JPH0436663A - Frequency variation measuring instrument - Google Patents

Abstract

PURPOSE:To take a measurement stably and efficiently in a short time by switching a measuring means from a dummy signal generating means which generates nearly the same dummy signal as a measurement signal to an object to be measured and performing measuring operation. CONSTITUTION:The dummy signal generating means 1 generates a sine wave of preset center frequency at all times. Further, the measuring means 4 is connected normally to the means 1 and composed of a frequency discriminating circuit 5 and an indication meter 5, which detects how much the signal outputted from a switching means 3 shifts from the center frequency and outputs a voltage corresponding to the deviation. Then when a measurement signal is outputted from the object 2 to be measured, a control means 7 switches the means 3 through the means 3 to connect the output of the object 2 to the means 4. In this case, when the frequencies of the dummy signal and measurement signal are close enough, the output of the circuit 5 included in the means 4 does not vibrate greatly and a stable measurement result is obtained in a short time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a frequency change measuring device that measures changes in the frequency of a measurement signal generated from an object to be measured. This invention relates to a frequency change measuring device that is useful for applications.

[Conventional technology]

A common problem with devices that run tape by mechanical means, such as tape recorders, is how to reduce tape speed fluctuations.

In order to improve such tape speed fluctuations, it is necessary to measure tape speed fluctuations. To measure tape speed fluctuations, a speed fluctuation measuring device is used, which is a type of frequency change measuring device that measures changes in frequency.

To measure the speed fluctuation of a tape using a speed fluctuation measuring device, a tape on which a sine wave of about 3 KHz is recorded is played back with a tape recorder. The reproduced signal is input to a speed fluctuation measuring device. The speed variation measuring device includes a frequency discrimination circuit. The frequency discrimination circuit outputs a signal corresponding to the frequency deviation of the measurement signal reproduced from the tape recorder with respect to 3 KHz. By measuring the output of this frequency discrimination circuit, it is possible to measure variations in the speed of the tape recorder.

[Problem to be solved by the invention]

By the way, conventional frequency change measuring devices have had a problem in that when a measurement signal from an object to be measured is suddenly input, the output of the frequency change measuring device fluctuates rapidly and meaninglessly. The reason for this is a characteristic peculiar to frequency discrimination circuits; when the frequency suddenly changes or when an input signal suddenly appears where there is no input signal, the output oscillates violently.

As a result, there is a problem in that measurement by the frequency change measuring device cannot be performed until the output of the frequency change measuring device becomes stable after the measurement signal is input.

The present invention has been made by focusing on such conventional problems, and it is an object of the present invention to provide a means change measuring device that can obtain stable measurement results in a short time even if a measurement signal is suddenly input to the frequency change measuring means. The purpose is to

[Means to solve the problem]

In order to achieve this object and solve the above-mentioned problems, the present invention provides a dummy signal generating means that generates a dummy signal that is substantially the same as a measurement signal, and switches the output of the measurement object and the output of the dummy signal generating means. a switching means; a measuring means for measuring a change in frequency of an output signal of the switching means; and a measuring means for starting generation of a measurement signal from the object to be measured, and switching the switching means from the dummy signal generating means to the object to be measured. This is a frequency change measuring device for measuring changes in the frequency of a measurement signal generated by an object to be measured.

[For production]

With the above configuration, the dummy signal generating means always generates a sine wave dummy signal of a constant frequency. The measuring means for measuring frequency changes is usually connected to the dummy signal generating means. When a measurement signal is generated, the switching means switches the measuring means from the dummy signal generating means to the object to be measured. Then, from the perspective of the measuring means, the signal input to the measuring means will not change suddenly. , Therefore, the frequency change measuring device becomes stable quickly.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

1 in the figure is a dummy signal generating means.

The dummy signal generating means 1 generates a sine wave of a preset frequency. If speed fluctuations of a tape recorder are to be measured, this frequency is standardized and is approximately 3 KHz. 2 is an object to be measured. The measurement object 2 is
For example, it is a tape recorder that plays back a tape for measuring speed fluctuations. The measurement object 2 generates a measurement signal that is a signal to be measured. 3 is a switching means. The switching means 3 switches between the measurement signal generated by the measurement object 2 and the dummy signal generated by the dummy signal generation means 1. Reference numeral 4 denotes a measuring means for measuring changes in the frequency of the signal output from the switching means 3. The measuring means 4 includes, for example, a frequency discrimination circuit 5 and an indicator meter 6. The frequency discrimination circuit 5 detects how much the signal output from the switching means 3 deviates from the center frequency (for example, 3 KHz), and outputs a voltage corresponding to the frequency deviation.

