JPH09280971A - Magnetostrictive sensor temperature compensator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the temperature detected value exhibiting flat temperature characteristics compensated for negative temperature characteristics by compensating the negative temperature characteristics exhibited by the stress detected value based on the stress detected value detected by stress detecting means and the temperature detected value detected by temperature detecting means. SOLUTION: When a compression force is applied to an magnetostrictive element 3, the permeability of the applying direction is increased, the symmetry of the magnetic flux distribution by an exciting coil 5a is collapsed, the voltage proportional to the force is generated in a detecting coil 5b, and a first amplifier 23 outputs a first voltage Vo exhibiting negative temperature characteristics. Exciting power 19 is supplied from an AC exciting power source 19 to the coil 5a. Even if the atmospheric temperature around a magnetostrictive sensor 1 is varied so that the resistance value of the coil 5a is varied, the current value flowing to the coil 5a does not alter, but is maintained at a predetermined value, and the amplitude of the excited voltage applied to the coil 5a is varied. That is, a second voltage Vt exhibits the positive temperature characteristics for raising the voltage value as the temperature rises. This is canceled by the first voltage Vo of the negative temperature characteristics to obtain the compensated output voltage Vot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention excites a magnetostrictive sensor in which a coil is wound around a magnetostrictive element made of a magnetic material, and the magnetization characteristic of the magnetic material changes when a force is applied to the magnetostrictive element. The present invention relates to a magnetostrictive sensor that detects an applied force by using, in particular, so as to compensate for a decrease in accuracy of the sensor detected value due to a change in the detected value of the magnetostrictive sensor depending on a temperature change. The present invention relates to a temperature compensation device for a magnetostrictive sensor.

[0002]

2. Description of the Related Art Generally, in order to measure the force applied to a certain substance, various means are known for detecting the magnitude of the force by utilizing the fact that the physical properties change due to the application of the force. . Among them, the magnetostrictive sensor has features that the structure is simple and the mechanical strength is high, it is difficult to be affected by disturbance noise, and the output of the magnetostrictive sensor is low because the impedance of the detection element is low. It is used for applications such as the weight of trucks. This magnetostrictive sensor
The magnitude of the applied force is measured using the principle that a magnetostrictive sensor made by winding a coil around a magnetostrictive element made of a magnetic material is excited, and the magnetic characteristics of the magnetic material change when a force is applied to the magnetostrictive element. I'm trying to detect.

More specifically, the conventional magnetostrictive sensor is made of a magnetic material having four through holes aligned in a square shape in its central portion, as disclosed in, for example, Japanese Patent Laid-Open No. 6-313740. And a pair of coils in which electric wires are wound around the pair of through-holes located diagonally among these four through-holes in a peg shape through these through-holes. . One of the coils is an exciting coil, and a pair of lead wires drawn from this coil are connected to an alternating-current exciting power supply that supplies an alternating voltage whose effective value is controlled to be constant to the exciting coil. The other coil is a detection coil, and a pair of lead wires drawn from this coil rectifies and smoothes an AC voltage signal generated in the detection coil according to the stress applied to the magnetostrictive sensor. It is connected to a display instrument such as a voltmeter through a circuit and a DC amplification circuit that amplifies the voltage signal converted into DC by the rectification circuit.

Here, the principle of stress detection of the magnetostrictive sensor will be described. When mechanical strain is applied to the magnetic substance, the magnetization characteristics of the magnetic substance, particularly the transparent property, are increased between the lengthwise extending direction and the lengthwise contracting direction. There is a big difference in magnetic susceptibility. For example, considering a case where a compressive stress is applied to a magnetostrictive element from a certain direction, the magnetic permeability decreases in the stressed direction, while the magnetic permeability increases in the direction perpendicular to the stressed direction. As a result, in the state where no compressive stress is applied, the magnetic flux distribution in the magnetostrictive element maintains symmetry, and there is no magnetic flux that intersects the detection coil and no voltage is generated in the detection coil, whereas when compressive stress is applied, The symmetry of the magnetic flux distribution collapses to generate a magnetic flux that intersects the detection coil, and a voltage proportional to the applied compressive stress occurs in the detection coil.
Therefore, it is possible to know the compressive stress applied to the magnetostrictive element by measuring this voltage value.

