JPS63257912A - Magnetic head evaluation device - Google Patents

Abstract

PURPOSE:To accurately measure a recording efficiency with a simple constitution by obtaining the magnetic saturation current of a head from the lowered point of an inductance value which is generated by means of the magnetic saturation of the magnetic head when the oscillation amplitude of an oscillator connected to the both ends of the coil in the head is changed. CONSTITUTION:The amplitude of the oscillator 11 is variable and if the amplitude is changed from large to small, an inductance falls from a prescribed current value by the magnetic saturation of the head 14. With the change in the oscillation amplitude of the oscillator, the change in the inductance value of the magnetic head is measured so as to obtain the magnetic saturation current of the head, and with the magnetic saturation current and the saturation magnetic flux density of a head core material, the recording efficiency of the magnetic head is measured. Thus, it comes to be unnecessary to fit a mechanism or the head for recording and reproduction and secondary winding becomes unnecessary, whereby the whole constitution is simplified and the recording efficiency can easily and efficiently be measured.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic head evaluation device for measuring the recording efficiency of a magnetic head used as a recording/reproducing head of a video tape recorder, etc., and evaluating the magnetic head. It is something.

[Prior Art] As an example of a conventional method for measuring and evaluating the recording efficiency of a magnetic head, for example, an evaluation called the two-speed modified method was announced by the NHK Broadcasting Technology Research Institute at the 1986 National Conference of the Television Society. There is a way. FIG. 3 is a graph showing the principle of measuring recording efficiency using the two-speed modified method, and FIG. 4 shows the basic configuration of the measurement.

In FIG. 3, (a) is a characteristic curve of the head reproduction output (e) when the recording current (i) is varied with the relative speed (V) between the recording medium and the head and the recording frequency (f), (
B) is a characteristic curve of the head reproduction output (e) when the recording current (i) is varied with the relative speed (2v) and the recording frequency (2f).

In FIG. 4, (41) is a magnetic recording medium such as a tape, and (42) is a magnetic head to be measured (hereinafter referred to as
(referred to as a magnetic head), (43) is a recording/reproducing signal switching switch, (44) is a swing I11! and a variable frequency oscillator, and (45) is a detector for detecting the playback output level, such as a spectrum analyzer.

The measurement principle is to set the relative velocity between the recording medium (41) and the magnetic head (42) as (V), set the switch (43) to the recording side, and measure the frequency (V) output from the oscillator (44) as shown in Figure 4. f) while changing the amplitude of the signal on the recording medium (41
) using a magnetic head (42). Then, switch the switch (43) to the playback side and insert the recording medium (43).
Perform playback of I). This playback output level is detected by a detector (
45) to obtain a characteristic curve as shown in FIG. 3(a). Here, the reason why the curve (a) has a peak is because a phase shift of magnetization occurs in the depth direction of the recording medium.

Furthermore, let the above relative velocity be (2■) and the frequency be (2f
), and by doing the same work as above, the third
Obtain a characteristic curve as shown in figure (b). Here, the recording wavelength (
λ) is λ=1,000−10F=constant and does not change. Therefore, only frequency-dependent changes in head efficiency appear.

In Figure 3, if the states of magnetization at the peak points of (a) and (b) are equal, the ratio (△i) of the two is 1, and the frequency (f) is (2
This is correlated with the change in print head efficiency caused by the change in f).

By measuring the above method at a large number of frequencies, the frequency characteristics of the recording head efficiency as shown in FIG. 7 can be obtained.

In addition to the measurement of recording efficiency using the two-speed modified method described above, measurement methods such as the conventional method have also been proposed.

This is the 1985 IEEE Transacfion
son Magnetics, Vol MAG-21
, NO, 4 “An Improved Measure
element of the Absolute
Efficiency of Magnetic
Heads by Saturating the G
ap Field", and this method will be explained based on FIG.

In Figure 5, (51) is a magnetic herad core, (52)
is an operating gap, (53) is a winding window, (54) is a main winding, and (55) is a secondary winding, and in the case of a normal head, there is no secondary winding (55).

The measurement method is to apply an excitation current to the main winding (54) and increase the current. The second volume of this time &! The state of the output voltage of (55) is shown in FIG. As the excitation current increases, the magnetic flux passing through the working gap increases, and the secondary winding (5
5) The induced voltage increases. However, the gap part (
52) has a narrow magnetic path, so it quickly becomes magnetically saturated (8 points),
If the excitation current is increased too much, the voltage induced in the secondary winding (55) will increase due to magnetic flux leakage to the outside.
The rate of increase decreases and an inflection point (S) appears. Let the excitation current at this time be (Is). Here, the recording head efficiency (rL) is the magnetic potential difference Hg, g
(Hg is the magnetic field in the gap, g is the gap length), so. Here, (BS) is the saturation magnetic flux density of the het core material. (Is) determined by this formula (1)
Determine whether the record head efficiency fee). In this method, as shown in Fig. 7, by measuring a large number of frequencies,
Frequency characteristics of recording head efficiency can be obtained.

