JPH0438600Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention measures the amplitude error and phase angle error of a digital transformation device that samples an analog input signal using a predetermined sampling pulse, converts it into a digital signal, and outputs it. This invention relates to an error testing device.

[Conventional technology]

Conventionally, as a device for measuring the amplitude error and phase angle error of a digital transformation device that samples an analog input signal, converts it into a digital signal, and outputs it, there is, for example, an error testing device described in JP-A-57-67327. , this conventional device is constructed as shown in FIG.

In the figure, 1 is an AC power supply, 2 is a line connected to the power supply 1, and 3 is a digital transformation device as a device under test. An analog input signal from a power supply 1 input via a line 2 is sampled and converted into a digital signal. 4
is an error testing device.

This conventional error testing device 4 is formed by the following circuits () to (), although not shown.

() A sampling pulse generation circuit that generates sampling pulses synchronized with the analog input signal of line 2.

() An A/D converter that converts an analog input signal into a reference digital signal using a sampling pulse.

() The sampling pulse is supplied to the transformer 3 via the line 5, and the sampling pulse is supplied to the transformer 3 via the line 6.
An interface circuit that takes in the digital signal to be detected from.

() Obtain the analog signal waveforms of the reference digital signal and the digital signal to be detected using Fourier series expansion formulas, and calculate the amplitude and phase of the analog signal waveforms reconstructed based on both digital signals from the coefficients of both expansion formulas. a calculation unit that detects the difference and calculates the amplitude error and phase angle error of the transformation device 3 from the difference.

() A display unit consisting of a printer, etc. that displays the amplitude error and phase angle error calculated by the calculation unit.

Then, the analog input signal of the power supply 1 input to the transformer 3 via the line 2 is taken into the A/D converter of the transformer 3.

This converter is connected to the error testing device 4 via the line 5.
A sampling pulse is supplied from the sampling pulse generation circuit of , the analog input signal is sampled according to this pulse, and the digital signal formed by this sampling is sent to the error testing device via the line 6 as a digital signal on the measurement side. It is sent to the calculation section No. 4.

At this time, in the error testing device 4, the line 2
The analog input signal is input to the built-in A/D conversion section, and this conversion section samples the analog input signal according to the sampling pulse of the sampling pulse generation circuit. The signal is sent to the calculation unit as a signal.

Then, this calculation section obtains an analog signal waveform reconstructed from each of the two digital signals, for example, by expanding a Fourier series based on each of the two digital signals for one period of the analog input signal.

Furthermore, the amplitude and phase of both analog signal waveforms are determined by the cos coefficient and sine coefficient in the expansion equation at this time, and from the difference, the amplitude and phase of the transformer 3 are determined based on the amplitude and phase based on the reference digital signal. Measure the error.

[The problem that the idea aims to solve]

In the case of the conventional error testing apparatus 4 shown in FIG. A sampling pulse is supplied to the metamorphic device 3, and a part of the metamorphic device 3,
In other words, in order to operate the A/D converter and convert it into a digital signal, amplitude errors and phase angle errors occur when the entire transformer 3 is actually operating with its own sampling pulse, that is, in the actual operating state of the transformer 3. Therefore, there is a problem in that it is not possible to make a comprehensive determination of errors in the metamorphic device 3 as a whole from the measurement results.

Furthermore, as is clear from the description in the above-mentioned publication, the calculation unit of the error testing device 4 expands the Fourier series assuming that the sampling interval and phase of the analog input signal are held constant, so the frequency of the analog input signal is If the sampling pulse of the error testing device 4 becomes out of synchronization with the analog input signal due to fluctuations or the like, it becomes impossible to measure the amplitude error and phase angle error of the transformation device 3.

Therefore, in order to reliably synchronize the sampling pulse with the analog input signal, the error testing device 4
As the sampling pulse generating section, it is necessary to include a pulse generating circuit of a complicated configuration whose frequency and phase change in accordance with an analog input signal such as a PLL system, and there is also the problem that the error testing device 4 becomes complicated and expensive.

