JPS637954Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a wow and flutter measuring device for measuring rotational unevenness of various rotating bodies such as tape recorders and record players. The present invention relates to a wow and flutter measuring device capable of measuring rotational unevenness.

[Background technology and its problems]

These days, motors, engines, and the like are used as power sources for everything. In the case of devices that drive devices by rotating shafts in this way, the rotational accuracy of the drive shafts of the motors and engines mentioned above, as well as slight eccentricity, play, friction, unbalance, etc. of each rotating part, etc. This adversely affects the rotational drive of the rotating body, causing periodic rotational unevenness, that is, wow and flutter. In particular, in tape recorders, record players, etc., the wow and flutter of rotating bodies such as tape reels and turntables directly affect the playback sound.
This resulted in deterioration of sound quality and significantly reduced the performance of the device.

For this reason, in the above-mentioned tape recorders and record players, it has been necessary to measure the wow and flutter of rotating bodies such as tape reels to understand the performance of the device and use it as data for quality control, product development, etc.

Therefore, a wow and flutter measuring device has been devised and widely used to measure the wow and flutter of this type of rotating body.

The configuration of the conventional wow and flutter measuring device described above is as follows:
For example, a case will be explained in which the rotation unevenness of a tape reel of a tape recorder is measured. by the way,
When measuring the rotational unevenness of the tape reel of the tape recorder mentioned above, a 3KHz pure tone recorded with a tape recorder with extremely low wow and flutter is played back on the tape recorder under test, and fluctuations in the frequency of this playback signal are detected. This method is used.

The 3KHz pure tone reproduced by this tape recorder under test is input as an input signal from the input terminal of the wow/flatter measuring device, and first, amplitude changes are suppressed by an amplitude limiter. Next, the output signal from the amplitude limiter is converted from a frequency change to a voltage change by a frequency-to-voltage converter, and is led to a display meter through an auditory correction filter, so that the wow and flutter value is displayed as an effective value. is being done.

By the way, the above-mentioned wow and flutter measuring device can only measure signals of a specific frequency, and its uses are limited. That is, uneven rotation of the turntable of a record player, uneven rotation of a servo motor, etc. cannot be measured by the test tape playback method as in the above-mentioned tape recorder, and therefore cannot be measured using the same equipment.

For this reason, conventionally, the
A wideband type wow and flutter measurement device is known in which the frequency to be measured, that is, the rotational speed can be arbitrarily set over a wideband. The configuration of such a conventional broadband type wow and flutter measuring device is shown in FIG. This wow and flutter measuring device includes an amplitude limiter 1 that limits the amplitude of the signal under test, a converter 1 that converts frequency changes into voltage changes, and a conversion ratio of output voltage to input signal frequency according to the frequency range of the signal under test. It consists of a frequency-voltage converter 2 capable of switching, a sensitivity corrector 3 for performing sensitivity correction, and a meter 4 for displaying measured values. In the above wow/flatter measuring device,
The capacitor capacity included in the frequency-voltage converter 2 is changed according to the frequency of the signal to be measured, and the ratio of the output voltage to the frequency of the input signal is set to an appropriate value. While looking at the correction meter 5, it is possible to display the wow and flutter as a ratio between the output voltage and the amplitude of the voltage fluctuation using the sensitivity corrector 3 in accordance with the reference voltage.

However, in the conventional wideband wow and flutter measuring device as described above, the signal under test is transmitted to the frequency-voltage converter 2 with a wide band, so noise and interference may occur in the signal under test. This has the disadvantage that when a signal occurs, accurate measurement values cannot be obtained due to this influence.

[Purpose of invention]

Therefore, the present invention was proposed in order to eliminate the drawbacks of the conventional devices as described above, and it is a wow and flutter measurement device that can measure wow and flutter with high precision in a wide frequency range. The purpose is to provide.

A further object of the present invention is to provide a wow and flutter measurement device that can suppress the influence of interference signals and provide accurate measurement values even for signals under measurement with poor S/N ratios.

[Summary of the idea]

In order to achieve the above-mentioned object, the present invention includes a variable bandpass filter that changes the passing frequency region according to the frequency of the input signal under test, and a variable bandpass filter that limits the amplitude of the signal under test output from the variable bandpass filter. a frequency-to-voltage converter that converts the signal output from the amplitude limiter into a voltage by changing a conversion ratio in conjunction with the frequency change of the variable bandpass filter;
This device is characterized by comprising a sensitivity corrector that corrects the sensitivity to the output from the voltage converter, and a display meter that displays a measured value in accordance with the output from the sensitivity corrector.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 2, the wow and flutter measuring device includes a variable bandpass filter 11, an amplitude limiting amplifier 12, a frequency-voltage converter 13, and a sensitivity corrector 1.
4 and a display meter 15 are connected in series. The input signal to be measured is input to the input terminal 16.
First, the impedance is converted by the impedance converter 17 according to various inputs. The output from the impedance converter 17 is then transmitted to the variable bandpass filter 11. This variable bandpass filter 11 includes a high-pass circuit section 21 that is configured of a capacitor group 25 and a variable resistor 27 and that passes signals in a high frequency region.
and a low-pass circuit section 22 that is configured by a variable resistor 28 and a capacitor group 26 and passes signals in a low frequency region. The capacitor group 25 included in this high-pass circuit section 21 includes a plurality of, for example, four capacitors 25 with different capacities.
A, 25B, 25C, and 25D, and by switching with a switch 23, it is possible to roughly change the cut-off frequency step by step with a relatively large frequency difference. Furthermore, by changing the resistance value of the variable resistor 27, it is possible to continuously adjust the cut-off frequency within a relatively narrow range centered on each of the frequencies switched in stages. There is. Similarly, in the low-pass circuit section 22, the capacitor group 26 includes a plurality of, for example, four capacitors 26A, 26 with different capacities.
By changing the switch 24, the cut-off frequency can be changed stepwise with a relatively large frequency difference, and by changing the resistance value of the variable resistor 28. Therefore, it is possible to continuously adjust the cut-off frequencies within a relatively narrow range centered on each frequency that has been switched stepwise. Therefore, by combining the high-pass circuit section 21 and the low-pass circuit section 22, a bandpass filter characteristic that allows only signals in a specific frequency region to pass can be obtained. That is, by adjusting the changeover switches 23, 24 and variable resistors 27, 28 of the variable bandpass filter 11,
It is now possible to select to pass only input signals in a specific frequency range continuously over a wide band.

In this way, the signal under test is converted into a signal with almost only frequency components near the measurement frequency by the variable bandpass filter 11, and the amplitude of the input signal is further limited by the amplitude limiting amplifier 12.

The signal output from this amplitude limiting amplifier 12 is then transmitted to a frequency-voltage converter 13. This frequency-voltage converter 13 is also called a frequency detector or an FM demodulator, and various circuit configurations are known. The configuration of a so-called pulse count detector having a circuit 32 as a main part is shown. The capacitor 34 that becomes a part of the time constant circuit of the monostable multivibrator 31 is composed of a plurality of, for example, four capacitors 34A, 34B, 34C, and 34 having different capacities.
D can be selected by a changeover switch 33. Similarly, regarding the integrating circuit 32 consisting of a resistor 35 and a capacitor 36,
The capacitor 36 is, for example, four capacitors 36.
A, 36B, 36C, and 36D can be selected by a changeover switch 37. Here, if the changeover switches 33 and 37 are selected and set separately from the changeover switches 23 and 24 of the variable bandpass filter 11, the changeover of the variable bandpass filter 11 can be performed in response to the frequency of the input signal under measurement. This results in the complication of setting the frequency range of , and then setting the frequency-voltage converter 13, which leaves a problem in terms of operability. Therefore, these changeover switches 33, 37
is switched in conjunction with the frequency range switching operation described above, and simultaneously switches the pass frequency range of the variable bandpass filter 11 and simultaneously switches the conversion ratio of the output signal voltage to the input signal frequency of the frequency-voltage converter 13. It is designed to be appropriate in the specified frequency range. In this way, the changeover switches 33 and 37 in the frequency-voltage converter 13 are connected to the variable bandpass filter 11.
The frequency range of the variable bandpass filter 11 is set in accordance with the frequency of the input signal to be measured, and the frequency range of the frequency-voltage converter 13 is also set according to the frequency of the input signal to be measured. There is no need to make separate selection settings, resulting in extremely good operability.

Furthermore, by changing the resistance value of the variable resistor 41 of the sensitivity compensator 14, the input signal to be measured output as a voltage by the frequency-voltage converter 13 can be adjusted to the reference voltage while looking at the sensitivity compensation meter 42. adjusted to match. That is,
This is due to the following reasons. The voltage output from the frequency-voltage converter 13 changes linearly depending on the frequency of the signal under test, as shown in FIG. By the way, the effective value of wow/flatter W is given by the signal frequency as ₀ and the maximum fluctuation frequency deviation as Δ ₀ . It is expressed by the first equation: Therefore, the wow and flutter W ₁ at a certain frequency ₁ is generated from the DC component V 1 and the AC component V ₁ of the voltage output from the frequency-voltage converter 13 _. It is expressed by the second equation. Here the frequency is
2 ₁ and the wow/flatter is W ₁ , the DC component of the output voltage is 2V ₁ ,
The AC component is _2v1 . In other words, wow
Even if the value of the flutter is the same, if the frequency of the signal to be measured differs, the voltage of the AC component will vary in proportion to the frequency of the signal to be measured. Therefore, in order to display the measured values of wow and flutter based on the amplitude of the voltage of the AC component, it is necessary to step up or drop the voltage of the DC component to the reference voltage to always maintain the same voltage. There is. Therefore, it is necessary to make the voltage output from the frequency-voltage converter 13 match the reference voltage by the sensitivity corrector 14.

In this way, only the AC component of the sensitivity-corrected signal is transmitted to the display meter 15 through a detector, amplifier, etc. (not shown), so that the measured values of wow and flutter can be directly read.

By the way, the variable resistor 41 of the sensitivity corrector 14
are interlocked with the variable resistors 27 and 28 of the variable bandpass filter 11, making it possible to simultaneously adjust the cutoff frequency of the input signal and correct the sensitivity of the output signal in accordance with the measurement frequency.

In the embodiment described above, it is possible to measure wow and flutter over a wide frequency range, and the variable bandpass filter 11 converts the frequency components of the input signal into a signal containing only frequency components near the measurement frequency. Therefore, it is possible to measure wow and flutter with high precision even for a signal under test with a poor S/N ratio without being affected by interference signals.

Furthermore, in the above embodiment, the changeover switches 23 and 24 of the variable bandpass filter 11, the switches 33 and 37 of the frequency-voltage converter 13, and the variable resistors 27 and 28 of the variable bandpass filter 11 are used.
Since the variable resistor 41 of the sensitivity corrector 14 is linked with the variable resistor 41 of the sensitivity corrector 14, it can be easily switched in accordance with the measurement frequency, and the operability is extremely good.

In the above embodiment, when measuring the wow and flutter of an audio product such as a tape recorder, an auditory correction filter is connected between the sensitivity corrector 14 and the display meter 15 to provide a filter that is well suited to the senses of the ear. It is also possible to display it as a hearing correction effective value.

Furthermore, the present invention is not limited to the above-mentioned embodiments, and for example, the variable bandpass filter 1
If the configuration of No. 1 is equivalent to the above embodiment, the same effects can be obtained.

[Effect of idea]

According to the present invention, the variable bandpass filter prevents the input signal to be measured from being transmitted to the frequency-voltage converter with a wide band, so even if the signal to be measured has a poor S/N ratio, noise in the measurement signal can be reduced. Accurate measurement values that do not include other interfering signals can be obtained, and a highly reliable wow and flutter measuring device can be provided.

Therefore, it is possible to stably measure not only rotational unevenness of a tape recorder but also uneven rotation of a record player, rotational unevenness of a servo motor, etc. with any input signal to be measured at any frequency. becomes possible.

Furthermore, in the present invention, the frequency of the input signal under measurement is controlled by a frequency-voltage converter that converts the signal output from the amplitude controller into a voltage by changing the change ratio in conjunction with the frequency change of the variable bandpass filter. This eliminates the hassle of setting the frequency range of the variable bandpass filter and then setting the frequency-to-voltage converter accordingly, and provides a wow/flatter measurement device with extremely good operability. can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional wow and flutter measuring device. Fig. 2 is a block circuit diagram showing the configuration of one embodiment of the wow and flutter measuring device of the present invention, and Fig. 3 is the relationship between the frequency of the signal to be measured input to the frequency-voltage converter and the output voltage output. This is a graph showing. 11... Variable band pass filter, 12... Amplitude limiting amplifier, 13... Frequency-voltage converter, 1
4... Sensitivity corrector, 15... Display meter.

Claims (1)

[Scope of utility model registration request] a variable bandpass filter that changes the passing frequency region according to the frequency of the input signal under test; an amplitude limiting amplifier that limits the amplitude of the signal under test output from the variable bandpass filter; a frequency-voltage converter that converts a signal into a voltage by changing a conversion ratio in conjunction with a frequency change of the variable bandpass filter; a sensitivity corrector that corrects sensitivity to the output from the frequency-voltage converter; A wow/flatter measuring device comprising a display meter that displays a measured value in response to the output from the sensitivity corrector.