JPH0823922B2 - Magnetic disk write current measuring method and current measuring apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for measuring a magnetic disk write current value in a magnetic disk tester,
Specifically, it relates to measurement of an appropriate write current value.

[Prior Art] Magnetic disks and magnetic heads, which are widely used as information recording media, undergo various tests in the manufacturing process. One of them is to write an appropriate value of a write current before writing control information or test data. A measurement is made to determine

A conventional method for measuring an appropriate current will be described with reference to FIGS. 3 (a), (b), and (c). Magnetic disk 1 shown in FIG.
For a given track of, during the index (IND),
That is, the test signal is written in and read from the track by the write current Iw having a constant frequency shown in FIG. The relationship between the amplitude of the current Iw and the amplitude E _R of the read test signal in that case will be described. Figure (c)
At, the E _R increases steeply in proportion to the increase of Iw to some extent, and beyond that, it saturates to reach the peak value Ep and then gradually decreases. The reason for the decrease is that when Iw is excessively large, the magnetic field of the recording head is affected by the immediately preceding recording code and demagnetized. With the above characteristics, in the front of the saturated unstable changes greatly E _R by small changes in Iw, also exerts an adverse influence on the immediately preceding recording code when excessive, both undesirable. On the other hand, the current value Iw for the point q with a small change just after the peak point p
c is considered appropriate. The point q is defined by the intersection of the curve of the amplitude E _R and kEp obtained by multiplying the peak value Ep by an appropriate coefficient k smaller than 1. Conventionally, writing and reading for the same track are repeated a plurality of times using Iw as a parameter to obtain an E _R -Iw curve, the peak value Ep is obtained by visual observation, and this is multiplied by an appropriately determined coefficient k to obtain Iwc. How to determine is done.

[Problems to be Solved] In the conventional method for obtaining the appropriate current value Iwc as described above, writing and reading are performed for one track for each current value Iw, so that the number of tests is large and many are produced in the production factory. In the case where the measurement is performed by combining the magnetic disk and the magnetic head, the measurement takes a very long time and the data processing is not efficient. The reason why the data for one track of each current value is required for each current value is that the read signal may be accompanied by modulation due to distortion of the magnetic disk. This is because the average value is taken. On the other hand, if there is no modulation or if it is possible to correct the modulation, it is possible to obtain the above E _R -Iw curve by dividing the track into several and changing the current value for each. Therefore, the test time can be significantly shortened.

The present invention has been made in view of the above, and when the test signal has no modulation or can be corrected by a separate means, the test signal is written by changing the write current value for one round of the track. An object of the present invention is to provide a method for measuring an appropriate write current value and a measuring device for immediately outputting the appropriate current value.

[Means for Solving the Problem] The feature of the magnetic disk write current value measuring method of the present invention for achieving such an object is that a constant frequency at which the amplitude linearly increases in one round of the track of the magnetic disk. Write the test signal with the write current of the test signal, read the test signal from the track, detect the envelope signal of the read test signal and the peak value of the envelope signal, and a constant coefficient smaller than 1 with respect to the detected peak value. The voltage multiplied by is compared with the envelope signal voltage, and the write current value at the time of writing corresponding to the coincidence point of the two compared is set as an appropriate current value.

Further, the write current value measuring device for a magnetic disk according to the present invention is characterized in that a write current generator for generating a write current whose amplitude linearly increases in one round of a track for a test signal, and the write current generator for the track. Writing / reading circuit for writing the test signal generated by and reading the written test signal, an envelope detector for detecting the envelope signal of the read test signal, and a peak detection for detecting the peak value of the envelope signal , A multiplier that multiplies the peak value by a constant coefficient smaller than 1, a comparator that compares the output voltage of the multiplier and the envelope signal voltage, and outputs a match signal when both signal voltages match, and a match signal Accordingly, the current value generated by the write current generator at the write time corresponding to the coincidence time is It is intended and a proper current value detector output.

[Operation] By the way, the modulation by the magnetic disk is
This is due to the distortion of the disk, and there is a gradual fluctuation in one round of the track. Therefore, when a test signal is written by a write current having a constant frequency in which the amplitude linearly increases in one round of the track as in the above-described configuration, even if the amplitude is changed due to the modulation by the magnetic disk. Also, since there is an increase in the amplitude, the modulation is canceled by the increase in the amplitude.
As a result, fluctuations in the position of the peak point are not significantly affected. That is, by increasing the amplitude, it becomes possible to perform measurement without modulation.

As shown in FIG. 3 (c), the characteristic at the position beyond the peak point has a comparatively gentle curve, and even if there is a slight difference in the write current, it has little effect on the amplitude of the read signal. .

Therefore, the proper current value obtained by the above configuration can be used as it is as the proper current value.
In addition, even in the above case, it does not prevent that the correction is separately performed because there is modulation. In such a case, the envelope signal of the test signal undergoes a change in modulation, so it is simply
Measure the modulation change value in the lap,
It suffices to correct the comparison voltage at the coincidence point by the amount of modulation change at that time.

As a result, the measurement for one track is sufficient, and it is not necessary to average the measurement values for many tracks.

