JPH06208707A - Magnetic signal reader - Google Patents

Abstract

PURPOSE:To obtain a signal having an excellent S/N ratio by installing a first electromagnetic conversion element reading magnetism on a magnetic recording body and a second electromagnetic conversion element at a position being not subject to the effect of magnetism on the magnetic recording body and mounting a comparator outputting the differential section of both output values as an electric signal. CONSTITUTION:A first MR element 1 is arranged near a position, where a magnetic recording body is passed, and a second MR element 2 is disposed at a position being not subject to the effect of the magnetism of the magnetic recording body in the vicinity of the element 1. The element 1 is connected to a constant current circuit 5a, constant currents Is1 flow, and voltage corresponding to the impedance of the element 1 is generated at a point (a). An AC section is extracted by a coupling capacitor 3 at a voltage value displayed at the point (a), and the value is inputted at the + terminal of a differential amplifier 6. The element 2 is connected to a constant current circuit 5b, and controlled so that constant currents Is2 flow, a value corresponding to the impedance of the element 2 is displayed at a point (b), and the AC section is extracted by a coupling capacitor 4 at the voltage value and input at the terminal of the amplifier 6. The differential section of the voltage values (a) and (b) is amplified by the amplifier 6, and a signal being not subject to the effect of noises is output to an outputted terminal (c).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic signal reader for converting magnetism on a magnetic recording medium into an electric signal.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a configuration of a main part of a conventional magnetic signal reading device.

An MR element (electromagnetic conversion element) 11 whose impedance changes according to the strength of a magnetic field on a magnetic recording medium (such as a magnetic tape) is connected to a constant current circuit 12. A constant current Is is applied to the MR element 11 by the constant current circuit 12.
Flows, and the voltage at point a changes according to the impedance of the MR element 11. This voltage value (a) has an AC component extracted by the coupling capacitor 13 and amplified by the amplifier 14.

[0004]

By the way, recent magnetic recording bodies have been narrowed in track in response to the demand for multi-channels. For this reason, the signal level becomes small, the wiring becomes thin and the wiring impedance becomes high, and the S / N ratio becomes poor. In addition, S /
The N ratio was getting worse.

An object of the present invention is to eliminate noise and remove S /
It is an object of the present invention to provide a magnetic data reader capable of obtaining a signal with a good N ratio.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a magnetic signal reading device for converting the magnetism on a magnetic recording body into an electric signal, and a first electromagnetic conversion element for reading the magnetism on the magnetic recording body, A second electromagnetic conversion element disposed near the first electromagnetic conversion element and at a position on the magnetic recording body that is not affected by magnetism; an output value of the first electromagnetic conversion element and a second electromagnetic conversion element; And a comparator that compares the output value of the conversion element and outputs the difference as an electric signal.

[0007]

The first electromagnetic conversion element according to the present invention outputs a value obtained by adding the value corresponding to the magnetism on the magnetic recording medium and the value corresponding to the amount of various noises. Further, since the second electromagnetic conversion element is arranged in the vicinity of the first electromagnetic conversion element and at a position not affected by magnetism on the magnetic recording body, the second electromagnetic conversion element contains the output value of the first electromagnetic conversion element. A value corresponding to the noise amount that is almost equal to the noise amount is output. Therefore, when comparing the output value of the first electromagnetic conversion element with the output value of the second electromagnetic conversion element, the output of this comparator is almost the output corresponding to only the magnetism recorded on the magnetic recording medium. (Signal) is obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the essential structure of a magnetic signal reader according to an embodiment of the present invention.

The first MR element 1 is arranged near the position where a magnetic recording medium such as a magnetic tape passes. The second MR element 2 is arranged in the vicinity of the first MR element 1 and at a position on the magnetic recording body which is not affected by magnetism. For example, as shown in FIG. 3, the magnetic head 9 may be provided on the side portion 8 of the position 7 where the first MR element is installed,
Further, it may be arranged near the magnetic head. First MR
The element 1 is connected to the constant current circuit 5a and is controlled so that the constant current Is1 flows, and the first MR element 1 is connected to the point a.
A voltage corresponding to the impedance of is generated. At this time, the voltage value appearing at the point a is a value obtained by superimposing a value corresponding to various noises on a value corresponding to the magnetic data on the magnetic recording medium. The voltage value (a) is extracted as an alternating current component by the coupling capacitor 3 and the value is input to the + terminal of the differential amplifier 6.

The second MR element 2 is connected to the constant current circuit 5b and is controlled so that the constant current Is2 flows, and a value corresponding to the impedance of the second MR element appears at point b. The voltage value appearing at the point b is determined by the first MR element 1
It is a value corresponding to a noise amount almost equal to the noise input to. An alternating current component of this voltage value (b) is taken out by the coupling capacitor 4, and the value is input to the-terminal of the differential amplifier 6.

As a result, the differential amplifier 6 has (a),
Only the difference corresponding to (b), that is, the value corresponding to the magnetic signal component on the magnetic recording medium is amplified, and a signal that is hardly affected by noise is output to the output terminal c.

[0012]

According to the present invention, noise can be cut when reading the magnetism on the magnetic recording medium, and the S / N ratio can be reduced.
A signal with a good ratio can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a magnetic data reading device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a main configuration of a conventional magnetic data reading device.

FIG. 3 is a diagram showing an arrangement example of a second MR element (magnetic conversion element).

[Explanation of symbols]

 1 1st electromagnetic conversion element 2 2nd electromagnetic conversion element 3, 4 coupling capacitors 5a, 5b constant current source 6 differential amplifier

Claims (1)

[Claims] 1. A magnetic signal reading device for converting the magnetism on a magnetic recording medium into an electric signal, comprising: a first electromagnetic conversion element for reading the magnetism on the magnetic recording medium; and a first electromagnetic conversion element. Comparing the output value of the second electromagnetic conversion element and the output value of the second electromagnetic conversion element with a second electromagnetic conversion element arranged in the vicinity and at a position not affected by magnetism on the magnetic recording body And a comparator for outputting the difference as an electric signal, and a magnetic signal reader.