JPS6334990B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic field detection device that aims to reduce noise and errors caused by electromagnetic induction between an external magnetic field and a lead-out conductor portion from a magnetoresistive element made of a ferromagnetic thin film to a measuring instrument.

A magnetoresistive element made of a ferromagnetic thin film has two
There are terminal type, three terminal type, and bridge type methods, and the lead wires are composed of two, three, or more. However, in any configuration, the two minimum unit wires that make up an electrical circuit always form a loop.
There was a problem in that electromagnetic induction noise was generated due to the amount of linkage with an alternating magnetic field outside the area to be measured (or detected). In order to eliminate this electromagnetic induction noise, two wires are twisted alternately, and the alternating magnetic field that passes through many loops obtained by projecting the twisted state is in the opposite direction for each loop, so the entire wire is electromagnetic. Methods of canceling induced noise have been widely used as conventional techniques.

However, with the recent development of electronics technology, etched printed circuits and flexible tapes have come to be used for wiring. Since such circuits cannot alternately twist the wires, it has become difficult to eliminate induced noise by the conventional technique of twisting wires. Furthermore, if a ferromagnetic material used in the magnetoresistive element is, for example, a Ni--Co alloy, the rate of change in resistance due to a magnetic field can be increased. However, this significantly increases the cost of raw materials, so we are often forced to use commonly used permalloy materials.
Since the magnetic field detection output becomes small, countermeasures against electromagnetic induction noise are particularly important in such cases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic field detection device that suppresses electromagnetic induction noise caused by an alternating magnetic field other than the object to be measured in an extremely simple and inexpensive manner.

In order to achieve the above object, in the present invention,
One of the lead-out conductors from the magnetoresistive element to the measuring instrument is divided into two and placed with the other conductor in between, and the two loops are surrounded by one of the two conductors with the other conductor as the border. The areas were made equal.

FIG. 1 is a diagram explaining the principle of the present invention. In the figure, 1
1a is a magnetoresistive element, 1a is an element substrate, 2 and 3 are detection parts made of ferromagnetic thin films, 4, 5 and 6 are first, second and third terminals, respectively, and 7, 8 and 9 are first and second terminals, respectively. , 3 conducting wires, and 10 is a connection portion of both the second and third conducting wires. Now, if only the first conducting wire 7 is connected to the first terminal 4 and the second conducting wire 8 is connected to the second terminal 5, noise due to electromagnetic induction will occur when the loop made by these conducting wires interlinks with the external alternating magnetic field. arise. Therefore, in the present invention, a third terminal 6 is provided, which is directly connected to the second terminal 5, and a third conducting wire 9 is connected to the third terminal 6.
The loop formed by the first and second conductive wires and the loop formed by the first and third conductive wires are arranged so that their respective areas are equal. Like this 3
When an external alternating magnetic field passes through two loops formed by a real conductor, electromagnetic induction noise is excited in the two loops. The noise excited in this way is 2
The two loops have the same electromotive force, and they cancel each other out, eliminating noise. When using flexible coated conductor wires for the wiring from the first, second, and third terminals 4, 5, and 6, these three wirings are connected to each other as shown in Figure 2 of the embodiment of the present application, which will be described in detail later. Even if the two loops are twisted, the area of the two loops is the same, so the effect of the present invention is achieved. It's not something you can do.

FIG. 2 shows one embodiment of the present invention, in which three conductive wires are connected and twisted together in accordance with the principles of the invention disclosed in FIG. As a result of the twisting, the mutual spacing between the lines can be maintained constant.2
This has the effect of making the areas of the regions equal. Furthermore, if two conductive wires are twisted together when they cross a magnetic field in a specific direction, the direction of the magnetic field with respect to the wire will partially be in the opposite direction, so the entire twisted wire will generate a current due to the electromagnetic induction effect. It is a well-known fact that it becomes so small that it is difficult to detect. In the case of the embodiment shown in FIG. 2, this phenomenon acts in addition to the effect of making the areas of the two regions equal as described above, so that the noise reduction effect becomes more pronounced.

Furthermore, in this application, it has been described that the wiring of the simplest two-terminal detection element is wired using three wires.
As for the terminal type or bridge type, the basic circuit consists of two wires, so one of these
By reducing the number of books to two, this application can be easily adapted.

That is, this will be explained with reference to an embodiment shown in the drawings. FIG. 3 shows another embodiment in which the present invention is applied to a bridge type magnetic field detection device. R1,R
The magnetic field detection parts 2, R3, and R4 are arranged and connected in a bridge shape, and the output terminals are R4 to R5 and R6.
~ It is pulled out from the middle part of R7. Regarding this leader line, one line 7 is 1 as shown in FIG.
Pull it out as a book, and the other line is in two states 8, 9
The object of the present invention can be easily achieved by drawing out the following. In addition, the drawer lead wire 7 in Fig. 3,
If 8 and 9 are twisted together as shown in FIG. 2, a greater effect can be obtained.

As explained above, according to the present invention, even circuits in which lead wires are twisted and used, and even circuits in which it is difficult to eliminate induced noise by twisting conductor wires, such as printed wiring or flexible wiring, can be connected to an external alternating box. Induction noise caused by magnetic fields can be efficiently eliminated.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2 is a diagram showing one embodiment of the invention, and FIG. 3 is a circuit diagram showing another embodiment of the invention. 1... Element, 2, 3... Detection section, 4, 5, 6 are the first, second, and third terminals, respectively, 7, 8, and 9 are the first, second, and third conductive wires, respectively, and 10... Connection section.

Claims (1)

[Claims] 1. In a magnetic field detection device using a magnetoresistive element made of a ferromagnetic thin film, the magnetoresistive element has two terminals that are electrically connected in common and one terminal that is electrically independent from these terminals. Each of these terminals is connected to a lead wire leading to the measuring instrument, and the area of the area surrounded by the two lead wires connected to the common terminal is the area of the area connected to the independent terminal. A magnetic field detection device characterized in that each of the lead lines is arranged so as to divide the lead lines into equal parts.