The operation of the above write current value measuring method will be described with reference to FIGS. 1 (a), (b) and (c). Figure (a)
At, the test signal is written by the write current Iw that linearly increases for one turn between the track indexes (IND). The amplitude ER of the read signal is shown in FIG. 6B, and its envelope signal voltage Ee is plotted on the horizontal axis at time t.
Is shown by the curve in FIG. Peak value Ep of voltage Ee
Is detected and the voltage kEp obtained by multiplying this by an appropriate coefficient k (0 <k <1) and the voltage Ee are compared, and the current value Iwc of FIG. It is an appropriate current value. That is, a proper current value can be obtained from the data of one track of the track.

The write current value measuring device realizes the above-described measuring method, and by the control of the microprocessor, the write current Iw that the amplitude output from the write current generator linearly increases is generated between the track index signals. The test signal is written. From the read signal, the envelope detector detects the envelope signal voltage.
Ee is detected. Furthermore, the peak value Ep is detected by the peak detector, the voltage kEp obtained by multiplying Ep by the coefficient k is compared with the voltage El by the multiplier, and the coincidence signal is output by the comparator at the coincidence time of both. The coincidence signal is input to the appropriate current value detector, and the current value of the write current generator at the time of input is immediately output as the appropriate current value.

[Embodiment] FIG. 2 shows a schematic block configuration of an embodiment of a magnetic disk write current value measuring method and measuring apparatus according to the present invention. According to a command from the microprocessor 2, a drive current is supplied from the drive controller 1a to the motor 1b to rotate the magnetic disk 1, and its index (IND) is detected by the index detector 1c. On the other hand, the current sweep generator 3 generates a write current whose amplitude increases linearly, and the condition for the current value is set by the microprocessor 2 in advance. A write current is generated starting from the index signal, a test signal is written by the magnetic head 1d through the write / read amplifier (R / W AMP) 4, and the process ends with the next index signal. After the end, the test signal is read by the magnetic head 1d, is input to the envelope detector 5 via the R / W AMP 4, and the envelope signal is detected. Then, the peak value of the envelope signal is detected by the peak detector 6,
The coefficient k is multiplied by the multiplier 7 and the comparator (COM
It is input to the + terminal of P) 8 and compared with the envelope signal input to the-terminal. When the two match, a match signal is output and transferred to the proper current value detector 9. The current value that increases from the current sweep generator 3 is constantly input to the proper current value detector 9, and the current value at the time of coincidence is detected and input to the microprocessor 2, and is output to the output unit 2a as the proper current value. Is displayed. It is needless to say that the coefficient k in the above is based on the numerical value of the conventional measuring method. Also,
The current sweep generation circuit 3 outputs a current signal that linearly increases in response to the index signal (IND) even in the read state, but since the write / read amplifier 4 is in the read state, The output signal is invalid. However, the current sweep generator circuit 3
The sweep current value of is added to the current value detector 9.

EFFECTS OF THE INVENTION As is apparent from the above description, in the write current measuring method for a magnetic disk according to the present invention, it is assumed that the test signal has no modulation, or
Assuming that the correction is performed as necessary, an appropriate value of the write current can be obtained by measuring one track.
In addition, the measuring instrument immediately outputs the obtained proper current value, which significantly shortens the measurement time that was required multiple times in the past, and improves the efficiency of measurement work in production plants that combine a large number of magnetic disks and magnetic heads. The effect is great.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the operation of a magnetic disk write current measuring method and a measuring apparatus according to the present invention, and FIG. 2 is a schematic block configuration diagram of an embodiment of a magnetic disk write current measuring method and a measuring apparatus according to the present invention. , (A), (b) and (c) of FIG. 3 are explanatory views of a conventional write current measuring method for a magnetic disk. 1 ... magnetic disk, 1a ... drive controller, 1b ... motor, 1c ... index detector, 1d ... magnetic head, 2
...... Microprocessor, 2a …… Output unit, 3 …… Current sweep generator, 4 …… R / W AMP, 5 …… Envelope detector, 6 …… Peak detector, 7 …… Multiplier, 8 ・ ・ ・… Comparator, 9 …… appropriate current detector.

Claims (2)

[Claims] 1. A test signal is written by a write current of a constant frequency whose amplitude linearly increases in one round of a track of a magnetic disk, the test signal is read from the track, and an envelope of the read test signal. A signal and a peak value of the envelope signal are respectively detected, the voltage obtained by multiplying the detected peak value by a constant coefficient smaller than 1 is compared with the envelope signal voltage, and the coincidence points of the both are compared. A method for measuring a write current value of a magnetic disk, characterized in that the write current value at the time of writing corresponding to is set to an appropriate current value. 2. A write current value measuring device for a magnetic disk, which writes a test signal to a track of a magnetic disk and reads the test signal from the track to measure an appropriate write current value. A write current generator that generates a write current whose amplitude linearly increases in one round, and a write / read that writes the test signal generated by the write current generator to the track and reads the written test signal. A circuit, an envelope detector for detecting an envelope signal of the read test signal, a peak detector for detecting a peak value of the envelope signal, and a multiplier for multiplying the peak value by a constant coefficient smaller than 1. , Comparing the output voltage of the multiplier with the envelope signal voltage A comparator that outputs a coincidence signal when both the signal voltages coincide with each other, and an appropriate current value detector that detects a current value generated by the write current generator at the write time corresponding to the coincidence time according to the coincidence signal. An apparatus for measuring a write current value of a magnetic disk, comprising: