JPH01291180A - Magnetism detecting device - Google Patents

Abstract

PURPOSE:To obtain a measured value corresponding to the polarity by allowing an AC or DC magnetic field to work on a magneto-resistance element by a loop circuit. CONSTITUTION:On a non-magnetic insulating substrate 1, a magneto-resistance element 2 consisting of a film-like ceramic electromotive conductor is formed. Also, on the substrate 1, a loop line 3 is formed by an integral construction with the element 2 by a printing technique, and an excitation power source 4 for allowing a current to flow to the loop line 3 and generating a magnetic field is provided. In this state, by the loop line 3, the magnetic field is generated so as to work on the element 2, and a resistance of the element 2 at the time when a magnetic field to be measured and the magnetic field which has been generated by the loop line 3 have worked simultaneously on the element 2 is detected by a detecting part. Accordingly, by generating a suitable magnetic field by the loop line 3, the polarity of the magnetic field to be measured can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a magnetic detection device capable of measuring weak magnetic fields due to biomagnetism, terrestrial magnetism, etc. using a magnetoresistive element made of a superconducting material.

<Prior Art> Conventionally, as such a magnetic detection device, there is one shown in FIG. This magnetic detection device is installed at both ends of a magnetoresistive element 5I made of a superconducting material manufactured by silk screen or spraying on a non-magnetic insulating substrate (not shown in the figure) such as an alumina plate. current electrode 52a.

The voltage electrode 53a is formed by passing a current on the order of microamperes to milliamperes through the voltage electrode 52b and measuring the voltage between the voltage electrodes 53a and 53b provided inside the current electrodes 52a and 52b.

The resistance R of the magnetoresistive element 51 between the magnetoresistive elements 53b and 53b is measured.

The resistance R changes depending on the magnetic field B acting on the magnetoresistive element 51, and the change in resistance R with respect to the magnetic field B when the current is constant is as shown in FIG.

Therefore, by measuring this resistance R, the magnetic field can be measured.

<Problems to be Solved by the Invention> By the way, there is a magnetic gap in the vertical direction of the substrate of the magnetoresistive element 51, and the magnetic field B acting on the magnetoresistive element 51 due to the magnetic gap is shown in FIG. 7(A). When the resistance R changes over time as shown in FIG. 7(C), the resistance R becomes as shown in FIG. 7(C). Next, under similar circumstances, when a magnetic field B as shown in FIG. 7(B) is applied, the resistance R becomes as shown in FIG. 7(C). That is, in the conventional magnetic detection device described above,
Even if magnetic fields with different polarities as shown in FIGS.
As shown in Figure (C), there is a problem in that the difference in the polarity of the magnetic field cannot be detected. This becomes a big problem, for example, when medical diagnosis is performed using a weak magnetic field generated by magnetocardiography or the like.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic detection device capable of detecting a difference in polarity of a weak magnetic field using a magnetoresistive element made of a superconducting material.

Means for Solving the Problems> In order to achieve the above object, the first invention measures a magnetic field by having a magnetoresistive element made of a superconducting material and a detection section that detects the resistance of the magnetoresistive element. The magnetic detection device is characterized in that it includes a loop circuit that generates a magnetic field so as to act on the magnetoresistive element.

Further, a second invention provides a magnetic detection device that measures a magnetic field by having a magnetoresistive element made of a superconducting material and a detection section that detects the resistance of the magnetoresistive element, which has a frequency sufficiently higher than the frequency of the magnetic field to be measured. an AC power source that generates a voltage at a certain frequency; a loop circuit that is connected to the AC power source and generates an AC magnetic field having the same frequency as the frequency of the AC power source so as to act on the magnetoresistive element; a magnetic field to be measured; and the loop circuit. a first increase/decrease detection circuit that detects an increase/decrease in the detected value detected by the detection section when an alternating current magnetic field generated by the circuit simultaneously acts on the magnetic resistance element; a second increase/decrease detection circuit for detecting; a determination circuit for receiving the output of the first increase/decrease detection circuit and the output of the second increase/decrease detection circuit and determining whether or not the two outputs have the same polarity; When the discrimination circuit determines that both outputs have the same polarity, the detection value detected by the detection section is output as is, and when the discrimination circuit determines that both outputs do not have the same polarity. a selection inversion circuit that inverts the positive/negative of the detection value detected by the detection section and outputs it; and a low-pass filter that removes a component of the same frequency as the frequency of the alternating current magnetic field from the detection value output by the selection inversion circuit. It is characterized by having the following.

Further, a third invention is a magnetic detection device that measures a magnetic field by having a magnetoresistive element made of a superconducting material and a detection section that detects the resistance of the magnetoresistive element, in which a magnetic field is applied to the magnetoresistive element. and a DC power source that generates a DC magnetic field in the loop circuit, and when the magnetic field to be measured and the DC magnetic field simultaneously act on the magnetic resistance element, the resistance value of the magnetic resistance element is It is characterized in that the resistance value is greater than the minimum resistance value of the magnetoresistive element.

In the first invention, the loop circuit generates a magnetic field to act on the magnetoresistive element, and when the magnetic field to be measured and the magnetic field generated by the loop circuit simultaneously act on the magnetoresistive element, A detection unit detects the resistance of the resistance element.

Therefore, the polarity of the magnetic field to be measured can be detected by generating an appropriate magnetic field in the loop circuit.

Further, in the second invention, the AC power source generates a voltage with a frequency sufficiently higher than the frequency of the magnetic field to be measured, and the loop circuit connected to the AC power source generates an AC magnetic field having the same frequency as the frequency of the AC power source. is generated so as to act on the magnetoresistive element. The first increase/decrease detection circuit detects an increase or decrease in the detection value detected by the detection unit when the magnetic field to be measured and the AC magnetic field generated by the loop circuit simultaneously act on the magnetic resistance element, while the AC power source A second increase/decrease detection circuit detects an increase/decrease in voltage. Then, a discrimination circuit receives the output of the first increase/decrease detection circuit and the output of the second increase/decrease detection circuit, and discriminates whether or not these two outputs have the same polarity. When it determines that both of the outputs have the same polarity, it outputs the detection value detected by the detection section as is, and the determination circuit outputs the detected value as it is.
When it is determined that the two outputs do not have the same polarity, the detection value detected by the detection section is output with its sign reversed. Next, a low-pass filter removes a component of the same frequency as the frequency of the alternating magnetic field from the detected value outputted by the selection inversion circuit.

In this way, it is possible to determine whether the polarity of the increase or decrease in the detected value detected by the detection unit when the magnetic field to be measured and the alternating magnetic field act simultaneously on the magnetoresistive element is the same as or different from the polarity of the increase or decrease in the voltage for generating the alternating magnetic field. When the polarities are the same, the detected value is output as is, and when the polarities are different, the detected value is output with its sign reversed, so it is possible to measure the polarity according to the polarity of the magnetic field being measured. value can be obtained.

Further, in the third invention, when the magnetic field to be measured and the DC magnetic field from the loop circuit simultaneously act on the magnetic field resistance element, the resistance value of the magnetic resistance element is larger than the minimum resistance value of the magnetic resistance element. A DC magnetic field is generated in the loop circuit so that Therefore, by detecting the polarity of the difference between the resistance value of the magnetoresistive element and the resistance value to the DC magnetic field, the polarity of the magnetic field to be measured can be determined.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 is a schematic diagram of the main parts in an embodiment of the present invention.

In FIG. 1, ■ is a non-magnetic insulating substrate, 2 is a magnetoresistive element made of a film-like ceramic superconductor formed on a bipedal substrate L, and 3 is a magnetoresistive element formed on the substrate I by printing technology. A loop wire 2 is integrally formed with the loop wire, and 4 is an excitation power source for causing a current to flow through the loop wire to generate a magnetic field.

FIG. 2 shows an example of a measuring circuit of a magnetic detection device in which the excitation power source 4 is an AC power source, generates an AC magnetic field in the loop wire 3, and measures the magnetic field to be measured together with its polarity. FIG. 3 shows the waveforms of the magnetic field and the waveforms at various parts of the circuit to explain the operation of the circuit.

FIG. 3(A) shows the waveform of the magnetic field to be measured.

The polarity of this magnetic field to be measured differs depending on the time, similar to the magnetic field to be measured shown in FIG. 7(B) in the conventional example. Further, FIG. 3 (13) shows the alternating current magnetic field generated by the loop wire 3. Although this alternating magnetic field is drawn at a lower frequency than the actual frequency in the diagram for ease of understanding, it is a sine wave with a frequency sufficiently larger than the frequency of the magnetic field to be measured shown in Figure 3 (A) above. It is a minute reference magnetic field of waves.

The instantaneous value of this alternating magnetic field is expressed as S=Sm sin ωt, where Sm is the amplitude and ω is the angular frequency.

