JPS601617A - Test method of magnetic head - Google Patents

Abstract

PURPOSE:To decide the quality of a magnetic head with high accuracy by converting the peak level of each read signal read out by a reading head into the digital value and adding these peak levels for storage. CONSTITUTION:The signal obtained from a reading head is supplied through an input and compared with the analog output of an A/D converter 13 by a comparator after rectification 1. The result of this comparison is sent to a counter 11. When the output of a rectifier 1 which is compared by the comparator 10 is larger than the output of the converter 13, the output of the comparator 10 is equal to the signal to be added to a counter 11. At the same time, the value equivalent to the difference of both outputs is delivered. While the output of the comparator 10 is equal to the signal to be subtracted from the counter 11 if the outut of the rectifier 1 is smaller than the output of the converter 13. At the same time, the value equivalent to the difference of both outputs is delivered. The counter 11 is an up/down counter and performs counting with addition/subtraction given to the output of the comparator 10 with the clocks produced every zero cross point. Then the counter 11 sends its count value to a multiplexer 12 as well as to an adder 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a characteristic testing device for a magnetic head used in a magnetic tape device, etc. In particular, the peak level of the output of the magnetic head is added multiple times, and this value is used to test the characteristics of the magnetic head. This invention relates to a magnetic head testing method for determining the acceptability of magnetic heads.

(b) Prior Art and Problems A magnetic head for writing/continuation used in a magnetic tape device or the like writes on a recording medium, immediately reads it out, and integrates the peak level to judge whether it is good or bad. This is because when a recorded signal is repeatedly read out many times, it is demagnetized and the readout level decreases. Therefore, the read level immediately after recording on the recording medium is required, but the magnetic head used in a magnetic tape device has a write head and a read head as a pair, and when the write head is writing, Since noise induced from the write head enters the read head, it is necessary to devise ways to write signals. For this purpose, a signal is recorded on the recording medium by a write head, the write operation is stopped just before the part of the recording medium where the signal is recorded reaches the read head, and immediately after the read head completes reading the record, the write operation is started again. I do. By repeating this action,
The peak level of the analog signal read from the write signal is integrated while avoiding the noise accompanying the write operation.

By doing this, it is possible to obtain an integral value of the signal from which noise during writing has been removed.

FIG. 1 is a diagram illustrating a state when a recording medium on which a magnetic head test signal is written is read and a state in which the peak level of the signal is integrated. The part indicated by a in FIG. 1A shows the output of the read head when reading the portion of the recording medium on which the signal has been written, and the range indicated by b shows the part where writing is stopped. The range a is smaller than the distance that the recording medium travels between the write head F and the read head gap. When the peak level of the signal recorded as described above is integrated, the integration operation is stopped in the range that is not shown, so that the peak level of the signal is integrated using a curve as shown by C in FIG. 1B.

FIG. 2 is a block diagram showing an example of a conventional circuit that performs the above integration using analog values. A signal read from the read head enters from the input, is rectified by the rectifier 1, and enters the amplifier 3 via the switch 2-1. Switch 2-1 and switch 2-2 are switches that are inverted depending on the presence or absence of the signal. The signal amplified by the amplifier 3 is transferred to the capacitor C1.
As a result, the peak level of each waveform shown in FIG. 2 short-circuits the capacitor CI to discharge the previous integrated value.The integrated value stored in the capacitor CI enters the comparator 4, and is sent to the digital/analog converter (
The output of the comparator 4 is sent to the counter 5 until the comparison results are the same. The output of the counter 5 is converted to a digital/ab river cog converter 6.
sent to. Therefore, the output of the counter 5 is obtained by integrating the peak level of each block shown by a in FIG.
The integral value is sent out as a digital value as shown in . The counter 5 is an amplifier down counter and returns to zero within the range shown in the figure.

Integrating the peak level using the analog circuit shown in FIG. 2 has the drawback that it is not only expensive because the parts of the analog circuit are of good quality, but also uneconomical because the adjustment is of high quality.

(C) Purpose of the Invention The purpose of the present invention, in order to eliminate the above-mentioned drawbacks, is to provide a method for testing a magnetic helix using a digital circuit, which is economical and does not require adjustment and has good integration even during long-time integration. There is a particular thing.

(d) Structure of the Invention The structure of the present invention is such that a signal written multiple times intermittently by a write head on a magnetic recording medium is read by a successive read head, and the peak level of each read signal is added. A magnetic head test method for determining the quality of a magnetic head based on an added value, which converts the peak level of each readout signal read by the successive head into a digital value, and adds the peak levels of each signal. By memorizing the information, it is possible to judge whether the magnetic throat is good or bad.

(c) Embodiment of the Invention FIG. 3 is a block diagram of a circuit showing an embodiment of the invention. The signal read from the read head enters from the input,
It is rectified by a rectifier 1 and compared with an analog output from a digital/analog converter (D'/A) 13 in a comparator 10, and the comparison result is sent to a counter 11.

The output of rectifier 1 compared with comparator 1o is digital/
If it is larger than the output of analog converter 13, comparator 1o
The output is a signal to be added to the counter 11, and
A value corresponding to the difference is output, and if it is small, a signal to be subtracted and a value corresponding to the difference are output. The counter 11 is an amplifier down counter and is d in Fig. 1A.
The output of the comparator 1o is counted by addition/subtraction using a clock generated at each zero-crossing point of the signal shown by , and the counting result is sent to the multiplexer 12 and the adder 14. The multiplexer 12 sends the counting result to the digital/analog converter 13.
converts the counting result into an analog value and sends it to the comparator 10. Therefore, the counting result of the counter 11 shows the peak value of each signal waveform of d shown in FIG. 1A as a digital value. The adder 14 adds the contents of the register 15 to the count result of the counter 11 and causes the register 15 to store the result. register 15
The output of the adder 14 is stored in synchronization with the counter 11 by the clock. Therefore, the register 15 stores values obtained by integrating the peak values of each waveform for the number of signal waveforms d included in FIG. 1a. When the read head comes to the range indicated by b in FIG. 1A, the signal disappears and the clock stops, so the counter 11 holds the count up to that point. Therefore, in the range where the signal indicated by a is written, the peak value of each signal waveform indicated by d is sent out as a digital value. Therefore, as shown by e in FIG. 1B, the value of register 15 increases. Here, the total integral value obtained by integrating the number of blocks shown by a in FIG. To calculate the average value of the peak level, use register 15.
It is sufficient to divide the integral value of by the number N of signal blocks that have been integrated.

Therefore, a shift command is given from the terminal to shift the register 15 N times, and the average value of the peak level is sent out as a digital value from the output. In addition, when obtaining the average value of the peak level as an analog value, the multiplexer 12 selects register 1.
The average value of 5 is sent to the digital/analog converter 13, converted, and sent to the terminal E. Due to the response speed of the comparator 10, counter 11, and digital/analog converter 13 of this embodiment, the average value shown in FIG. The count value of the counter 11 may not be able to follow the peak value of the signal waveform indicated by d of A, but if the number N is increased, the error can be ignored.

(f) As described in detail, the present invention provides a digital integration method using an economical digital circuit that has good accuracy even during long-term integration and does not require adjustment, so its effects are great. There is something.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the write state of a magnetic head test signal and the state of integrating the peak level of the signal. FIG. 2 is a block diagram showing an example of a circuit that performs the above integration using conventional analog values. The figure is a block diagram of a circuit showing one embodiment of the present invention. 1 is a rectifier, 3 is an amplifier, 4 and 10 are comparators, 5.11
is a counter, 6.13 is a digital/analog converter,
12 is a multiplexer, 14 is an adder, and 15 is a register.

Claims (1)

[Claims] A magnetic recording medium that reads signals written multiple times intermittently by a write head on a magnetic recording medium using a successive read head, adds up the peak levels of each read signal, and determines the quality of the magnetic head based on this added value. A head testing method, wherein the peak level of each readout signal read by the successive head is converted into a digital value, and the peak level of each signal is added and stored to determine the quality of the magnetic head. A magnetic head testing method characterized by: