JPS5843682B2 - Whole head toy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic signal reading device using a Hall head.

Currently, optical or electromagnetic induction type position detection sensors are in practical use.

However, for example, in a coil type position detection sensor, which is a typical example of an electromagnetic induction type, such as a magnetic head, a magnetic medium, such as a magnetic tape whose north and south poles are magnetized at a predetermined interval, or a magnetic head, If the magnetic head is not run at a strictly constant speed, the output of the magnetic head will fluctuate sharply.
Accurate reading becomes difficult.

Also, it is impossible to read under extreme static conditions, ie direct current.

Therefore, stationary reading is possible, and it is possible to read from DC to several MHz.
Various reading devices using magnetoelectric transducers that can easily obtain flat characteristics have been developed.

However, the material characteristics of the magnetoelectric transducer, namely In
Due to the poor temperature characteristics peculiar to Sb and the like, there are many difficulties in putting a high-precision reading device into practical use.

For example, since the temperature coefficient of the material of the magnetoelectric conversion element exhibits a value of 2% or more, the output vp-p of the element varies depending on the temperature.

In addition, unbalanced voltage occurs due to the shape.

Figure 1 shows the element output yp- when one Hall element is used.
p is the unbalanced voltage V of the Hall element.

FIG.

As shown in the figure, the output vp-p changes, for example, as 'y,'P-P (7) when the temperature changes.

Unbalanced voltage ■. Even if Vth is constant with respect to temperature changes, for example, the operating potential Vth of the amplifier constituting the reading device
Assuming that is constant, the obtained output pulse has a pulse width T before the temperature changes, but after the temperature changes, the pulse width becomes T', causing a fluctuation in the reading position.

FIG. 2 shows the changes in the output vp-P of the Hall element and the unbalanced voltage ■o with respect to temperature.

■P-P〉〉■. In the case of , the error regarding the position of T7T is small, but vP p>V or VP-P≦■
In the case of o, the error regarding the position of T'/T becomes large and accurate position reading becomes impossible.

In this way, positions are generally read using Xerox points, but VP-P and V.

If both vary with temperature, even if the magnetoelectric transducer can be read stationary, it is not suitable for practical use.

In general, the output characteristics using a Hall element are R.H. VH=K・■・B=−・■・B(1) It can be expressed as in equation (1).

However, RH is Hol constant and d is Hol constant. is the magnetic flux density.

Proportional to flux density.

if, thickness of the element, ■ is the current, B Hall output vH is current and magnetic Considering the temperature coefficient in equation (1) It can be shown as follows.

However, α is the temperature coefficient of the Hall constant, and T is the temperature.

If the Hall element is driven at a constant voltage to eliminate the influence of the temperature coefficient α, the Hall output ■H becomes as shown by the following equation (2).

However, β is the temperature coefficient of the Hall element current-side internal resistance.

In equation (2), if the internal resistance of the Hall element current side is R0, then α and β are expressed as follows.

That is, it is possible to obtain an expression that is independent of temperature.

However, since α\β is actually the case, vp p
Lord V.

Alternatively, in the vicinity of Vp-P≦■o, the above formula (2) 7 cannot be applied.

Therefore, the drawbacks mentioned above still exist.

The present invention has been made to eliminate the above-mentioned drawbacks, and examples of the present invention will be described in detail below.

In the present invention, as shown in FIG. 3, two Hall elements H1 and H2 are arranged along the magnetic surface sM of the magnetic medium.
The Hall elements are arranged at a constant distance l shorter than one wavelength of the NS pole magnetized to M, and the Hall element is This makes it possible to ignore the temperature coefficient of , making highly accurate position reading possible.

The two Hall elements H1 and H2 are connected to II (
The fact that the temperature coefficient can be ignored by using the output difference between the pixel elements will be explained below.

Now, let us assume that the output of the first Hall element H1 is ■, and the output of the second Hall element H2 is VH2, and that the unbalanced voltage is also considered (assuming that the unbalanced voltage coefficient is H■0.H■2). Output ■H
1,■H2 becomes.

As is clear from this equation, if the two Hall elements are arranged as shown in FIG. 3 and the output difference of the pixel elements is obtained, the temperature function can be completely eliminated.

In the above, the magnetic surface sM of the magnetic medium and the Hall element H1,
The gap between H2 constantly changes due to the movement of the magnetic medium, so if the distance l between the two Hall elements H1 and H2 is longer than one wavelength of the NS pole of the magnetic signal, VH1\VH2
However, in the present invention, the distance is set within one wavelength of the magnetic signal as shown in FIG. The physical effects are the same, so VH2 is obtained approximately at ■H.

Further, as a specific circuit configuration for obtaining the output difference between two Hall elements, as shown in Fig. 4, Hall elements H1 and H2 arranged as shown in Fig. 3 are driven by a constant voltage DC power source Vo, and each element is The outputs VHt and VH2 of
After amplifying with 1 and A2, if both amplifier outputs VA1 and ■A2 are supplied to the subtracter As to calculate VA, -VA2, the subtracter As will output information that is completely unrelated to temperature changes. This results in a highly accurate reading output.

Next, this point will be explained with reference to the waveform diagram of FIG.

Outputs of amplifiers A1 and A2 in Fig. 4 ■A1 and vA
Since the corresponding Hall elements H1 and H2 are separated by a distance l shorter than one wavelength of the NS pole as shown in Fig. 3, they are equal and have a phase shift of a distance l as shown in Fig. 5a. This will be the output waveform.

In this case, it is assumed that the unbalanced voltages of both Hall elements are equal and ①o.

Also, the output waveform is based on ■. This is an indication for

Both outputs ■A1. When the difference in vA2 is taken, the waveform shown in FIG. 5 is obtained.

■ of this waveform ■A1-■A2.

If zero-crossing points are used, the distance T between the zero-crossing points will always be constant regardless of temperature changes, as shown in FIG. 5C.

In this way, according to the present invention, by using two Hall elements, the temperature coefficients of each element cancel each other out, so the temperature function can be completely ignored. Defects can be removed.

Furthermore, since the Hall element can be used while ignoring the temperature coefficient, there are many advantages such as improved position reading accuracy.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing the output voltage of one Hall element with its unbalanced voltage as a reference, and FIG. 2 is a temperature characteristic diagram showing changes in the output voltage and unbalanced voltage of the Hall element with respect to temperature.
FIG. 3 is an explanatory diagram showing the arrangement of two Hall elements used in the magnetic signal reading device according to the present invention, FIG. 4 is a schematic configuration diagram showing an example of the reading device according to the present invention, and FIG. FIG. 3 is a waveform diagram illustrating the operation of the reading device according to the invention. Explanations of the symbols representing the main parts of the figure are as follows. Hl, H2...Hall element, SM...
Magnetic surface, l... Distance between two Hall elements.

Claims (1)

[Claims] 1. Two Hall elements are placed along the magnetic surface of the magnetic medium at a distance shorter than one wavelength of the NS pole of the magnetic signal recorded on the magnetic surface, and the output of the difference between the outputs of both Hall elements is calculated. A magnetic signal reading device using a Hall head, characterized in that a temperature coefficient of the Hall element is removed from the read signal by obtaining the magnetic signal as a read signal.