JPS63218884A - Magnetic field sensor - Google Patents

Abstract

PURPOSE:To improve linearity and a temperature characteristics and thereby to improve accuracy in detection, by winding a coil for negative feedback on a magnetic core and thereby forming a negative feedback loop which supplies a part of an output of a processing circuit to said coil for negative feedback. CONSTITUTION:Sensor elements 1A and 1B are formed by winding coils 3A, 3B, 6A, 6B for detecting a magnetic field and coils 4A, 4B, 5A, 5B respectively on the opposite ends of magnetic cores AF1 and AF2 each of which uses three zero-magnetostrictive amorphous wires, which form a magnetic core having a length of 20-30mm and high permeability, for instance. In a geomagnetic azimuth sensor constructed in this way, the sensor elements 1A and 1B are driven with oscillation frequencies set by processing circuits 2A and 2B, respectively, and a difference between the intensities of magnetic fields generated in the respective coils 3A and 6A and 3B and 6B of the sensor elements 1A and 1B is taken out in the processing circuits 2A and 2B and outputted therefrom as analog outputs EOUT1, EONF1, EOUT2, EONF2. By applying negative feedback in this way, linearlity and a temperature characteristic are improved conspicuously.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a desired sensor output by processing the output of a sensor section, which is formed by winding a magnetic field detection coil around a magnetic core, in a processing circuit. The present invention relates to a magnetic field sensor that obtains the following characteristics.

(Prior Art) An example of a magnetic field sensor is a geomagnetic orientation sensor that measures weak geomagnetism to detect position and orientation.

As a conventional geomagnetic azimuth sensor, one shown in FIG. 6 is known. As shown in the figure, a drive coil Go is wound around a ring method magnetic core made of, for example, permalloy, and an X-direction detection coil C× and a Y-direction detection coil CY are wound on top of it to cross each other. The detection unit is DET, and the signal from the oscillator is input to the drive coil Go.
Each detection coil Cx based on the horizontal component of the earth's magnetism at that time
.

The signals obtained in CY are filtered, AC amplifiers,
Analog output EX, E via synchronous rectifier and DC amplifier
I am trying to get it as Y. Note that synchronization is achieved by inputting the output from the oscillator to a synchronous rectifier via a frequency multiplier circuit and a phase variable circuit.

As described above, analog outputs E@ corresponding to each azimuth θ as shown in FIG. 7 can be obtained, and the azimuth can be detected by this. In Figure 7, Ex is S
The in curve is shown, and EY is the COS curve.

However, in the device with the above configuration, since a ring-shaped magnetic core made of permalloy is used, the detection part DET
The ring core is large in size (for example, the diameter is 20 to 30 m and the thickness is 5 to 10 m), and since a plurality of windings must be applied to the ring core, it takes time to assemble. In addition, since permalloy is used, it is susceptible to photography and shock, and furthermore, the secondary side induced voltage based on the frequency (for example, 500 to 2 kllz) applied to the drive coil, which is the 1 o'clock side winding, is extracted as the X-axis output and Y-axis output. Because of this structure, the driving frequency was low and stability was lacking, and there was a problem in that the drift was especially large.

Therefore, as shown in FIG. 8, the applicant of the present application developed a wire-shaped high permeability magnetic core AF1. AF2, detection units 1A and 1B in which a pair of coils facing the X-axis direction and a pair of coils facing the Y-axis direction in orthogonal coordinates are wound around the magnetic core at a predetermined interval, respectively, and coils in each axis direction. It consists of processing circuits 2A and 2B that respectively process the signals obtained from the
Earth's magnetism is detected by the detection units 1A and 1B, and output E obtained from each processing circuit 2A and 2B at this time. 1. We have proposed a geomagnetic orientation sensor that detects orientation based on Eo2 (Japanese Patent Application No. 6O-056586), aiming to solve the above problems.

(Problems to be Solved by the Invention) However, the above-mentioned geomagnetic direction sensor is smaller and lighter than the one shown in FIG. Although this method has high reliability, it is still insufficient particularly in terms of linearity and temperature characteristics, creating a need for improvement. It goes without saying that linearity and temperature characteristics are extremely important not only for geomagnetic azimuth sensors but also for magnetic field sensors in general in order to improve detection accuracy.

The present invention was made in view of the above circumstances, and an object thereof is to provide a magnetic field sensor with improved detection accuracy by improving linearity and temperature characteristics.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a method of winding a magnetic field detection coil around a magnetic core and processing the detection output of the magnetic field detection coil in a processing circuit to obtain a desired sensor output. In the sensor, a negative feedback coil is wound around the magnetic core, and a negative feedback loop is formed to supply a part of the output of the processing circuit to the negative feedback coil.

(Function) By supplying a part of the output of the processing circuit to the negative feedback coil and applying negative feedback, the linearity and temperature characteristics are improved.

(Example) The present invention will be specifically explained below using Examples.

Here, a case will be described in which the present invention is applied to a geomagnetic azimuth sensor as an example of a magnetic field sensor.

FIG. 1 is a schematic diagram showing an embodiment of the present invention, which includes two sensor sections 1A and 1B arranged intersectingly in the X and Y axis directions with respect to a horizontal plane, and from each sensor section IA and 1B. The obtained signals are processed and outputs in the X direction EOtlT 1 , EON
It is comprised of processing circuits 2A and 2B that obtain F1 and Y-direction outputs EOtlT2-EONF2, respectively.

Each of the sensor sections 1A and 1B has, for example, 20 to 3
Magnetic core AFt, AF using three zero magnetostriction amorphous wires (composition: CO66F e 4 S! 13815 at%, 110 μm type), which are 0mm long high magnetic permeability magnetic cores.
Magnetic field detection coils 3A, 3B, and 6A are installed at both ends of 2.

6B, and 1B output coil formed by winding negative feedback coils 4A, 4B, 5A, and 5B. For example, the number of turns of each coil is 200.
It is a turn, and the thickness of the wound coil is about 1#. And each coil 3A, 4A, 5
Processing circuit 2A corresponding to coil terminals A, 6A and 38.48° 58.68.

Connected to 2B.

Note that the configuration of each of the detection units is not necessarily limited to the case where an equivalent 21a core is used; for example, as shown in FIG. The X-axis sensor section is constructed by arranging a coil 4A wound around the end of the amorphous wire 10B and a magnetic field detection coil 6A wound around the end of the amorphous wire 10B in parallel so that the coils 3A and 6A are oriented in opposite directions. Similarly, coils 38.4B and 58.68 may be provided at each end of the two amorphous wires 10G and 10D, and these may be arranged in parallel to form the Y-axis sensor section.

Since both the processing circuits 2A and 2B have the same structure, the structure of one of the processing circuits 2A is shown in FIG. 2 as a specific example.

A lead wire J21. drawn out from the magnetic field detection coil 3A6A constituting the sensor section 1A. I! 2 are transistors Tr1. It is connected to the input end of the filter circuit 11 via Tr2 and signal line J23.14. At the base of each transistor Tr1, Tr2, each signal line A1.
A DC circuit connected to I2 (capacitor CB, resistor Re
) are applied in a crossed manner. Additionally, an additional resistor RL is connected between the signal lines J'3 and J'14.
RL are connected in series, and a variable resistor VR is connected in parallel with the slider of the variable resistor VR and the resistor RL.

The series connection point of RL is commonly grounded. Further, a power supply voltage E (positive electrode side) is applied to the other ends of the detection coils 3A and 6a, and an output pressure of 0°/1 can be taken out from the filter circuit 11. That is, the processing of this circuit is configured as a multivibrator bridge using two equivalent magnetic cores. The filter circuit 11 is a simple one consisting of resistors R1, R4 and capacitors C1, C2.

The output of the filter circuit 11 is then taken into a differential amplifier circuit 12 arranged at a subsequent stage. This differential amplifier circuit 12 has an inverting input terminal (
-), resistors R5 and Re are connected to the non-inverting input terminal (+), the other end of resistor R3 is connected to the output terminal of operational amplifier 13, and the other end of resistor R6 is grounded. The gain can be adjusted by changing the values of the resistors R2, Rs or R3, Re.

Output E of this differential amplifier circuit 12. A portion of NF 1 is supplied to the negative hall coils 4A and 5A via the negative feedback path 14. That is, the negative feedback path 14 is
A negative feedback resistor Rf is connected to the output end of the operational amplifier 13, a negative feedback coil 4A is connected to the other end of this resistor Rf, and one end of the unknown opening coil 5A is connected to the other end of the coil 4A. , is formed by grounding the other end of the coil 5A.