[Problem to be solved by the invention] Since the conventional magnetic head evaluation device is configured as described above, in the former two-speed modified method, not only must recording and reproduction be performed each time, but also recording and reproduction must be performed each time. It was necessary to attach the measuring mechanism and head to the measuring mechanism. Furthermore, even if the relative speed changes, it is necessary to ensure that there are no mechanical changes, such as changes in the spacing between the recording medium and the head, making it difficult to perform accurate measurements.

In addition, in the latter measurement method, it is necessary to apply a secondary winding to the head core, and considering that actual heads are designed to make the winding window as small as possible in order to improve efficiency, it is necessary to apply a secondary winding to the head core. In addition to requiring a lot of effort to wind the wire,
Unless the area, shape, and position of the closed circuit formed by the secondary winding are appropriate, there are problems such as the inflection point shown in Figure 6 being difficult to find and accurate measurement impossible.

This invention was made to solve the above-mentioned problems, and it is possible to accurately measure recording efficiency with a simple configuration that does not require recording and reproducing each time, and does not require any special mechanical parts or secondary windings. The purpose of the present invention is to provide a magnetic head evaluation device that can perform the following steps.

[Means for Solving the Problems] The magnetic head evaluation device according to the present invention reduces the inductance value caused by magnetic saturation of the magnetic head when changing the oscillation amplitude of the oscillator connected to both ends of the coil of the magnetic head. The method is characterized in that the magnetic saturation current of the head is determined from the point, and the zero recording efficiency of the magnetic head is measured from this.

[Operation] According to the present invention, the magnetic saturation current of the magnetic head is determined by measuring the change in the inductance value of the magnetic head due to the change in the oscillation amplitude of the oscillator, and the magnetic saturation current of the magnetic head is determined based on this magnetic saturation current and the saturation magnetic flux density of the head core material. To measure the recording efficiency of

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the basic configuration of a magnetic head evaluation device according to an embodiment of the present invention.

In the figure, (11) is an oscillator, and a magnetic head (14) is an oscillator.
) is connected to both ends of the coil (15), and both its amplitude and frequency are variable. (12) is a voltmeter that can measure amplitude and phase; (13) is an ammeter that can measure amplitude and phase; (10) is the oscillator (11), voltmeter (12),
This is an inductance measuring instrument consisting of an ammeter (13).

Next, the measurement principle of the above configuration will be explained.

The output of the oscillator (11) is transmitted to the coil (
15). At this time, the current flowing through the coil (15) and the voltage across the coil are measured using an ammeter (13).
The inductance of the magnetic head (14) is determined by measuring with a voltmeter (12) and a voltmeter (12).

The oscillator (ll) has a variable amplitude, and when the amplitude is changed from small to large, the head (14)
It can be seen that the inductance decreases from a certain current value due to magnetic saturation. If the current value at this point is (Is), then as explained in the conventional example, the recording efficiency ('l,)
teeth.

determined by

Furthermore, the oscillator (11) has a variable frequency, and by varying one frequency and determining the recording efficiency in the same manner as above, the saturation current value varies depending on the frequency, and the frequency characteristics of the recording efficiency as shown in Fig. 7 are obtained. can get.

In the above embodiment, the frequency of the oscillator (11) is variable, but the frequency may be fixed. In this case, the effect is that the recording efficiency of a large number of magnetic heads can be determined in a short time when evaluating them. has.

[Effects of the Invention] As described above, according to the present invention, the saturation current is determined by measuring inductance, and the recording efficiency of the magnetic head is obtained. It is no longer necessary to attach it to the
Since there is no need for a secondary winding, the overall configuration is simplified, and recording efficiency can be easily and efficiently measured. Also.

There is no need to add any processing to the magnetic head, and recording efficiency can be measured simply by measuring inductance, so it can be very effectively applied to selecting good quality heads from mass-produced heads.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a magnetic head evaluation device according to an embodiment of the present invention, FIG. 2 is a graph showing the measurement principle of the present invention, and FIG. 3 is a graph showing the conventional measurement principle.
Figure 4 is a block diagram showing the configuration of a conventional magnetic head evaluation device, Figure 5 is a configuration diagram of another conventional example, Figure 6 is a graph showing the measurement principle of another conventional example, and Figure 7 is recording efficiency. 3 is a graph showing the frequency characteristics of . (10)--Inductance measuring device, (11)--
Oscillator, (12)--voltmeter, (13)-- ammeter, (14)--magnetic head, (41)-- magnetic recording medium. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A means for measuring the inductance of the magnetic head by exciting an oscillator connected to both ends of the coil of the magnetic head, a means for changing the oscillation amplitude of the oscillator, and a point at which the inductance value of the magnetic head starts to decrease. A magnetic head evaluation device comprising means for calculating a magnetomotive force from a current flowing through a coil and determining recording efficiency of a magnetic head from a saturation magnetic flux density of a head core material. (2) The magnetic head evaluation device according to claim 1, wherein the oscillation frequency and oscillation amplitude of the oscillator are variable.