[0005]

However, in the above-mentioned conventional magnetostrictive sensor, the sensor detection value includes an error due to the fluctuation of the ambient temperature around the sensor, and due to this error, the sensor There is a problem that it is difficult to improve the detection accuracy.

More specifically, in the peripheral equipment connected to the conventional magnetostrictive sensor, for example, in an AC excitation power source for exciting the exciting coil, the effective value is constant with respect to the exciting coil. Although a controlled AC voltage is supplied, if the resistance value of the exciting coil changes due to changes in the ambient temperature around the magnetostrictive sensor, the value of the current flowing in the exciting coil also changes, which in turn causes the exciting coil to be generated. The magnetic flux is also displaced, and the magnetic flux including this displacement is detected by the detection coil, and as a result, the detected value of the compressive stress applied to the magnetostrictive element includes an error.

Therefore, in order to eliminate the error in the sensor detection value due to such a change in ambient temperature, an AC excitation power supply of a form in which an AC current whose effective value is controlled to be constant is supplied to the excitation coil. Is proposed to be used. According to this proposal, even if the resistance value of the exciting coil changes due to the change of the ambient temperature around the sensor, the value of the current flowing through the exciting coil does not change, and the displacement of the magnetic flux generated by the exciting coil is reduced. Can be suppressed. However, even if this proposal is adopted, it has been experimentally found that the error in the sensor detection value cannot be completely removed. That is, in the state where no stress is applied to the magnetostrictive sensor, an alternating current whose effective value is controlled to be constant is supplied to the exciting coil, and the ambient temperature around the sensor is changed. When observing the output voltage of the detection coil at that time, it was found that the output voltage of the detection coil exhibits a so-called negative temperature characteristic in which the voltage value decreases in accordance with the rise in temperature. It is estimated that this is due to the fact that the magnetization characteristics of the magnetic substance that constitutes the magnetostrictive element are displaced due to fluctuations in the ambient temperature, but the fact is that no measures have been taken in the past. There was a strong demand among the parties concerned to solve these problems.

The present invention has been made in view of the above-mentioned circumstances, and the output voltage of the detection coil, which includes an error caused by the fluctuation of the ambient temperature around the magnetostrictive sensor, has an effective value with respect to the excitation coil. In the mode in which the AC current is controlled to be constant, compensation is performed using the voltage amplitude value that fluctuates according to the fluctuation of the ambient temperature around the magnetostrictive sensor, so that the error in the sensor detection value is removed and the sensor An object of the present invention is to provide a temperature compensation device for a magnetostrictive sensor that can improve detection accuracy.

[0009]

In order to solve the above-mentioned problems, the invention of claim 1 is such that a coil is wound around a magnetostrictive element made of a magnetic material, and this magnetostrictive element is excited,
In a magnetostrictive sensor configured to detect the magnitude of the applied stress by utilizing the fact that the magnetization characteristics of the magnetic body change when stress is applied to the magnetostrictive element, the effective value is a constant current. An alternating current excitation power source for supplying a controlled alternating current, a constant current is supplied from the alternating current excitation power source, an excitation coil for exciting the magnetostrictive element, and is arranged to intersect perpendicularly to the excitation coil, A detection coil for detecting a change in the magnetization characteristic when stress is applied to the magnetostrictive element, and a stress detection signal in the form of an AC voltage generated in the detection coil, a DC voltage form adjusted to an appropriate level. A stress detection means for converting the stress detection value and outputting the stress detection value, and a temperature detection signal in the DC voltage form adjusted to an appropriate level for the temperature detection signal in the AC voltage form applied to the exciting coil from the AC excitation power supply. Strange A temperature detection means for and outputs,
Compensation means for compensating for the negative temperature characteristic exhibited by the stress detection value based on the stress detection value detected by the stress detection means and the temperature detection value detected by the temperature detection means. That is the summary.

According to the first aspect of the present invention, first, the exciting coil of the magnetostrictive sensor is supplied with alternating current whose effective value is controlled to be a constant current from the alternating current exciting power source. At this time, if no stress is applied to the magnetostrictive element, the magnetic flux distribution in the magnetostrictive element maintains symmetry with respect to the exciting coil, and as a result, there is no magnetic flux that intersects the detecting coil, and there is no voltage across the detecting coil. Does not occur. On the other hand, for example, when compressive stress is applied to the magnetostrictive element, the magnetic permeability decreases in the stressed direction, while the magnetic permeability increases in the direction perpendicular to the stressed direction, and the magnetic flux generated by the exciting coil is increased. The symmetry of the distribution is broken, and as a result, a magnetic flux intersecting the detection coil is generated in the magnetostrictive element, and a voltage proportional to the applied compressive stress is generated in the detection coil. The AC voltage type stress detection signal from the detection coil is converted into a DC voltage type stress detection value adjusted to an appropriate level in the stress detecting means, and the stress detecting means follows the temperature characteristic of the magnetostrictive element. The detected stress value that exhibits a negative temperature characteristic is output.

In order to compensate for the negative temperature characteristic of the stress detection value, the invention of claim 1 detects the ambient temperature around the magnetostrictive sensor from the AC voltage applied from the AC excitation power source to the exciting coil. I am trying. Explaining this, the excitation coil is supplied with alternating current whose effective value is controlled to be constant from an alternating current excitation power source.However, when the ambient temperature around the magnetostrictive sensor fluctuates, the resistance value of the exciting coil fluctuates. However, the value of the current flowing through the exciting coil also tries to change. However, since the effective value is controlled to a constant current by the AC excitation power supply, even if the resistance value of the exciting coil fluctuates due to fluctuations in the ambient temperature around the magnetostrictive sensor, the current value flowing in the exciting coil fluctuates. Without being kept constant, the amplitude of the exciting voltage applied to the exciting coil changes. According to Ohm's law, this amplitude fluctuation of the exciting voltage exhibits a positive temperature characteristic of increasing the voltage value as the temperature rises. Therefore, the voltage applied to the exciting coil is changed to the atmosphere around the magnetostrictive sensor. It can be regarded as temperature. That is, the temperature detecting means converts the temperature detection signal of the AC voltage form applied from the AC excitation power source to the exciting coil into a temperature detection value of the DC voltage form adjusted to an appropriate level and outputs the temperature detected value. The compensating means compensates the negative temperature characteristic exhibited by the stress detection value based on the stress detection value detected by the stress detection means and the temperature detection value detected by the temperature detection means, thereby It is possible to obtain a stress detection value exhibiting a flat temperature characteristic in which the temperature characteristic is compensated. Since the stress detection value obtained here is a value that faithfully reflects the stress applied to the magnetostrictive element, as a result, the error in the sensor detection value can be removed and the detection accuracy of the sensor can be improved. it can. Moreover, since the ambient temperature around the magnetostrictive sensor is detected from the voltage applied to the exciting coil without separately providing a temperature detecting element such as a thermistor, the difference in heat capacity between the magnetostrictive sensor itself and the temperature detecting element is detected. The temperature compensation of the stress detection value can be realized with a simple circuit configuration without taking into consideration.

According to a second aspect of the present invention, the compensating means adds the stress detection value detected by the stress detecting means and the temperature detection value detected by the temperature detecting means to obtain the stress. The gist is to compensate for the negative temperature characteristic exhibited by the detected value.

According to the second aspect of the present invention, the compensating means includes the stress detection value exhibiting the negative temperature characteristic detected by the stress detecting means and the temperature detection value exhibiting the positive temperature characteristic detected by the temperature detecting means. By adding and, it is possible to obtain the stress detection value exhibiting a flat temperature characteristic in which the negative temperature characteristic exhibited by the stress detection value is compensated by the offset.

Further, the invention of claim 3 further comprises storage means for storing a correction table representing a correction coefficient corresponding to an ambient temperature around the magnetostrictive sensor, and the compensation means is stored in the storage means. By reading a correction coefficient corresponding to the temperature detection value detected by the temperature detection means from the correction table and multiplying the stress detection value detected by the stress detection means by the read correction coefficient, The gist is to compensate the negative temperature characteristic exhibited by the stress detection value.

According to the third aspect of the invention, the compensating means reads the correction coefficient corresponding to the temperature detection value detected by the temperature detecting means from the correction table stored in the storing means,
The stress detection value detected by the stress detection means is multiplied by the read correction coefficient to obtain the stress detection value exhibiting a flat temperature characteristic in which the negative temperature characteristic exhibited by the stress detection value is compensated. You can

The invention according to claim 4 further comprises a display means for displaying the stress detection value compensated by the compensation means.

According to the invention of claim 4, the stress detection value displayed on the display means is a value that faithfully reflects the stress applied to the magnetostrictive sensor. Therefore, by reading the indication value on the display means. The applied stress can be known accurately.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, two embodiments of a temperature compensating device for a magnetostrictive sensor according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram according to the first embodiment of the present invention, FIG. 2 is a circuit diagram showing a part of the first embodiment of the present invention, and FIGS. 3 to 5 are explanations of the present invention. FIG. 6 is a schematic configuration diagram according to the second embodiment of the present invention,
FIG. 7 is an operation flowchart diagram according to the second embodiment of the present invention. In the description of this embodiment, common members are denoted by common reference numerals, and duplicated description will be omitted.

First, as shown in FIG. 1, the magnetostrictive sensor 1 according to the first embodiment of the present invention includes a magnetostrictive element 3 made of a magnetic material such as permendur, and the magnetostrictive element 3.
And a coil 5 wound around. As the magnetic material forming the magnetostrictive element 3, for example, permalloy or soft iron can be used. More specifically, the magnetostrictive element 3
There are four through holes 7 in the center of the
These through holes 7 are formed in a square shape and the bottom side thereof is arranged parallel to the bottom surface of the magnetostrictive element 3. With such an arrangement of the through holes 7, the compressive or tensile stress on the magnetostrictive element 3 can be efficiently detected. In these four through holes 7, an electric wire is wound around each of a pair of diagonally located through holes through the through holes, and the pair of coils 5a and 5b are formed with this. To do. The coil 5a is an excitation coil, and the pair of lead wires 9a and 9b of the coil 5a are excitation side terminals 13a and 13b.
An exciting amplifier 1 for amplifying the output power from the power supply 19 to an appropriate value by connecting an AC exciting power supply 19 for supplying an alternating current whose effective value is controlled to a constant current through
7 is connected.

On the other hand, the coil 5b is a detection coil, and the pair of lead wires 11a and 11b of the coil 5b are connected to the detection side terminals 15a and 15b, respectively, through an alternating current corresponding to the stress generated in the detection coil 5b. A stress detection circuit 2 for converting the output voltage to DC and amplifying the converted value to an appropriate value to output the first voltage Vo as a stress detection value.
5 is connected. The stress detection circuit 25 rectifies and smoothes the AC output voltage generated in the detection coil 5b.
The rectifier circuit 21 and the first amplifier circuit 23 that amplifies the DC output voltage from the first rectifier circuit 21 to an appropriate value.

In parallel with the stress detecting circuit 25, a pair of lead wires 27a, 2 are connected to the exciting side terminals 13a, 13b.
The AC voltage, which is applied to the exciting coil 5a via the 7b and has a voltage amplitude value that fluctuates according to the fluctuation of the ambient temperature around the magnetostrictive sensor 1, is converted into a direct current, and the converted value is converted into an appropriate value. It is connected to a temperature detection circuit 33 which amplifies the value and outputs a second voltage Vt as a temperature detection value. The temperature detection circuit 33 includes a second rectifier circuit 29 that rectifies and smoothes the AC voltage applied to the exciting coil 5a, and a second rectifier circuit that amplifies the DC voltage from the second rectifier circuit 29 to an appropriate value. It is composed of an amplifier circuit 31.

Each of the stress detection circuit 25 and the temperature detection circuit 33 has a first voltage Vo output from these circuits.
, And the second voltage Vt are added to connect to the temperature compensation circuit 35 which outputs the third voltage Vot which is the stress detection value after temperature compensation. The temperature compensation circuit 35 is connected to a voltmeter 37 that displays the third voltage Vot output from the temperature compensation circuit 35.

Next, the temperature compensation circuit 35 will be described in more detail. As shown in FIG. 2, the first voltage Vo as the stress detection value output from the stress detection circuit 25 is the first voltage Vo.
The second voltage Vt as the temperature detection value output from the temperature detection circuit 33 is input to the inverting input terminal of the operational amplifier 43 via the resistor 39 in series, and the second voltage Vt output from the temperature detection circuit 33 is output via the second resistor 41 in series. It is input to the inverting input terminal 43.
The non-inverting input terminal of the operational amplifier 43 is grounded. The output terminal 45 of the operational amplifier 43 is connected to the inverting input terminal via the third resistor 47 and the connection point 42.
As a result, part of the third voltage Vot is returned to the input side of the operational amplifier 43 by the first, second, and third resistors 39, 41, and 47 functioning as negative feedback resistors, and circuit operation by negative feedback action is performed. Is being stabilized.

The circuit operation of the temperature compensating device for the magnetostrictive sensor according to the present invention constructed as described above will be described with reference to FIGS.

First, the exciting coil 5a of the magnetostrictive sensor 1
An AC exciting current whose effective value is controlled to be constant is supplied from an AC exciting power source 19 via an exciting amplifier 17. At this time, if no stress is applied to the magnetostrictive element 3, the magnetic flux distribution in the magnetostrictive element 3 maintains symmetry with respect to the exciting coil 5a, and as a result, there is no magnetic flux that intersects with the detecting coil 5b. No voltage is generated in the coil 5b. On the other hand, when compressive stress as shown in FIG. 1 is applied to the magnetostrictive element 3, the magnetic permeability decreases in the stressed direction, while the magnetic permeability increases in the direction perpendicular to the stressed direction. The symmetry of the magnetic flux distribution by the exciting coil 5a is destroyed, and as a result, a magnetic flux intersecting the detecting coil 5b is generated in the magnetostrictive element 3, and a voltage proportional to the applied compressive stress is generated in the detecting coil 5b. To do.
The AC output voltage generated in the detection coil 5b is rectified and smoothed by the first rectifier circuit 21, and amplified by the first amplifier circuit 23 to an appropriate value. The first voltage Vo exhibiting the negative temperature characteristic shown in is output.

In order to compensate for the negative temperature characteristic of the first voltage Vo, according to the present invention, the amplitude of the exciting voltage that fluctuates so as to exhibit a positive temperature characteristic as the ambient temperature around the magnetostrictive sensor 1 changes. The value is adopted. Explaining this, the exciting coil 5a of the magnetostrictive sensor 1 of the present invention is supplied with an AC exciting current whose effective value is controlled to be constant from an AC exciting power source 19 through an exciting amplifier 17, but the magnetostriction is generated. When the ambient temperature around the sensor 1 fluctuates, the resistance value of the exciting coil 5a fluctuates, and the current value flowing through the exciting coil 5a also tends to fluctuate. However, the AC exciting power source 19 whose effective value is controlled to a constant current causes the exciting coil 5a to change due to a change in ambient temperature around the magnetostrictive sensor 1.
Even if the resistance value changes, the value of the current flowing through the exciting coil 5a does not change and is maintained at a constant value, and the amplitude of the exciting voltage applied to the exciting coil 5a changes. Amplitude fluctuation of this excitation voltage, that is, the second voltage Vt
In accordance with Ohm's law, as shown in FIG. 4, exhibits a positive temperature characteristic of increasing the voltage value as the temperature rises. In the present invention, by adding the first voltage Vo exhibiting the negative temperature characteristic and the second voltage Vt exhibiting the positive temperature characteristic, the negative temperature characteristic is canceled as shown in FIG. The compensated output voltage Vot is obtained.

The first resistor 39 and the second resistor 41 are added at the connection point 42 via the first and second resistors 39 and 41, respectively, and the added voltage value is inverted by the operational amplifier 43. It is input to the input terminal. Then, the third voltage Vot amplified in accordance with the distribution ratio of the resistance values of the first and second resistors 39 and 41 and the third resistor 47 is output from the output terminal of the operational amplifier 43. This output voltage Vot is input to the voltmeter 37, but the temperature characteristic of the third voltage Vot displayed on the voltmeter 37 is compensated by the temperature compensating circuit 35, and the stress applied to the magnetostrictive sensor 1 is Since the value faithfully reflects, the applied stress can be accurately known by reading the indicated value of the voltmeter 37. Moreover,
Since the ambient temperature around the magnetostrictive sensor 1 is detected from the exciting voltage applied to the exciting coil 5a without separately providing a temperature detecting element such as a thermistor, the heat capacity between the magnetostrictive sensor 1 itself and the temperature detecting element is detected. The temperature compensation of the stress detection value can be realized with a simple circuit configuration without considering the difference between

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 to 7. The temperature compensating device of the second embodiment employs the same principle of compensating temperature as that of the first embodiment, and the device configuration is almost the same. Therefore, the difference between the two will be described. Instead of the description of the configuration of the embodiment.