Note that the amount of negative feedback can be adjusted by changing the value of the negative feedback resistor Rf.

The geomagnetic azimuth sensor configured as described above includes a processing circuit 2A,
Drive frequency set in 2B (for example 100 to 500
) 12) for each sen + j part IA.

1B is driven, and each sensor section 1A at this time.

The difference in magnetic field strength generated between each coil 3A and 6A, 3B and 6B of 1B is taken out by each processing circuit 2A, 2B, and an analog output EO (IT 1 , EONF 1 and E
2. EoN "Output as 2.

tlT Next, test results of this geomagnetic direction sensor will be explained.

FIG. 3 shows analog outputs measured with respect to magnetic field strength with and without negative feedback.

The state without negative feedback is the state in which the negative feedback resistor Rf is removed, and the result is the same as the configuration shown in FIG. 8. In this state, E. ol is measured, and on the other hand, E in the case of negative feedback. N, is being measured. The ambient temperature of the sensor part was kept constant at 30° C. and 200° C. with and without negative feedback, respectively.

In addition, the current is 100 mA, the number of turns of each coil is 200 turns, the gain of the differential amplifier circuit 12 is 50 times, and the negative feedback resistor R
The value of f is 500Ω.

As is clear from FIG. 3, by applying negative feedback, the linearity and temperature characteristics are significantly improved. Therefore, the detection accuracy in a state where negative feedback is applied is dramatically improved compared to a state where negative feedback is not applied.

As a result of measuring geomagnetism using the geomagnetic azimuth sensor configured as described above, the relationship between the analog output obtained from each processing circuit and the azimuth angle is as shown in FIG.

The present invention is not limited to the above-mentioned embodiments, and various modifications are possible. For example, in the embodiments described above, a geomagnetic direction sensor has been described, but the present invention can also be applied to other magnetic field sensors.

Further, in the embodiment described above, a magnetic field detection coil and a negative feedback coil are provided at both ends of the magnetic core to form the sensor section 1A.

1B is shown, but the sensor part IA is not limited to this, and as shown in FIG. 9, a magnetic field detection coil and a negative feedback coil are provided only at one end of the magnetic core.

Even in the case of configuring 1B, the same effect as described above can be obtained.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide a magnetic field sensor with improved detection accuracy by improving linearity and temperature characteristics.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of one embodiment of the present invention, Fig. 2 is a circuit diagram showing an example of its processing circuit, Fig. 3 is a characteristic diagram showing the effects of the present invention, and Fig. 4 is a measurement of the present embodiment. Characteristic diagram showing the results,
Fig. 5 is a schematic diagram showing the other side of the present invention, Fig. 6 is a schematic diagram of the conventional device, Fig. 7 is a characteristic diagram showing the measurement results, and Fig. 8 is the geomagnetic direction proposed earlier by the applicant. FIG. 9 is a schematic diagram of a sensor showing another embodiment of the present invention. 1A, IB...Sensor section, 2A, 2B...Processing circuit, 3A, 3B, 6A, 6B...Magnetic field detection coil, 4A
, 4B, 5A, 5B... Negative return coil, 14...
Negative feedback path, AFL, AF2...magnetic core. Fig.3

Claims (4)

[Claims] (1) In a magnetic field sensor in which a magnetic field detection coil is wound around a magnetic core and the detection output of this magnetic field detection coil is processed by a processing circuit, a negative feedback coil is installed near the magnetic field detection coil wound around the magnetic core. A magnetic field characterized in that a first sensor section and a second sensor section are arranged in an intersecting manner, and a negative feedback path supplies a part of the output of the processing circuit to the negative feedback coil. sensor. (2) The magnetic field sensor according to claim 1, wherein each sensor section is provided with a magnetic field detection coil and a negative feedback coil at one end of one magnetic core. (3) The magnetic field sensor according to claim 1, wherein each sensor section is provided with a magnetic field detection coil and a negative feedback coil at both ends of one magnetic core. (4) The magnetic field sensor according to claim 1, wherein the magnetic cores of each sensor section are equivalent two magnetic cores.