Here, the amplitude Sm may be equal to or smaller than the amplitude of the magnetic field to be measured. Also, the angular frequency ω needs to be sufficiently large compared to the angular frequency of the magnetic field to be measured, but it is not preferable to increase it unnecessarily because the signal will be processed later. In the case of a biomagnetic field, it is on the order of KHz.

When the AC magnetic field shown in FIG. 3(B) is added to the magnetic field to be measured shown in FIG. 3(A) above, a magnetic field having a waveform shown in FIG. 3(C) is obtained. Then, a detection section (not shown) connected to the magnetoresistive element 2 detects a change in resistance of the magnetoresistive element 2 when this composite magnetic field acts on the magnetoresistive element 2 shown in FIG. Since the characteristics of the magnetoresistive element 2 are as shown in FIG. 6, the detection value of the detection section is as shown in FIG.
) The signal voltage will be as shown below. That is, the time t when the magnetic field to be measured (A) is in the positive region. 3rd between Ll and
It shows the same characteristics as the composite magnetic field shown in Figure (C), but at time 1 when the magnetic field to be measured (A) is in the zero region. Between 1 and 2, it exhibits a characteristic similar to full-wave rectification as shown in the figure, and after 2 hours, it exhibits an inversion characteristic with respect to the composite magnetic field shown in FIG. 3(c).

Here, by comparing the waveforms in FIG. 3(B) and the waveforms in FIG. 3(D), in areas where the directions of increase and decrease of both waveforms are the same,
If the value (V, ) in Figure 3(D) is left as is, and the polarity of VI is reversed in regions where the directions of increase and decrease are different, Figure 3(C)
) can be obtained with the same characteristics as shown in ().

Therefore, the voltage for generating the reference magnetic field shown in FIG. 3(B) is differentiated by the differentiating circuit 21 shown in FIG.
) is detected by the bypass filter (HP) shown in Figure 2.
F) After removing low frequency components in step 22, differentiation is performed in a differentiating circuit 23. The output of the differentiating circuit 21 is shown in FIG. 3 (G), and the output of the differentiating circuit 23 is shown in FIG. 3 (E). The above website
F'22 is not necessarily necessary when there is little temporal change in the magnetic field to be measured. Next, the output of the differentiating circuit 21 (
When the output (E) of the differential circuit 23 and the output (E) of the differentiating circuit 23 are respectively binarized by the binarization circuits 24 and 25 with the positive part set to "High" and the negative part set to "Low", the results are shown in Fig. 3 (H) and The output shown in FIG. 3(F) is obtained. 2@ conversion circuit 24.2
The outputs (H) and (F) of 5 are checked for consistency by a comparison circuit 26, and the signal shown in FIG. 3 (I) is obtained. This comparison circuit 26 is a commonly used exclusive OR It is a gate, and is designed to output "High" when the binarized outputs (F) and (H) match, and output "Low" when they do not match.

The output (1) of the comparison circuit 26 is input to the selection inversion circuit 27. This selection inversion circuit 27 receives this output (1) and the detection value (D), and the output (1) becomes "l(high)".
”, the detected value (D) is output as is, and output (1)
When is "Low", the detected value (D) is output with its polarity inverted. Therefore, the output waveform of the selection inversion circuit 27 is
The waveform becomes as shown in Figure (J), and this waveform is the same as the waveform of the composite magnetic field shown in Figure 3 (C). When this output (J) is passed through a low-pass filter (LPF) 28 that removes frequency components having the same frequency as the AC reference magnetic field, an output having the same waveform as the measured magnetic field shown in FIG. 3(A) is obtained.

FIG. 4 explains the operation of a magnetic detection device in which the excitation power source 4 shown in FIG. 1 is a DC power source and generates a DC magnetic field in the loop wire 3.

This magnetic detection device applies a DC bias magnetic field B to the loop line 3.

This bias magnetic field B is used to generate an operating point due to the magnetic field to be measured as shown in Fig. 3 (A). Shift by
The resistance value of the magnetoresistive element 2 is made higher than its lowest resistance point.

By subtracting the DC magnetic field from the measured value thus obtained, a measured value corresponding to the polarity of the magnetic field to be measured can be obtained.

This magnetic detection device is for use in a separate part of the device, compared to the above-mentioned magnetic detection device that generates an alternating magnetic field, and although its operating range is narrower and the reality is slightly lower, it is more applicable to practical equipment.

