JPS5858407A - Detecting circuit for projection of magnetic disc - Google Patents

Abstract

PURPOSE:To detect the munber of projections having varying heights without changing the number of revolutions of a floating head or a magnetic disc by providing a detecting element for elastic waves generated by collision against the projections to the floating head, and comparing the outputs thereof with the set thresholds of an amplitude discriminator. CONSTITUTION:A detecting element which detects elastic waves generated by collision against projections is provided to a floating head 1, and the outputs thereof are inputted to an amplitude discriminator. The signal waveforms of the detecting elements are as shown by Figure (b), and the peak values thereof change according to the extent of floating of the head 1 and the heights of projections 3-6. The peak values are beforehand prepared as data, and threshold values are set as shown by A, B, C of a figure (b). For the detection signals exceeding said values, pulses are formed like c-e, and are counted. Therefore the number of the projections differing in height is detected simply by changing the threshold values without changing the number of revolutions of the floating head or the magnetic disc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protrusion detection circuit for a magnetic disk that detects the number and size of protrusions using elastic waves generated by a collision between a floating head and a protrusion on a rotating magnetic disk.

Previously, it was only possible to determine the presence or absence of protrusions at the flying height of the floating head; to determine the number of protrusions of different heights, it was necessary to change the flying height of the floating head; to change the flying height, change the floating head. 1. The purpose of the present invention is to change only the threshold value of the amplitude discriminator without changing the rotation speed of the floating head or the magnetic disk. The objective is to obtain the frequency distribution according to the height of the protrusions.

The protrusion detection circuit for a magnetic disk of the present invention includes a floating head equipped with a detection element that detects an elastic wave generated by a collision between a floating helad and a protrusion on a rotating magnetic disk, and an output from this detection element. Input to amplitude discriminator and compare with set threshold.

The number and size of protrusions are detected by *W.

FIG. 1 is a diagram explaining the principle of the present invention. The detection element signal waveform generated by the collision between the floating head 1 and the protrusions 3 to 6 on the rotating magnetic disk 2 is as shown in FIG. 1(b).

The peak value of this signal is the flying height of the floating head 1 and the protrusion 3~
6 can be obtained depending on the height. The peak value of the detection signal based on the flying height and protrusion is prepared in advance as data, and based on this data, the person Φ) in Figure 1, B10
Set the threshold as follows. The detection signals exceeding the respective thresholds are subjected to pulse shaping as shown in FIGS. 1(C), (d), and (e), and the pulses are counted.

This allows us to know the size and number of protrusions.

(C) Those exceeding the threshold (surfacing height 6 or more) are 1
(d) exceeds the threshold B (flying height β ~ a)
(e) exceeds the threshold value C (flying height β ~
The case where there are four a) is shown.

According to the present invention, by changing only the threshold value of the amplitude discriminator without changing the number of rotations of the floating head or magnetic disk, it is possible to obtain a precision distribution according to the height of the protrusion.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention, (a) is a diagram showing a floating head and a magnetic disk protrusion, (C) (d) (@) is a diagram showing a Φ) line detection signal waveform and a threshold. FIG. 3 shows a pulse shaped for a signal that exceeds a threshold; A, 8%0...Threshold 1...
Floating head 2...Magnetic disk S~6...
····protrusion

Claims (1)

[Claims] A detection element is provided on the floating head to detect an elastic wave generated by a collision between the floating head and a protrusion on a rotating magnetic disk, and the output from this detection element is input to an amplitude discriminator.
A protrusion detection circuit for a magnetic disk, which detects the number and size of protrusions by comparing them with a set threshold value corresponding to the size of the protrusions.