JPH05215797A - Automatically measuring apparatus for non-linear distortion - Google Patents

Abstract

PURPOSE: To automatically, rapidly and accurately measure non-linear strain by using two first and second frequency analyzers connected in siries. CONSTITUTION: This measuring constitution has first and second frequency analyzers 1, 2 connected in series. The analyzer 1 discriminates the max. frequency component f1 from the measuring signal from the output terminal 3 of an object 4 to be measured to measure the frequency thereof. The analyzer 1 further separates the frequency component f1 to form a residual signal containing no component f1. This residual signal is supplied to the analyzer 2. The analyzer 3 discriminates the second frequency component f2 of the max. amplitude from the residual signal to measure the frequency thereof to subject the same to next processing at an output terminal 6. At the same time, a second residual signal containing no frequency component f2 is formed to be outputted from an output terminal 7 to be subjected to subsequent evaluation. By this constitution, the full automatic measurement of the non-linear strain of the object to be measured is performed by a difference sound method or a mutual modulation method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, as described in the preamble of claim 1, uses an intermodulation method or an intermodulation method (Intermod method).
operations-oder Differentzto
The present invention relates to a device for automatically measuring non-linear strain of a measurement object by n-Verfahren).

[0002]

2. Description of the Related Art Nonlinear distortion in electroacoustics is measured by the German Industrial Standard DIN 45403 for the difference sound method.
Is defined by the third leaf of the above, and the intermodulation method is defined by the fourth leaf of the same. In the case of the difference tone method, the frequencies f1 and f
Two signals of the same amplitude with 2 and a specified frequency interval are fed to the input of the object to be measured, and the asymmetrical distortion of the object to be measured causes a difference tone from zero frequency to an integer multiple of the frequency interval. According to the DIN standard, how to measure the difference sound content of even-order or odd-order is accurately defined. In the case of the intermodulation method, the low frequency f1
A signal having a large amplitude at and a signal having a small amplitude at a high frequency f2 are supplied to the input end of the measurement object. In addition to the original signal, additional modulation frequencies occur at the output of the object to be measured, and these frequencies and amplitudes are measured. Individual sideband frequency (Seitenfrequency)
From the measured RMS value of the measured signal of the higher frequency to DIN
Intermodulation rate according to the standard
ionsfactor) is calculated. The measurement of the frequency components necessary for performing the difference tone method or the intermodulation method has heretofore mostly been performed by analog measurement techniques. It uses a heterodyne analyzer, which measures the frequency and amplitude of all components of the frequency spectrum,
The difference sound content rate or the intermodulation rate is calculated from the thus-measured effective value. It is known to carry out these methods with digital measurement techniques, for example by calculating the full spectrum with a fast Fourier transform (FFT). However, all known analog or digital measuring methods always require that a predetermined measuring sequence be followed, which requires a long measuring time. In other words, the automatic measurement and identification of the frequency positions of the individual frequency components can only be performed with known methods with a long measuring time. SMPTE
Or CCIF multiple tone method (CCIF-Mehrton
A configuration for the selective measurement of the intermodulation rate of the object by means of a method is already known (for example, DE-PS).
3114008 or 1981 in the Funkschau magazine.
25-26, page 79-81). In this method, a high-pass filter and a low-pass filter are used for frequency separation, and the measurement with this known arrangement is therefore relatively inaccurate. This is because this filter is roughly the level of disturbance (Storgross).
This is because en) is also measured. Therefore, an object of the present invention is to provide a configuration capable of automatically, more quickly and accurately measuring these measurements by the difference tone method or the intermodulation method. The above-mentioned problem is solved starting from the preamble of claim 1 and by its features. Advantageous details emerge from the subclaims which are adapted to the difference tone method or the intermodulation method, respectively.

[0003]

SUMMARY OF THE INVENTION An automatic non-linear strain measuring apparatus according to the present invention comprises two signals (f1, f1) having different frequencies.
The configuration for automatically measuring the non-linear strain of the measurement target by evaluating the frequency spectrum generated when 2) is supplied to the output end of the measurement target, which is connected in series.
And a second frequency analyzer (1, 2), and the first frequency analyzer (1) is the output end (3) of the measurement object (4).
Of the measurement signal supplied from the measurement signal, the frequency component having the maximum amplitude (for example, f1) is identified, its frequency (f1) is determined, and this frequency component is separated from the measurement signal to form a residual signal. The second frequency analyzer (2) supplies the second frequency analyzer (2) with the frequency component (eg, f2) having the maximum amplitude, and determines the frequency (f2) from the residual signal. However, this frequency f2 component is separated from the residual signal, so that from these two measured frequencies (f1, f2) of the maximum amplitude, the second modulation is performed by the intermodulation method or the two-tone method. A frequency component for measuring the effective value of the measurement signal (7) from the frequency analyzer (2) (for example, frequency component D = f2-f by the difference tone method).
1) to determine the measurement signal (7) for the frequency component
The effective value of is measured.

The arrangement according to the invention enables a fully automatic measurement of the linear distortion of the measuring object by means of the difference tone method or the intermodulation method. This is because the configuration according to the present invention enables the automatic identification of both frequency components supplied to the input end of the measurement object. It is then possible in a known manner to determine the frequency components of the measurement signal whose effective value is to be measured, from which the difference tone content or intermodulation rate according to the DIN standard is calculated. The use of a frequency analyzer ensures a frequency-selective measurement of each frequency component and avoids measurement inaccuracies due to the measurement of anharmonic distortions around the original measurement frequency. Moreover, the arrangement according to the invention can be constructed in analog or digital technology. In analog technology, for example, a normal heterodyne analyzer is used as a frequency analyzer, which makes it possible to determine the frequencies and amplitudes of the desired frequency components f1 and f2, and also to separate these frequency components from the original input signal. It is also possible to create the remaining residual signal without these frequency components. However, it is particularly simple to implement the arrangement according to the invention in digital technology. In this case, the frequency analyzer
Commercially available equipment is suitable. These operate according to known frequency conversion methods, such as FFT. Further, the frequency component having the maximum amplitude can be further identified and separated from the digitized input signal, and the remaining residual signal can be produced as a digital signal without these frequency components and can be used for the subsequent evaluation. In principle, all known frequency conversion methods are suitable for this purpose. For example, H. W. Schus
sler "Digital system for signal processing""D
digital System zur Signa
lverarbeitung ", Spring, Germany
Suitable are those published by er Publishing Company, 1973, in particular as described on pages 165 to 170. The configuration according to the present invention not only enables the fully automatic measurement of the difference sound content rate or the intermodulation rate, but also allows the measurement to be performed in parallel,
It enables much faster measurement than conventional methods.

[0005]

Embodiments of the present invention will be described in more detail with reference to the drawings. FIG. 1 shows a principle circuit diagram according to the invention for the measurement of the difference tone distortion by the difference tone method shown in the third leaf of DIN 45403. This measurement arrangement has first and second frequency analyzers 1 and 2 connected in series,
From the measurement signal supplied by the first frequency analyzer 1 from the output 3 of the object 4 to be measured, the frequency component f1 having the largest amplitude in this measurement signal is identified. In the case of the difference sound method, two frequencies f1 and f2 having the same amplitude are supplied to the input end of the measuring object 4, but the first frequency analyzer 1 outputs one of these two components having the same magnitude. Identify as the maximum value. The illustrated example shows a case where the first frequency f1 is identified as the maximum value. The first frequency analyzer 1 is arranged not only to identify the maximum frequency component, but at the same time to measure its frequency. Therefore, at the output end 5 of the first frequency analyzer 1, the frequency f1 of the maximum amplitude of the measurement signal
A digital signal corresponding to the value of Frequency analyzer 1
From the original measurement signal, this first frequency component f
It is configured to separate 1's and also produce a residual signal that no longer contains this first frequency component f1. This residual signal is then fed to a second frequency analyzer 2, which is constructed similarly to the analyzer 1. The second frequency analyzer 2 further identifies from the residual signal a second frequency component of maximum amplitude therein (f2 in this example), measures its second frequency and at the output 6 the following processing: To serve. At the same time, a second residual signal is produced which no longer contains this frequency component f2, which is output at the output 7 for further evaluation. The first and second frequency values f1 and f2 thus measured
The value of the difference D = f2-f1 is obtained in the adder circuit 8 from the value of. According to the DIN standard, the steps necessary for measuring the second-order difference sound distortion after the second-order difference sound distortion coincides with the effective value of the difference sound f2-f1 are as follows. Adjust to f2-f1 and use this bandpass filter 9
It is only necessary to measure the effective value of this frequency component using the effective value measuring device 10 with respect to the residual signal supplied to. At the output end of the measurement object, in addition to the above, the effective value of all frequency mixing at the output end 3 is measured as the voltage Ua through the effective value measuring device 11, and the frequency components f2-f1 measured by the effective value measuring device 10 are measured. From the rms value of and the rms value Ua, the equation shown in FIG. Thus, the second-order difference sound content rate d2 according to the DIN standard is calculated by a known computer (not shown).

In the same way, for example, the third-order upper and lower differential sound content can also be calculated, for which two tunable bandpass filters 12 and 13 are provided. One band filter 12 frequency is adjusted to 2f1-f2. In the adder 14, the difference between the component of the lower frequency f1 and the component of the difference D of both frequency components f2-f1 is formed. For this purpose, an additional identification circuit is assigned to the outputs 5 and 6 of the frequency analyzer, from which it is determined which of the two frequencies f1 and f2 is respectively greater. However, this confirmation decision is mainly made directly and easily by the frequency analyzers 1 and 2,
As defined, the component of the frequency f1 whose output end 5 is lower,
Further, the main force end 6 supplies the component f2 of the higher frequency.
Similarly, in the adder 15, the sum (2f2-f) between the frequency component f2 having the higher frequency and the difference D (= f2-f1) is obtained.
1) is formed and the bandpass filter 13 is adjusted to this frequency. Therefore, for the determination of the third-order difference sound content rate,
Bandpass filters 12 and 1 automatically adjusted to frequency components
3 filters and outputs the corresponding frequency components from the residual signal at the output 7, and the corresponding RMS values of these frequency components are measured again via the RMS measuring units 16 and 17. And the equation shown in Fig. 1 by its effective value Thus, the third-order upper and lower differential sound content rates considering Ua are
It is calculated through a known computer (not shown).

Although the arrangement according to FIG. 1 has been shown mainly in analog technology, it can equally well be realized in digital technology. Moreover, it is the usual known F
This is possible by using an FT analyzer, which is a function of the frequency analyzers 1 and 2 and a tunable bandpass filter 9, 1.
It replaces the two and thirteen. By digitizing the output signal of the measuring object 4, the formation of the residual signals of the frequency components f1 and f2 and the adjustment of the band-pass filters 9, 12, 13 to the desired frequency components respectively are purely digital frequency conversions. Can be done by Since it can be implemented, for example, by the FFT method, a particularly simple structure is possible. FIG. 2 shows a configuration for automatically measuring the non-linear strain of the measuring object 4 by the intermodulation method. For this purpose, both frequency analyzers 1 and 2 connected in series are also provided for this purpose, which in the case of the intermodulation method are supplied with two signals f1 and f2 of different amplitudes. .. As a result, the component of the lower frequency f1 is automatically identified at the output end 5 of the first frequency analyzer 1, and the component of the higher frequency f2 is identified through the output end 6 of the frequency analyzer 2.
The difference f2-f1 is formed in the adder circuit 8, and the sum f2 + f1 is further formed in the second adder circuit 20.
The addition circuit 8 causes the bandpass filter 21 to change the frequency f2.
Adjusted to -f1. The bandpass filter 22 is adjusted to the sum f2 + f1 by the adder 20. The effective values of these frequency components [f2-f1] and [f2 + f1] are further measured by the effective value measuring devices 23 and 24. From these measured effective values, the second-order intermodulation rate can be calculated, for example, according to the DIN standard. Second for this
The circuit shown in the figure is further provided with another effective value measuring device 25, which measures the effective value of f2. Due to the corresponding formation of the difference and the sum of the frequencies f1 and f2, also intermodulation distortions of the third and higher orders can be measured in this way. For that purpose, only a bandpass filter that can be adjusted according to the third-order frequency component is required.
This configuration according to FIG. 2 can also be implemented in analog or purely digital technology.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment for measurement by a difference tone method.

FIG. 2 is a circuit diagram of a second embodiment for measurement by the intermodulation method.

[Explanation of symbols]

1, 2 Frequency analyzer 3, 5, 6, 7 Output terminal 4 Measurement object 8, 14, 15, 20 Addition circuit 10, 11, 16, 17, 23, 24, 25 Effective value measuring device 9, 12, 13 , 21, 22 bandpass filters

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Bolfgang Kufueru Federal Republic of Germany Day-8260 Miurdorf Patz Southtraße 22 (72) Inventor Bolfgang Colognehien Germany Day-8029 Sauerlaha Yazbergbek 4

Claims (4)

[Claims] 1. Two signals of different frequencies (f1, f)
2) is a configuration for automatically measuring the non-linear strain of the measurement object by evaluating the frequency spectrum generated when supplying 2) to the output end of the measurement object. Frequency analyzer (1,
2), the first frequency analyzer (1) identifies the highest amplitude frequency component (eg f1) of the measurement signal supplied from the output (3) of the object (4) to be measured. , Its frequency (f
1) is determined, and this frequency component is separated from the measurement signal to form a residual signal, which is supplied to the second frequency analyzer (2), which second frequency analyzer (2) It identifies the frequency component of maximum amplitude (eg f2) from this residual signal, determines its frequency (f2) and separates this frequency f2 component from the residual signal, whereby these measurements of maximum amplitude are taken. From the two frequencies (f1 and f2), the component of the frequency (for example, the difference tone) for measuring the effective value of the measurement signal (7) from the second frequency analyzer (2) by the principle of the intermodulation method or the two-tone method. Frequency component D = f2-f1) according to the method, and the effective value of the measurement signal (7) is measured for the frequency component. 2. The structure according to claim 1, wherein the second-order difference sound content is measured according to the difference sound method by supplying two signals f1 and f2 having different frequencies but the same amplitude. A means (for example, bandpass filter 9 and effective value measuring device 10) for measuring an effective value of the residual signal (7) output from the second frequency analyzer (2) at the frequencies f2-f1. The non-linear strain automatic measuring device according to claim 1, which is characterized. 3. The configuration according to claim 1, for measuring the third-order difference sound content according to the difference sound method by supplying two signals f1 and f2 having different frequencies but the same amplitude. And a means for measuring an effective value of the residual signal (7) output from the second frequency analyzer (2) at both frequency 2 · f2-f1 and frequency 2 · f2 + f1. The automatic measuring device for nonlinear strain according to claim 1. 4. A first signal having a lower frequency f1 and a larger amplitude, and a second signal having a higher frequency f2 and a smaller amplitude are supplied to an input end of an object to be measured (4). However, the residual signal (7) output from the second frequency analyzer (2) has a configuration for measuring second-order intermodulation distortion by the intermodulation method even at frequencies f2-f1. Frequency f
Means (21, 23, 2 for measuring effective value even with 2 + f1
2, 24). The automatic non-linear strain measuring device according to claim 1, further comprising: