JPH07301644A - Electromagnetic field sensor - Google Patents

Abstract

PURPOSE:To provide an electromagnetic field sensor usable in a wide temperature range without being influenced by the temperature. CONSTITUTION:An electromagnetic field sensor is provided with detecting parts A, B having polarizers 5, analyzers 7 and magnetooptical elements 6A, 6B, and detects a current or the magnetic field utilizing the Faraday effect of the magneto-optical elements 6A, 6B. Two detecting parts A, B are disposed in parallel, and one detecting part A has the magneto-optical element 6A with a flat temperature characteristic in a low temperature area, while the other detecting part B has the magneto-optical element 6B with a flat temperature characteristic in a high temperature area. This electromagnetic field sensor detects through the detecting part having the magneto-optical element with the flat temperature characteristic in the low temperature area in the case of measuring the current or magnetic field in the low temperature area, and detects through the detecting part having the magneto-optical element with the flat temperature characteristic in the high temperature area in the case of measuring the current or magnetic field in the high temperature area. A wide temperature area from the low temperature area to the high temperature area can be thereby measured without correcting the detection result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic field sensor for measuring a current and a magnetic field by utilizing the Faraday effect of a magneto-optical element having a magneto-optical effect.

[0002]

2. Description of the Related Art FIG. 7 is a schematic configuration diagram showing a conventional electromagnetic field sensor. In the figure, 1 is a light source, 2 is an input optical fiber, 3 is a collimator lens, 4 is a total reflection mirror, 5 is a polarizer, 6 is a magneto-optical element, 7 is an analyzer, 8 is a collimator lens, 9 is an output optical fiber, and 10 is an optical receiver.

The operation of this electromagnetic field sensor will be described below. The light emitted from the light source 1 is guided by the input optical fiber 2 to the polarizer 5 via the collimator lens 3.
Since the guided light of the input optical fiber 2 is the same as natural light, it is linearly polarized by the polarizer 5. The magnetic field H is applied to the magneto-optical element 6.
Considering the case where is acting, the linearly polarized light guided to the magneto-optical element 6 is equal to the rotation angle represented by Δφ = VeLH (1) due to the Faraday effect (magnetic rotatory power). Rotate. Here, Ve is the Verdet constant of the magneto-optical element 6, and L is the length of the magneto-optical element 6. The light emitted from the magneto-optical element 6 is modulated in intensity by the analyzer 7, and then guided to the optical receiver 10 through the output optical fiber 9 via the collimator lens 8 and photoelectrically converted.

The magnitude of the applied magnetic field H can be detected by measuring the electric signal corresponding to the light intensity, and if the source of the applied magnetic field is a current, the magnitude of the current can be detected. . Here, if the polarizer 5 and the analyzer 7 are arranged at an inclination of 45 °, the intensity of the incident light on the magneto-optical element 6 is Io, and the intensity of the emitted light of the analyzer 7 is I,
The following equation holds. I = 1 / 2Io [1 + sin (2LVeH)] ... (2)

[0005]

Since the conventional electromagnetic field sensor is constructed as described above, the intensity I of the emitted light depends on the Verdet constant Ve from the equation (2), and this Verdet constant Ve depends on the temperature. However, there is a problem that when the same magnetic field is detected, the detected amount varies due to the temperature change.

Conventionally, as a magneto-optical element used in an electromagnetic field sensor or the like, a diamagnetic material shown in Table 1 or a magnetic garnet crystal with temperature compensation in some cases has been used.

[0007]

[Table 1]

Further, in recent years, as a magneto-optical element such as an optical isolator, a rare earth iron garnet crystal has been developed in which bismuth substitution having a Verdet constant larger than that of a conventional magnetic garnet crystal by one digit is performed. When this bismuth-substituted rare earth iron garnet crystal is used as a magneto-optical element, the bismuth-substituted rare earth iron garnet crystal differs from the materials shown in Table 1 in that the absorption coefficient increases in proportion to temperature, so the temperature range to be detected is narrow. In the case of use in an environment where there are drawbacks and the temperature changes greatly, it is necessary to correct the detection result.

As a method of correction, for example, the temperature of the measuring section is measured by a thermocouple or the like, and the output result is corrected by the electronic circuit section of the optical receiver based on the measurement result. Install the measurement section and the electronic circuit section of the optical receiver in the same temperature environment, measure the temperature of the electronic circuit section with a thermistor, etc., and correct the output result in the electronic circuit section of the optical receiver based on the measurement result. A correction means such as, is required. In this case, a temperature sensor such as a thermocouple needs to be installed at the same time, which leads to an increase in the size of the device and an increase in cost. In this case, since the operating temperature range of the electronic circuit section of the optical receiver is generally limited to around room temperature, there is a problem that the operating temperature environment is significantly limited.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide an electromagnetic field sensor which can be used in a wide temperature range without being affected by temperature. In order to achieve the above object, the present invention has the following means.

The electromagnetic field sensor according to claim 1 of the present invention is
In an electromagnetic field sensor that includes a polarizer, an analyzer, and a detector having a magneto-optical element, and detects a current or a magnetic field by using the Faraday effect of the magneto-optical element, two detectors are arranged in parallel, The detection unit is a magneto-optical element having flat temperature characteristics in the low temperature region, and the other detection unit is a magneto-optical element having flat temperature characteristics in the high temperature region.

The electromagnetic field sensor according to claim 2 of the present invention is
The magneto-optical element is a bismuth-substituted rare earth iron garnet crystal.

The electromagnetic field sensor according to claim 3 of the present invention is
A magneto-optical element with flat temperature characteristics in the low temperature range has a large rate of change in the temperature characteristics in the high temperature range, and a magneto-optical element with flat temperature characteristics in the high temperature range has a large rate of change in the temperature characteristics in the low temperature range. And

The electromagnetic field sensor according to claim 4 of the present invention is
A magneto-optical element with flat temperature characteristics in the low temperature range has an increased rate of change in the temperature characteristics in the high temperature area, and a magneto-optical element with flat temperature characteristics in the high temperature area has an increased rate of change in the temperature characteristics in the low temperature range. Is characterized by.

The electromagnetic field sensor according to claim 5 of the present invention is
A magneto-optical element with a flat temperature characteristic in the low temperature range has a reduced rate of change in the temperature characteristic in the high temperature range, and a magneto-optical element with a flat temperature characteristic in the high temperature range has a reduced rate of change in the temperature characteristic in the low temperature range. Is characterized by.

[0016]

According to the electromagnetic field sensor of the present invention, when the current and magnetic field are measured in the low temperature region, the detection is carried out by the detection unit having the magneto-optical element having flat temperature characteristics in the low temperature region.
When measuring the current and magnetic field in the high temperature range, the temperature characteristic of the high temperature range is detected by the detector that has a flat magneto-optical element.
Wide temperature range from low temperature to high temperature can be measured without correcting the detection result.

According to the electromagnetic field sensor of the present invention, since the magneto-optical element is a bismuth-substituted rare earth iron garnet crystal, the electromagnetic field sensor having a large Verdet constant and a high sensitivity is detected. Can be

[0018]

【Example】

(Example 1) The present invention will be described in detail below with reference to examples. The same parts as those of the conventional one are designated by the same reference numerals and detailed description thereof will be omitted. In FIG. 1, 1 to 5 and 7 to 10 are a light source, an optical fiber, a collimator lens, a total reflection mirror, a polarizer, an analyzer, a collimator lens, an optical fiber, and an optical receiver, respectively, as in the case of FIG. Each operates in the same way as in FIG. The difference from FIG. 7 is that the light emitted from the collimator lens 3 is split into two by the half mirror 11. First, the light reflected by the half mirror 11 enters the detection unit A (polarizer 5, magneto-optical element 6A, analyzer 7). In addition, the light transmitted through the half mirror 11 is detected by the detection unit B.
(The polarizer 5, the magneto-optical element 6B, and the analyzer 7) enter.

The light entering the detection section A is guided to the polarizer 5 and is incident on the magneto-optical element 6A. Magneto-optical element 6A, 6
The light emitted from B is light-intensity-modulated by analyzers 7 and 7, respectively, and is guided to the optical receiver 10 through the output optical fibers 9 and 9 through the collimator lenses 8 and 8 and is photoelectrically converted.

By measuring the electric signal corresponding to this light intensity, the magnitude of the applied magnetic field H can be detected, and if the source of the applied magnetic field is a current, the magnitude of the current can be detected. . By the way, the magneto-optical element 6A is composed of a bismuth-substituted rare earth iron garnet crystal,
The component is (BiR) ₃ Fe ₅ O _{12 in} which R is replaced by Ho (holmium). The temperature characteristics (temperature and output change rate) of the Faraday effect are as shown in FIG. 2, and the change rate of change rate is a constant flat temperature range from 15 ° C. to 60 ° C. The rate of change tends to increase from to around -20 ° C.

The magneto-optical element 6B is the magneto-optical element 6
Like A, it is composed of a bismuth-substituted rare earth iron garnet crystal, and its component is (BiR) ₃ Fe ₅ O _{12 in} which R is replaced with Er (eurobiim). The temperature characteristic of the Faraday effect (temperature and output change rate) is as shown in FIG. 3, and the change rate of change is a constant flat temperature range from −20 ° C. to 27 ° C. The rate of change tends to increase from ℃ to 60 ℃.

When measuring current with this electromagnetic field sensor,
Two types of measurement values detected by the detection unit A and the detection unit B are read by the optical receiver 10. Therefore, when the optical receiver 10 reads two measured values, the optical receiver 10 is provided with a measured value comparison circuit so that the two measured values are compared and the lower one is read as the correct measured value. 12 is a comparison circuit for the measured values. That is, when the measurement range is, for example, −10 ° C., the measurement value of the detection unit A has a temperature characteristic of the Faraday effect of the magneto-optical element 6A that is on the + side due to an increase in the rate of change. The rate of change of the temperature characteristic of is 0, but the measured value is large. Further, when the measurement range is, for example, 50 ° C., the measured value of the detection unit B has a change rate of the temperature characteristic of the Faraday effect of the magneto-optical element 6B that is on the + side, so that the Faraday effect of the magneto-optical element 6A is The rate of change of the temperature characteristic is 0, but the measured value is large.

Therefore, in both the low temperature side and the high temperature side,
The lower the measured value, the more accurate the measured value. As a result, as shown in FIG. 4, the magneto-optical elements 6A and 6B cover the flat temperature range of the rate of change of the temperature characteristics of the Faraday effect, that is, from -20 ° C to 60 ° C.

(Example 2) Magneto-optical element 6A of Example 1
The change rate of the temperature characteristics of the Faraday effect of 15 to 60
It consists of a bismuth-substituted rare earth iron garnet crystal that has a constant flat temperature range in which the change rate is constant up to ℃, and tends to increase from 15 ℃ to -20 ℃. However, as shown in Figure 6,
It is also possible to use the magneto-optical element 6A in which the change rate is in a flat temperature range where the change rate is constant up to about 20 degrees Celsius, and the change rate tends to decrease from 13 degrees Celsius to −20 degrees Celsius.

The component of this magneto-optical element 6A is (BiR)
₃ Fe ₅ O _{12 in} which R is replaced with Y (yttrium). When the magneto-optical element 6A in which R is replaced by Y is used, the rate of change in the temperature characteristics of the Faraday effect of the magneto-optical element 6B is from -20 ° C to 27 ° C as shown in FIG.
The magneto-optical element 6B is used which has a constant flat temperature range in which the change rate is constant up to about 70 degrees Celsius, and which tends to decrease from 27 degrees Celsius to 60 degrees Celsius. The component of this magneto-optical element 6B can be obtained by substituting R for both Y (yttrium) and Dy (dysprosium) with (BiR) ₃ Fe ₅ O ₁₂ .

When the magneto-optical elements 6A and 6B are used, when the two measured values are read by the optical receiver 10, the first embodiment is used.
In contrast to the above case, the measured value comparison circuit 11 compares the two measured values and reads the higher one as the correct measured value.
Need to be configured.

[0027]

As described above, the claims 1 to 3 of the present invention are as follows.
According to the electromagnetic field sensor of No. 5, when measuring the current and magnetic field in the low temperature range, the detection unit having a magneto-optical element having a flat temperature characteristic in the low temperature range detects the current and the magnetic field in the high temperature range. Since detection is performed by the detection unit having a magneto-optical element having a flat temperature characteristic in the high temperature range, a wide temperature range from the low temperature range to the high temperature range can be measured without correcting the detection result.

According to the electromagnetic field sensor of claims 2 to 5 of the present invention, since the magneto-optical element is a bismuth-substituted rare earth iron garnet crystal, an electromagnetic field sensor having a large Verdet constant and a high sensitivity is used. can do.

According to the electromagnetic field sensor of the third aspect of the present invention, of the measurement values of the two detectors, one of the measurement values having a higher or lower measurement value can be determined as an accurate measurement value. Therefore, an accurate measurement value can be obtained with a simple circuit.

According to the electromagnetic field sensor of claim 4 of the present invention, the measured value of the lower one of the measured values of the two detectors can be determined as an accurate measured value. It is possible to obtain various measured values.

According to the electromagnetic field sensor of claim 4 of the present invention, of the measured values of the two detectors, the one with the higher measured value can be determined as an accurate measured value. It is possible to obtain various measured values.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an electromagnetic field sensor of the present invention.

FIG. 2 is a temperature characteristic diagram of a magneto-optical element used in the electromagnetic field sensor of the present invention.

FIG. 3 is a temperature characteristic diagram of another magneto-optical element used in the electromagnetic field sensor of the present invention.

FIG. 4 is a temperature characteristic diagram of another magneto-optical element used in the electromagnetic field sensor of the present invention.

FIG. 5 is a temperature characteristic diagram of another magneto-optical element used in the electromagnetic field sensor of the present invention.

FIG. 6 is a temperature characteristic diagram of another magneto-optical element used in the electromagnetic field sensor of the present invention.

FIG. 7 is an explanatory diagram of a conventional electromagnetic field sensor.

[Explanation of symbols]

 1 Light Source 2 Input Optical Fiber 3 Collimator Lens 4 Total Reflection Mirror 5 Polarizer 6A, 6B Magneto-Optical Element 7 Analyzer 8 Collimator Lens 9 Output Optical Fiber 10 Optical Receiver 11 Half Mirror 12 Measurement Value Comparison Circuit A, B Detection unit

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takaaki Kubozono 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (5)

[Claims] 1. An electromagnetic field sensor that includes a polarizer, an analyzer, and a detector having a magneto-optical element, and detects a current or a magnetic field by utilizing the Faraday effect of the magneto-optical element. The electromagnetic field sensor is characterized in that one detecting section is a magneto-optical element having a flat temperature characteristic in a low temperature range, and the other detecting section is a magneto-optical element having a flat temperature characteristic in a high temperature range. . 2. The electromagnetic field sensor according to claim 1, wherein the magneto-optical element is a bismuth-substituted rare earth iron garnet crystal. 3. A magneto-optical element having a flat temperature characteristic in the low temperature range has a large rate of change in the temperature characteristic in the high temperature range, and a magneto-optical element having a flat temperature characteristic in the high temperature range has a rate of change in the temperature characteristic in the low temperature range. The electromagnetic field sensor according to claim 1 or 2, characterized in that 4. A magneto-optical element having a flat temperature characteristic in the low temperature range has a high rate of change in the temperature characteristic in the high temperature range, and a magneto-optical element having a flat temperature characteristic in the high temperature range has a change in the temperature characteristic in the low temperature range. The electromagnetic field sensor according to any one of claims 1 to 3, wherein the rate is increased. 5. A magneto-optical element having a flat temperature characteristic in the low temperature range has a reduced rate of change in the temperature characteristic in the high temperature range, and a magneto-optical element having a flat temperature characteristic in the high temperature range has a change in the temperature characteristic in the low temperature range. The electromagnetic field sensor according to claim 1, wherein the rate is reduced.