The indicator meter 6 indicates a value corresponding to the output voltage of the frequency discrimination circuit 5. 7 is a control means. The control means 7 is
Both the measurement object 2 and the switching means 3 are controlled. The measurement object 2 outputs a measurement signal according to a control signal from the control means 7. The switching means 3 connects the output of the dummy signal generating means 1 to the measuring means 4 when no output signal is output from the measurement object 2 according to the output of the control means 7. Furthermore, when the measurement signal is output from the measurement object 2, the switching means 3 connects the output of the measurement object to the measurement means 4.

According to the above configuration, initially, no measurement signal is output from the measurement object 2, and the output of the dummy signal generation means 1 is connected to the measurement means 4. The dummy signal is
Since it is a sine wave with a stable frequency, the indicator meter 6 of the measuring means 4 indicates zero.

Next, when the control means 7 outputs a measurement signal from the measurement object 2, the switching means 3 connects the output of the measurement object 2 and the input of the measurement means 4.

Then, from the perspective of the measuring means 4, the dummy signal is first input, and then the measurement signal is input. If the frequencies of the dummy signal and the measurement signal are sufficiently close, the output of the frequency discrimination circuit 5 included in the measurement means 4 will not oscillate violently.

In this way, stable measurement results can be obtained in a short time.

FIG. 2 is a block diagram showing a second embodiment of the invention. The difference from the first embodiment is that the control means 7 includes a control circuit 9 and a timer means 8. The control circuit 9 is a circuit equivalent to the control means 7 of the embodiment shown in FIG. The timer means 8 is connected between the control circuit 9 and the switching means 3. The timer means 8 delays the output of the control circuit 9 and transmits it to the switching means 3.

This timer means 8 functions to delay the switching of the switching means 3 until the measurement object 2 starts outputting the measurement signal. Then, even if the measurement target 2 rises slowly, the measuring means 4 can perform stable measurements.

FIG. 3 is a block diagram showing a third embodiment of the present invention. The difference from the embodiment shown in FIG. 1 is that the control circuit 7 includes a frequency detection means 10 and a control circuit 11. The frequency detection means 10 measures the frequency of the measurement signal of the measurement object 2, and outputs a signal to the control circuit 11 when the frequency of the measurement signal reaches a preset frequency.

The control circuit 11 controls the measurement object 2 and the switching means 3. The control circuit 11 first puts the measurement object 2 into a state where a measurement signal is output. Then, the frequency detection means 10 starts measuring the frequency of the measurement signal. When the measurement signal reaches a preset frequency, the control circuit II switches the switching means 3. By doing so, even if there are variations in the rise of the object to be measured, the measuring means 4 can perform stable measurements.

〔effect〕

As described above, by implementing the present invention, it is possible to obtain a frequency change measuring device that can efficiently measure frequency fluctuations.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a block diagram showing a second embodiment of the invention, and FIG. 3 is a block diagram showing a third embodiment of the invention. 1...Dummy signal generation means, 2...Measurement object, 3...Switching means, 4...
- Measuring means, 5... Frequency discrimination circuit, 6...
... Indication meter, 7 ... Control means, 8 ...
. . . Timer means, 9 . . . Control circuit, 10.
. . . Frequency detection means, 11 . . . Control circuit.

Claims (3)

[Claims] (1) A frequency change measuring device for measuring a change in frequency of a measurement signal generated by an object to be measured, comprising: dummy signal generating means for generating a dummy signal substantially the same as the measurement signal; and the object to be measured. switching means for switching between the output of the dummy signal generating means and the output of the dummy signal generating means; measuring means for measuring a change in frequency of the output signal of the switching means; 1. A frequency change measuring device comprising: control means for controlling switching means from said dummy signal generating means to said measuring object. (2) In the frequency change measuring device according to claim 1, the control means includes a timer means, and after first starting to generate a measurement signal from the measurement object, the timer means Delay by the set time,
A frequency change measuring device configured to switch the switching means. (3) In the frequency change measuring device according to claim 1, the control means includes a frequency measuring means for measuring the frequency of the measurement signal generated by the measurement object, and first, the control means measures the frequency of the measurement signal generated by the measurement object. After starting to generate a measurement signal from the measuring device, the frequency measurement means measures the frequency of the measurement signal, and when the frequency of the measurement signal reaches a preset frequency, the switching means is switched. Frequency change measurement means.