement precision of 400 Ω ranges.Visible, adopt calibration steps of the present invention, can improve the precision of digital multimeter.In the present embodiment, adopt one group of error of measured value, calibration value and standard value before and after calibration whether to meet accuracy requirement to illustrate the effect of calibration steps of the present invention.Table 1 is error contrast before and after calibration steps calibration of the present invention, and unit is ohm.
Table 1
As shown in table 1,40 measurement data, before calibration, have 32 defective, after calibration, only have 5 defective.Fig. 3 is the error curve diagram of data in table 1.As shown in Figure 3, calibration steps of the present invention is better for the calibration effect of systematic error.Be mostly linear error by the error of measuring known digital multimeter, visible the present invention can weaken linear error well, and error is substantially all controlled in permissible error limit.
But from table 1 and Fig. 3, in the present embodiment, near 150 Ω and 250 Ω time, namely, in the time approaching the scope of application cut-point of calibration factor, error becomes greatly gradually, has even exceeded the limits of error.Therefore the present invention also provides a kind of spline method to calibrate near measured value scope of application cut-point, further reduces error, improves precision.
First spline interpolation is carried out to simple an introduction below: spline interpolation is to use a kind of particular section polynomial expression of batten by name to carry out the form of interpolation.Spline interpolation can be used low order polynomial spline to realize less interpolation error.If adopt linear function as interpolating function, be called linear spline interpolation, linear spline interpolation is to couple together the value of approximating function f (x) at x place by interpolation point broken line.
If f (x) is at m+1 node a=x
0< x
1< x
2< ... < x
mfunctional value on=b is f (x
k), (k=0,1,2,3 ... m).Press node [a, b] is divided into n minizone, at each minizone [x
k, x
k+1] on make linear interpolation, obtain the approximate value of f (x)
For the present invention, adopt calibration factor can obtain better calibration effect, therefore only need to adopt linear spline interpolation to the larger region of error, known according to analyzing before, in the present invention, at the scope of application cut-point of calibration factor
the error maximum at place, therefore determines according to scope of application cut-point and the scope of linear spline interpolation belongs at measured value x '
time, wherein Δ is the off-set value arranging, and adopts linear spline method to calibrate, the calibration value of measured value x ' is
in the time adopting linear spline method, the cut-point R in step S102
npreferably adopt range Along ent, so that the calibration result of linear spline method is more accurate.
Fig. 4 is the linear spline interpolation area schematic of the present embodiment.As shown in Figure 4, in the present embodiment, offset value delta=20 Ω is set,, when measured value is positioned at 130 Ω～170 Ω, within the scope of 230 Ω～270 Ω time, adopts respectively the measured value x of 150 Ω, 200 Ω and 300 Ω
n, standard value y
ncarry out linear spline interpolation.Can in the situation that not increasing to be measured measured value of standard, adopt linear spline interpolation to calibrate like this.
Table 2 is to increase linear spline interpolation calibration steps of the present invention is improved to front and back error contrast.Before improvement, only adopt calibration steps of the present invention, the calibration steps after improvement adopts linear spline method to calibrate in linear spline interpolation region.
Table 2
As shown in table 2,40 measurement data, do not adopt the calibration steps of linear spline method have 5 defective, it is all qualified to adopt after linear spline method.Fig. 5 is the error curve diagram of data in table 2.As shown in Figure 5, adopt after linear spline method, near the error scope of application cut-point of calibration factor is obviously dwindled, and precision obviously improves.
Can also evaluate calibration effect by remaining standard deviation sigma herein.Remaining standard deviation sigma can be used for the size of the variation of mean rate of weighing the disposable observation of all enchancement factors to true value, and after the less calibration effect of σ, precision is higher.σ is defined as follows:
Wherein: y
ifor standard value,
for calibration value, M is measurement point number (the present embodiment M=40).
Carry out technology according to the data in table 1 and table 2, the remaining standard deviation that does not adopt the calibration steps of linear spline method is 0.1177, adopt the remaining standard deviation 0.0789 of the calibration steps after linear spline method improves, the remaining standard deviation after visible improvement is less, calibration better effects if.
In digital multimeter, the noise on electronic circuit and extraneous interference all can bring stochastic error, and this error has uncertainty, and being embodied in measurement result is exactly that measurement data is beated at random near certain value.According to stochastic error theory, in the time that metering number of times infinitely increases, the limit of the arithmetic mean of error is zero.On the basis of this theory of errors, for same to be measured, measured value can be obtained by the average smooth filtering of measuring actual value, concrete grammar is: to be measured is measured continuously, obtain K and measure actual value, wherein K >=2, average and obtain measured value K measurement actual value, thereby eliminate stochastic error.In the present embodiment, by average after 5 measurement data summations that obtain continuously, next send to host computer again.Data through average smooth filtering are milder compared with the data before filtering, are more conducive to observe.
Adopt the calibration steps of introducing linear spline method below, and measured value is carried out to weights smothing filtering, measurement effect to 6 of digital multimeter kinds of measurement functions is tested, and measurement function comprises: DC voltage measurement, ac voltage measurement, DC current measurement, ac current measurement, resistance measurement, diode measurement.(1) DC voltage measurement test
Measuring voltage scope: 0-1000V;
Measure gear: 400mV/4V/40V/400V/1000V;
Measuring accuracy: ± (0.04%+0.03%)
Table 3 is vdct tables.
Table 3
(2) ac voltage measurement test
Measuring voltage scope: 0-1000V;
Measure gear: 400mV/4V/40V/1000V;
Measuring accuracy: ± (0.4%+0.3%) 400mV/4V/40V/1000V
Table 4 is alternating voltage test charts.
Table 4
(3) DC current measurement test
Measurement range: 0-40A;
Can survey gear: 400uA/4000uA/40mA/400mA/40A;
Measuring accuracy: ± (0.2%+0.15%)
Table 5 is DC current test charts.
Table 5
(4) ac current measurement test
Measurement range: 0-10A;
Can survey gear: 400uA/4000uA/40mA/400mA/10A;
Measuring accuracy: ± (0.7%+0.5%)
Table 6 is alternating current test charts.
Table 6
(5) resistance measurement test
Measurement range: 0 Europe-40M Europe;
Measure gear: 400 Ω/4k Ω/40k Ω/400k Ω/4M Ω/40M Ω;
Measuring accuracy: ± (0.03%+0.04%) (range <4M Ω)
± (0.3%+0.4%) (range >=4M Ω)
Table 7 is resistance test tables.
Table 7
(6) diode measurement test
Measurement range: 0-1.5V;
Precision: ± (0.5%+2%)
Table 8 is Test Diode tables.
Table 8
Can find out according to the measurement effect of above 6 kinds of measurement functions, adopt digital multimeter of the present invention on various measurement functions, all to there is preferably precision.
Although above the illustrative embodiment of the present invention is described; so that those skilled in the art understand the present invention; but should be clear; the invention is not restricted to the scope of embodiment; to those skilled in the art; as long as various variations appended claim limit and definite the spirit and scope of the present invention in, these variations are apparent, all utilize innovation and creation that the present invention conceives all at the row of protection.
Claims (4)
1. a calibration steps for digital multimeter, is characterized in that, comprises the following steps:
S1: select range, according to the measurement function of selecting, digital multimeter short circuit or open circuit are obtained being partially worth β when leading zero;
S2: remember that current range is R, range is divided into N+1 section, cut-point R is set
n, wherein n represents cut-point sequence number, span is n=1, and 2 ..., N;
S3: selective value equals R
nto be measured of standard, to be measured is measured, measured value is designated as x
n, then by the higher digital multimeter of another resolution, to be measured of standard is measured, the measured value obtaining, as standard value, is designated as y
n, calculate calibration factor
S4: to be measured of the unknown is measured, and measured value is designated as x ', adopts calibration factor to calibrate measured value x ', calibration value x
wherein α is the calibration factor adopting, and when measured value, x ' belongs to
calibration factor α=α
1; When measured value, x ' belongs to
calibration factor α=α
n, when measured value, x ' belongs to
calibration factor α=α
n.
2. calibration steps according to claim 1, is characterized in that, in described step S4, when measured value, x ' belongs to
time, wherein Δ is the off-set value arranging, and adopts linear spline method to calibrate, the calibration value of measured value x ' is
3. calibration steps according to claim 2, is characterized in that, the Along ent that the cut-point in described step S2 is range.
4. according to the arbitrary described calibration steps of claims 1 to 3, it is characterized in that, described measured value is obtained by the average smooth filtering of measuring actual value, concrete grammar is: to be measured is measured continuously, obtain K and measure actual value, wherein K >=2, average and obtain measured value K measurement actual value.
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| CN113156357A (en) * | 2020-12-31 | 2021-07-23 | 杭州拓深科技有限公司 | Segmented current transformer correction method and device, electronic device and storage medium |
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