JPH01267802A - Measuring instrument for magnetic tape erasing ratio - Google Patents

Abstract

PURPOSE:To easily measure the erasing ratio of a magnetic tape with good accuracy at low cost by detecting synchronously the reproducing output signal of a second channel by a synchronization detecting means with the reproducing output signal of a first channel track as a synchronizing signal and comparing this synchronization detection output signal with an erasing current. CONSTITUTION:A signal having a prescribed frequency is recorded on the first channel track and a second channel track on the magnetic tape. The synchronization detecting means detects synchronously the reproducing output signal of the second channel track with the reproducing output signal of the first channel as the synchronizing signal, the synchronization detection output signal is compared with the erasing current and the erasing ratio is compared. Consequently, a dynamic range can be widened without using such as expensive measuring instrument as a spectrum analyzer. Thus, the erasing ratio can be easily measured with good accuracy at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic tape erasure rate measuring device for measuring the erasure rate of a magnetic tape.

[Conventional technology]

The erasure rate of a magnetic tape is an important value that indicates the characteristics of the magnetic tape, and can predict the recording and reproduction characteristics of audio signals and video signals. The dependence of the erasing rate on the erasing current can be used to determine the variation in magnetic properties, orientation, etc. of the magnetic powder used in the magnetic tape.

In a video tape recorder, an IKHz signal recorded on a linear audio track is erased by an erasing head using a predetermined erasing current, and the erasure rate is defined as the ratio of the unerased signal level to the recorded level. This erasure rate is usually 60
A value of dB or more is required.

By the way, the erasure rate measuring device for measuring the erasure rate is
In order to obtain a sufficient measurement range, it is necessary to have a dynamic range of about 80 dB.

Conventional measuring devices have mainly used a method of increasing and recording the residual level in stages.

There is also a method of measuring using a spectrum analyzer. [Problem to be solved by the invention] However, conventionally, when using a pen recorder,
When the residual level becomes low, it is necessary to change the sensitivity using a sensitivity changeover switch. Therefore, there was a problem that the relationship between the erasing rate and the erasing current could not be displayed on the -sheet of recording paper. In addition, a spectrum analyzer can detect a signal change of 80 dB in lunges, but it is an expensive measuring device.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a magnetic tape erasure rate measuring device that can easily and accurately measure the erasure rate of a magnetic tape at low cost.

[Means to solve the problem]

Means for achieving the above object in the present invention is to record signals of a predetermined frequency on first and second channel trunks on a magnetic tape, and to synchronize the reproduction output signal of the recorded signal on the first channel track. A synchronous detection means for synchronously detecting the reproduced output signal of the recording signal of the second channel track as a signal is provided, and the erasure rate is measured by comparing the synchronous detection means signal of the synchronous detection means with the erasure current. The present invention relates to a magnetic tape erasure rate measuring device characterized by the following features.

[Effect]

In the above configuration, the synchronous detection means uses the reproduced output signal of the first channel track as a synchronous signal to synchronously detect the reproduced output signal of the second channel track, and compares this synchronous detection output signal with the erase current to determine the erasure rate. We are trying to measure it.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the circuit configuration, and shows the case where the circuit is applied to a video tape recorder having a two-channel linear audio trunk. 3 is an erasing head for the first channel track, 2 is a recording/reproducing head for the first channel track, 3 is an erasing head for the second channel trunk, and 4 is a recording head for the second channel track.

This is a dual-purpose playback head. 5 is a recording/playback switching switch for the erasing head 1; 6 is a recording/playback switching head for the recording/playback head 2; 7 is a recording/playback switching switch for the erasing head 3; 8 is a recording/playback head 4 recording and playback switching switches, which are interlocked with each other. Reference numeral 9 denotes an erasing signal generator built into the video tape recorder, which generates an erasing signal A of 65KI (z) shown in FIG. , 1o is an erasure signal generator which sends out an erasure signal B of 65 KHz whose amplitude gradually increases as shown in FIG. 2(B). 11 is an oscillator. , 12 is an amplifier connected to the output side of the oscillator 11, which generates a signal C which is a sine wave of a predetermined frequency, for example, IKHz, as shown in FIG. It is designed to supply the recording/reproducing head 2.4.