In this way, by flowing an alternating current or direct current through the loop wire and causing the alternating current or direct current magnetic field to act on the magnetoresistive element 2 in addition to the magnetic field to be measured, it is possible to obtain a measured value according to the polarity of the magnetic field to be measured. can.

In the above embodiment, the loop line was created on the substrate by printing technology, but it may also be made of a wire, or the loop line may be formed on a separate substrate and that substrate brought close to the substrate I. You can leave it there.

In addition to the above-mentioned uses, this loop line can be used to flow a reference current through this loop line to check and correct the operation of the magnetoresistive element and the entire device. Furthermore, it is arranged so that the angle with respect to the magnetoresistive element is variable, and is used to confirm the direction of the magnetic field to be measured. It is also possible to confirm the direction of the magnetic field to be measured by arranging a plurality of loop lines at different angles and passing reference currents having a phase difference through each loop line.

<Effects of the Invention> As is clear from the above, the magnetic detection device of the present invention has the following effects:
Since the loop circuit causes an alternating current magnetic field or a direct current magnetic field to act on the magnetoresistive element, even if the polarity of the magnetic field to be measured changes, it is possible to obtain a measured value according to the polarity.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of the main parts in an embodiment of the present invention, Fig. 2 is a measurement circuit diagram for generating an alternating magnetic field in the loop wire in the above embodiment and measuring the magnetic field, and Fig. 3 is a diagram of the above embodiment. A waveform diagram for explaining the operation of the measurement circuit, Fig. 4 is an explanatory diagram of the operation when a DC magnetic field is generated in the loop wire in the above embodiment, Fig. 5 is a configuration diagram of the main part of the conventional example, and Fig. 6 7 is a diagram showing general characteristics of a magnetoresistive element made of a superconducting material, and FIG. 7 is a diagram showing an example of a magnetic field acting on the magnetoresistive element and measured values. ! ... Substrate, 2... Magnetoresistive element, 3... Loop wire, 4... Excitation power supply, 21.23... Differential circuit, 2
6... Comparison circuit, 27... Selection inversion circuit, 28...
・Low bass filter. Patent applicant: Sharp Corporation Agent
Patent attorney Aoyama Ao and one other person Figure 3 Figure 4 Figure 57 -8 u 8 Figure 7

Claims (3)

[Claims] (1) In a magnetic detection device that measures a magnetic field by having a magnetoresistive element made of a superconducting material and a detection section that detects the resistance of the magnetoresistive element, a loop is generated to cause a magnetic field to act on the magnetoresistive element. A magnetic detection device characterized by comprising a circuit. (2) In a magnetic detection device that measures a magnetic field by having a magnetoresistive element made of a superconducting material and a detection unit that detects the resistance of the magnetoresistive element, a voltage with a frequency sufficiently higher than the frequency of the magnetic field to be measured is generated. a loop circuit connected to the AC power source and generating an AC magnetic field having the same frequency as the frequency of the AC power source so as to act on the magnetoresistive element; and a magnetic field to be measured and an AC generated by the loop circuit. a first increase/decrease detection circuit that detects an increase/decrease in the detection value detected by the detection section when a magnetic field simultaneously acts on the magnetoresistive element; and a second increase/decrease detection circuit that detects an increase/decrease in the voltage generated by the AC power source. , a discrimination circuit that receives the output of the first increase/decrease detection circuit and the output of the second increase/decrease detection circuit and determines whether or not the two outputs have the same polarity; and the discrimination circuit determines whether the two outputs have the same polarity. When it is determined that the output has polarity, the detection unit outputs the detected value as it is, and when the determination circuit determines that the two outputs do not have the same polarity, the detection unit outputs the detection value detected by the detection unit. The present invention is characterized by comprising: a selection inversion circuit that inverts the sign of the detected value and outputs it; and a low-pass filter that removes a component of the same frequency as the frequency of the alternating current magnetic field from the detection value outputted by the selection inversion circuit. magnetic detection device. (3) In a magnetic detection device that measures a magnetic field by having a magnetoresistive element made of a superconducting material and a detection section that detects the resistance of the magnetoresistive element, a loop is generated to cause a magnetic field to act on the magnetoresistive element. circuit, and a DC power supply that generates a DC magnetic field in the loop circuit, and when the magnetic field to be measured and the DC magnetic field simultaneously act on the magnetic resistance element, the resistance value of the magnetic resistance element becomes the minimum value of the magnetic resistance element. A magnetic detection device characterized in that the resistance value is greater than the resistance value.