The present invention uses the sampling pulse of the digital transformation device to sample the analog input signal and convert it into a digital signal in the test equipment and transformation device regardless of whether this pulse is synchronized with the analog input signal and converts it into a digital signal. It is an object of the present invention to provide an error testing device that measures the amplitude error and phase angle error of a transformer in an actual operating state using an inexpensive configuration.

[Means to solve the problem]

In order to achieve the above object, the error testing device of the present invention includes an interface circuit into which sampling pulses and digital signals from a digital transformation device are input, and an interface circuit that receives analog input signals by using sampling pulses passed through this circuit. An A/D converter that samples and converts it from analog to digital to output a digital signal, a frequency detector that detects the frequency of the analog input signal and outputs a detection signal, and a digital signal from the transformation device via an interface circuit. The digital signal from the converter and the frequency detection signal are input, and an analog signal waveform based on each of the two digital signals is derived using the Fourier series expansion formula, and the amplitude error and phase angle error of the derived analog signal waveforms are calculated. It includes an arithmetic unit that performs calculations, and a display unit that displays the calculated amplitude error and phase angle error.

[Effect]

In the case of the error testing device of the present invention configured as described above, the error testing device and the transformation device each sample an analog input signal and convert it into a digital signal using the sampling pulse of the digital transformation device that is the device under test.

Furthermore, the arithmetic unit, which is supplied with both digital signals and the detection signal of the frequency of the analog input signal of the frequency detection unit, grasps the zero point (zero cross point) and period from the detection frequency of the analog input signal,
Regardless of whether the sampling pulse is synchronized with the analog input signal, the sampling interval and phase of the analog input signal are determined, and a Fourier series is developed based on each of both digital signals.

Then, by this expansion, analog signal waveforms based on both digital signals are reconstructed, amplitude errors and phase errors of the transformer are calculated, and the results are displayed on the display section.

Therefore, the amplitude error and the phase angle error are determined in an actual operating state in which the transformer samples an analog input signal using the sampling pulse of the transformer and outputs a digital signal, and it is possible to comprehensively determine the error of the transformer as a whole.

Moreover, based on the detected frequency of the frequency detection section,
Even if the sampling pulse is not synchronized with the analog input signal, the amplitude error and phase error can be determined by deriving the analog signal waveform from the expansion of the Fourier series, and there is no need to accurately synchronize the sampling pulse with the analog input signal.

Since the sampling pulse of the transformation device is used, there is no need to provide a sampling pulse generator in the error testing device, making the error testing device simple and inexpensive.

〔Example〕

One embodiment will be described with reference to FIG. 2 and the following drawings.

In FIG. 2, 7 is an AC power supply, 8 is a distribution line of the power supply 7, and 11 is a digital transformation device as a device under test, which is equipped with an A/D conversion section 9 having a sampling pulse generation section and an output section 10. There is.

The sampling pulse generation section of the A/D conversion section 9 is composed of a stable constant frequency oscillator using a crystal resonator, etc.
When the frequency is 0Hz, a sampling pulse of 720Hz without fluctuation (fluctuation) and a pulse number that is an integral multiple of the sampling pulse are generated.

In addition, the A/D converter 9 receives a sampling pulse from the generator, and the power supply 7 is inputted via the line 8.
Converts analog input signals from to digital signals.

Further, the output section 10 outputs the pulses and digital signals of the integral multiple of the number of pulses from the A/D conversion section 9 to the lines 12 and 13 as sampling pulses on the reference side and digital signals on the measurement side.

Reference numeral 19 denotes an error testing device, which includes an interface circuit 14, an A/D converter 15, and a frequency detector 1.
6, a calculation section 17 and a display section 18 such as a printer, and is substantially the same as the conventional device 4 shown in FIG. 1 by omitting the sampling pulse generation section and adding a frequency detection section 16.

The interface circuit 14 is connected to the output section 1.
The sampling pulse on the reference side from 0 and the digital signal on the measurement side are taken in.

Further, the A/D converter 15 converts the analog input signal of the power supply 7 inputted via the line 8 into a digital signal using the sampling pulse on the reference side via the interface circuit 14, and forms a digital signal on the reference side. do.

Further, the frequency detection section 16 detects the frequency of the analog input signal and outputs a signal of the detected frequency.

The calculation unit 17 receives the detection signal of the frequency detection unit 16, the measurement side digital signal, and the reference digital signal as input, and generates an analog signal waveform based on each of the two digital signals based on the expansion of the Fourier series, which will be described later. Deriving a waveform and a standard waveform, calculating the amplitude error and phase angle error of both derived waveforms, and calculating the amplitude error and phase angle error of the transformation device 11 based on the amplitude and phase of the waveform based on the reference digital signal. The calculation result is displayed on the display section 18.
Output and display.

Note that the reason why the sampling pulse on the reference side is made an integral multiple of the original sampling pulse is because of the A/D.
This is to improve the conversion accuracy of the converter 15 and increase the reliability of the reference digital signal.

Incidentally, since the sampling pulse generating section of the A/D converter 9 generates sampling pulses and the like regardless of the analog input signal, the sampling pulses and the like are often not synchronized with the analog input signal.

Next, the processing of the arithmetic unit 17 in the case of not being synchronized will be explained.

First, the waveform under test _x is reconstructed from the measurement digital signal and the reference digital signal.
(t) and the standard waveform _s (t) have the waveforms shown in FIGS. 3a and 3b, respectively.

In the figure, D ₁ , ..., D _n are the digital signal strings on the measuring side, d ₁ , ..., _do are the reference digital signal strings, α, β, γ, δ are the waveforms _x (t), _s (t)
The zero points of , τ and τ' are the sampling intervals.

Then, based on the button operation to start measurement, the calculation unit 17 takes in both digital signals, detects zero points α, β, and γ, δ from the inversion change of each signal polarity, and calculates the value of β from D ₂ immediately after zero point α. Determine the digital signal on the measurement side up to the previous D _n-1 as a signal corresponding to one cycle of the analog input signal,
The digital signal on the reference side from d ₂ immediately after the zero point γ to d _{o -1} immediately before δ is also determined as a signal corresponding to one period of the analog input signal.

At this time, based on the difference in sampling frequency, the number of signals for one period (sampling number) D ₂ ~
D _n-1 and d ₂ to d _o-1 are different.

Further, the calculation section 17 takes in both digital signals and also takes in the detection signal of the frequency detection section 16, and determines the frequency of the analog input signal from this signal.

Assuming this frequency, the calculation unit 17 calculates one period T of the analog input signal by calculating T=1/.
, and apply this to the zero points α~β,γ~ in Figure 3 a and b.
Let it be one period of δ.

On the other hand, the expansion formula of the Fourier series of the waveforms _x (t) and _s (t) is shown by the following.

_x (t) = a _xp /2+ _∞ 〓 ⁿ⁼¹ (a _xo cosnt + b _xo sinnt) = a _xp /2+ _∞ 〓 ⁿ⁼¹ c _xo sin (nt + ψ _xo ) ... _s (t) = a _sp /2+ _∞ 〓 ⁿ⁼¹ (a _so cosnt + b _so sinnt) = a _sp /2+ _∞ 〓 ⁿ⁼¹ c _so sin (nt + ψ _so ) ... Note that a _xo and a _so are cos coefficients, b _xo and b _so are sin coefficients,
n is the harmonic order.

Both coefficients can be expressed using the trapezoidal formula as described in the above publication, and for example, the coefficients a _xo and b _xo are expressed as follows.

a _xo = 1/π∫〓 _- 〓 _x (t) cosnt dt …… b _xo = 1/π∫〓 _- 〓 _x (t) sinnt dt …… and the coefficient a _xo , b _xo , a _so , b _so If you find
Based on the coefficients a _xo and b _xo , the amplitude c _xo of waveform _x (t),
The phase ψ _xo is found from c _xo = √ _xo ² + _xo ² ... ψ _xo = t _ao ^-1 a _xo /b _xo ...... Based on the coefficients a _so and b _so as before,
The amplitude c _so and phase ψ _so of the waveform _s (t) are determined.

Furthermore, the obtained amplitudes c _xo , c _so , phases ψ _xo ,
Based on ψ _so , the amplitude error ε _o and phase angle error ψ _o of n harmonics are expressed as ε _o = (c _xo − c _so )/c _so ... ψ _o = ψ _xo − ψ _so ... Therefore, these are the errors of the tested waveform _x (t) with respect to the standard waveform _s (t), that is, the amplitude error and phase error of the transformation device 11.

Each of the coefficients a _xo , b _xo , a _so , and b _so is obtained by the method described below.

That is, in the case of coefficients a _xo and b _xo , as shown in FIG. 3a, the first signal D ₂ of one period T from zero point α
Letting the interval between τo and τo, the following (a) holds true by calculating the trapezoidal formula.

|D ₁ /D ₂ |={(τ−τo)/τo}...(A) From this formula (A), the following formula (B) can be found, and from this formula, the formula (C) for τo can be obtained. is found.

｜D ₁ ｜・τo＝｜D ₂ ｜・(τ−τo)……(A) τo＝｜｜D ₂ ｜/(｜D ₁ ｜+｜D ₂ ｜)}τ
...(C) Also, from the last signal D _n-1 of one period T to the zero point β
Letting the interval up to τ1 be τ1, the following equation (d) for τ1 can be found in the same way.

τ1={|D _n-1 |/(|D _n-1 |+|D _n |)}τ...(d) Furthermore, τ can be found from the following equation (e).

τ = {T - (τo + τ1)} / (m-2) ... (e) Therefore, the calculation unit 17 determines the period T by detecting the frequency, and determines τo and τ1 from the digital signals _D1 , _D2 , _Dn-1 , _Dn , and determines the sampling interval τ from equation (e).

Then, based on this interval τ, the integral formula is expanded by the following trapezoidal calculation (c), and the coefficient is
Find a _xo .

a _xo = (1/π)Σ{τo×D ₂ ×cos nτo×(1/2
)+τ×(D ₂ +D ₃ )×cos n(τo+τ)(1/2)+τ×(D ₃ +D
₄ )×cos n(τo+2τ) (1/2)+……+τ1+D _n-1 ×cos n(τo+
(m-1))τ(1/2)}...(c) The integral formula is also expanded by trapezoidal calculation similar to (c) to find the coefficient b _xo .

Furthermore, in the case of coefficients a _{so and} b _so , (c), (d),
Determine τo', τ1', and τ' in Figure 3b from the same formula as in (e), and determine the coefficients a _so and b _so from the same formula as in (c).

Then, when the coefficients a _xo , b _xo , a _so , b _so are found,
Execute the calculation of the formula ~ to find the errors ε _o and ψ _o .

Note that when determining the errors ε _o and ψ _o for the fundamental wave, n in equation (c) may be set to 1, for example, and in practice, it is sufficient to determine the errors for the fundamental wave.

Next, the processing of the arithmetic unit 17 when the sampling pulse etc. are synchronized with the analog input signal will be explained.

In this case as well, the processing is the same as in the case of no synchronization.

The waveforms _x (t) and _s (t) are shown in Figure 4 a and b.
At this time, the waveform _x
The digital signals D ₂ and D _n-1 of waveform s (t) coincide with the zero points α and δ, and the digital signals d ₂ and d _o-1 of the waveform _s (t) coincide with the zero points γ and δ. τo and τ1 of , and τo′ and τ1′ of b in the same figure are all zero.

Therefore, for example, each coefficient a _xo , b _xo , a _so , b _so is determined by setting τo in equations (e) and (c) to 0, and the errors ε _o and ψ _o are determined from the results.

Even if the sampling pulse is not synchronized with the analog input signal, _the zero _points α,
β, γ, δ and sampling periods τ, τ′ are determined, and the errors ε _o and ψ _o can be determined by expanding each of the measurement-side digital signal and the reference digital signal into a Fourier series.

In this case, the sampling pulse of the transformation device 11 causes the transformation device 11 and the error testing device 19 to convert the analog input signal into a digital signal, and the errors ε _o and ψ _o are obtained by expanding the Fourier series of both signals. Tests can be performed under actual operating conditions.
From this test result, it is possible to determine the error of the entire metamorphic device 11.

Moreover, the test device 19 does not require a sampling pulse generator, making it simple and inexpensive.

Note that the analog input signal from the power source 7 may be either a voltage signal or a current signal.

In addition, in the embodiment, the sampling pulse of the A/D converter 15 is a pulse that is an integral multiple of the sampling pulse of the transformation device 11 in order to obtain the waveform _s (t) with high precision; however, the sampling pulse of the transformation device 11 Of course, the number of pulses may be the same as that of .

[Effect of idea]

Since the present invention is configured as described above, it produces the effects described below.

Using the sampling pulse of the digital transformation device 11, which is the device under test, the error testing device 19 and the transformation device 11 each sample the analog input signal and convert it into a digital signal. The calculation unit 17 to which the frequency detection signal is supplied determines the zero point (zero cross point) and period from the detection frequency of the analog input signal, and determines whether the sampling pulse is synchronized with the analog input signal or not. The sampling interval and phase of the input signal are determined, and a Fourier series is developed based on each of the two digital signals.

Then, by this expansion, the analog signal waveform based on each of the two digital signals is reconstructed, the amplitude error and phase error of the transformer 11 are calculated, and the results are displayed on the display unit. The amplitude error and the phase angle error are determined in an actual operating state in which an analog input signal is sampled with a pulse and a digital signal is output, so that a comprehensive determination of the error of the entire transformer 11 can be made.

Furthermore, even if the sampling pulse is not synchronized with the analog input signal, based on the detection frequency of the frequency detection unit 16, the analog signal waveform is derived from the expansion of the Fourier series and the amplitude error and phase error are found, and the sampling pulse can be converted into an analog input signal. There is no need to precisely synchronize with the input signal.

Since the sampling pulse of the transformation device 11 is used, there is no need to provide a sampling pulse generator in the error testing device 19, making the error testing device 19 simple and inexpensive.

Therefore, it is possible to provide an error testing device that measures amplitude errors and phase angle errors in the actual operating state of the transformer 11 with a simple and inexpensive configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional device, FIG. 2 is a block diagram of an embodiment of the error testing device of this invention, and FIGS. 3 a, b and 4 a, b are explanatory diagrams of the operation of FIG. be. DESCRIPTION OF SYMBOLS 11...Digital transformation device, 14...Interface circuit, 15...Analog-digital conversion section, 16...Frequency detection section, 17...Calculation section, 1
8...Display section, 19...Error test device.

Claims (1)

[Claims for Utility Model Registration] In an error testing device for measuring the amplitude error and phase angle error of a digital transformation device that samples an analog input signal with a sampling pulse of a built-in sampling pulse generator and outputs a digital signal, an interface circuit to which a sampling pulse and a digital signal from the transformation device are input; and an analog circuit that samples the analog input signal and performs analog-to-digital conversion to output a digital signal using the sampling pulse via the interface circuit. a digital conversion section; a frequency detection section that detects the frequency of the analog input signal and outputs an ε detection signal; the digital signal via the interface circuit, the digital signal from the conversion section, and the detection signal are input; an arithmetic unit that derives an analog signal waveform based on each of the two digital signals by an expansion formula of a Fourier series, and calculates an amplitude error and a phase angle error of both the derived analog signal waveforms; An error testing device comprising a display section that displays an error.