The playback output of the recording/playback head 2 is controlled by the selector switch 6.
, IKHz is supplied to a comparator 14 via a bandpass filter 13.

On the other hand, the reproduction output of the recording/reproducing head 4 is supplied to an amplifier 16 via a changeover switch 8 and an IKHz bandpass filter 15.

Reference numeral 17 denotes the same M detector, which uses a signal (D) obtained by converting IKHz into a rectangular wave as shown in FIG. The obtained 1KIIz sine wave signal C is synchronously detected. 18 is an integrator connected to the output side of the synchronous detector 17, 19 is a logarithmic amplifier connected to the output side of the integrator 18, and the output side of the logarithmic amplifier 19 is the Y-axis input side of the X-Y recorder 2o. It is connected to the. 21 is an erasure signal level detector connected to the output side of the erasure signal generator 1o. The output side of this level detector 21 is connected to the X-axis input side of the XY recorder 2o.

Next, the operation of one embodiment of the present invention having the above configuration will be described.

First, the changeover switches 5.6 and 7.8 are respectively switched to the recording side to set the recording mode. Then, the erasing signal A from the erasing signal generator 9 shown in FIG. 2(A) is supplied to the erasing heads 1 and 4 of each channel to perform erasing, and the sine wave from the oscillator 11 shown in FIG. 2(C) A certain signal C is supplied to the recording/reproducing head 2.4 and recorded on each channel track.

After this recording is completed, the magnetic tape is rewinded using the switch 5.
, 6, 7.8 are switched to the playback side to set the playback mode. In the playback mode, the erase signal generator 10 generates a signal from the erase signal generator 10 in FIG.
) is supplied to the erasing head 3 via the switch notch 7. Therefore, the erase head 3 gradually erases the recorded signal on the second channel trunk.

The recorded signal thus erased is reproduced by the recording/reproducing head 4. In this playback state, erase head 3 and recording are performed.

Since the read/write head 4 is extremely close to the read/write head 4, the time difference between the read signal and the erase signal can be ignored. The signal C which is a 1 KHz sine wave obtained at the output side of the filter 13 is converted by the comparator 14 into a rectangular wave output signal as shown in FIG. 2(D). The synchronous detector 17 uses the output signal as a synchronous signal and synchronously detects the signal C from the amplifier 16 obtained from the second channel track to obtain the detected output signal E shown in FIG. 2(E). This output signal E is integrated by an integrating circuit 18 to obtain a smoothed output signal F shown in FIG. 2(F). This output signal E is logarithmically amplified by a logarithmic amplifier 19 and supplied to the Y-axis input side of the X-Y recorder. At the same time, the erasing signal B of the erasing signal generator 10 is detected by the detector 21 and is converted into an output signal G that gradually increases as shown in FIG. 2 (G). is supplied to Therefore, in the XY recorder, the degree of erasing with respect to the erasing current is measured.

〔Effect of the invention〕

As described above, according to the present invention, the synchronous detection means synchronously detects the reproduced output signal of the second channel track using the reproduced output signal of the first channel as a synchronizing signal, and compares this synchronously detected output signal with the erase current. Magnetic tape erasure rate measurement allows you to measure the erasure rate of magnetic tape, which can increase the dynamic range without using expensive measuring equipment such as a spectrum analyzer, and is easy to measure at low cost. equipment can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram showing waveforms of each circuit component in FIG. 1. 1.3... Erasing head, 2.4... Recording/reproducing head, 9.10... Erasing signal generator, 11... Oscillator, 14... Comparator, 17... Synchronous detector, 18...
... Integrator, 19... Logarithmic amplifier, 20...
. . . X-Y recorder, 21 . . . Erasing signal level detector. Figure 2 (A) (B) (C) Enemy (D) (E) (F)

Claims (1)

[Claims] A signal of a predetermined frequency is recorded on the first and second channel tracks on the magnetic tape, and the recorded signal on the second channel track is reproduced using a reproduction output signal of the recorded signal on the first channel track as a synchronization signal. A magnetic tape erasure rate measuring device, comprising: a synchronous detection means for synchronously detecting an output signal; and an erasure rate is measured by comparing the synchronous detection output signal of the synchronous detection means with an erase current.