That is, the temperature compensating apparatus of the second embodiment is connected to the stress detecting circuit 25 and the temperature detecting circuit 33 instead of the temperature compensating circuit 35 of the first embodiment, and the stress output from these circuits is connected. The first voltage Vo as a detection value,
And the second voltage Vt as the temperature detection value are sequentially input, and the input analog signals are converted into digital signals Vo and V.
A / D conversion circuit 51 for converting to t and A / D conversion circuit 5
Input the digital signals Vo and Vt from 1 respectively,
A CPU 53 for performing a calculation for compensating for the negative temperature characteristic exhibited by the voltage proportional to the compressive stress applied to the magnetostrictive sensor 1, transferring the compensated voltage value to the voltmeter 37, a ROM 55 for storing a program, RA that stores the data acquired via the CPU 53 and a correction table that represents a correction coefficient corresponding to the ambient temperature around the magnetostrictive sensor 1.
M57 and is additionally adopted.

Next, the operation of the above-mentioned second embodiment will be described with reference to the flow chart of FIG. 7. First, the CPU 53 firstly converts the digital signal Vo from the first voltage Vo and the second voltage Vt. , Vt are input and these values are stored in a predetermined address of the RAM 57 (step S1). Here, the digital signal Vo is treated as a stress detection value, while the digital signal Vt is treated as a temperature detection value. Next, the CPU 53
A table lookup is performed by referring to the digital signal Vt read from the AM 57 and the correction table, the correction coefficient corresponding to the current ambient temperature around the magnetostrictive sensor 1 is read, and the read correction coefficient is read from the RAM 57. An operation for multiplying the signal Vo is performed, and the operation result is stored as Vot in a predetermined address of the RAM 57 (step S3). Then, the CPU 53 causes the RAM 5
The calculation result Vot read from 7 is transferred to the voltmeter 37,
The obtained calculation result Vot is displayed on the voltmeter 37. The temperature characteristic of the calculation result Vot displayed on the voltmeter 37 is compensated by the CPU 53 and is a value that faithfully reflects the stress applied to the magnetostrictive sensor 1. Therefore, read the indicated value of the voltmeter 37. The stress applied by can be known accurately.

In the present embodiment, the form of the magnetostrictive sensor preferable for detecting the compressive or tensile stress is illustrated, but the present invention is not limited to this, and four through holes formed in the magnetostrictive element. The arrangement can also be applied to a magnetostrictive sensor having a square shape and one side of which is positioned at an angle of 45 ° with the bottom surface of the magnetostrictive element to detect shear stress on the magnetostrictive element.

[0033]

As described above, according to the invention of claim 1, the compensating means is based on the stress detected value detected by the stress detecting means and the temperature detected value detected by the temperature detecting means. By compensating the negative temperature characteristic exhibited by the stress detection value, it is possible to obtain the stress detection value exhibiting a flat temperature characteristic in which the negative temperature characteristic is compensated. Since the stress detection value obtained here is a value that faithfully reflects the stress applied to the magnetostrictive element, as a result, the error in the sensor detection value can be removed and the detection accuracy of the sensor can be improved. it can.
Moreover, since the ambient temperature around the magnetostrictive sensor is detected from the voltage applied to the exciting coil without separately providing a temperature detecting element such as a thermistor, the difference in heat capacity between the magnetostrictive sensor itself and the temperature detecting element is detected. Without considering
The temperature compensation of the stress detection value can be realized with a simple circuit configuration.

According to the second aspect of the present invention, the compensating means includes the stress detection value having the negative temperature characteristic detected by the stress detecting means and the temperature having the positive temperature characteristic detected by the temperature detecting means. By adding the detected value and the detected value, it is possible to obtain a stress detected value exhibiting a flat temperature characteristic in which the negative temperature characteristic exhibited by the stress detected value is compensated for by cancellation.

Further, according to the invention of claim 3, the compensating means reads the correction coefficient corresponding to the temperature detection value detected by the temperature detecting means from the correction table stored in the storing means, and the stress detecting means By multiplying the detected stress detection value by the read correction coefficient, the stress detection value exhibiting a flat temperature characteristic in which the negative temperature characteristic exhibited by the stress detection value is compensated can be obtained.

According to the fourth aspect of the present invention, the detected stress value displayed on the display means is a value that faithfully reflects the stress applied to the magnetostrictive sensor. Therefore, the indication value on the display means is read. This has an extremely excellent effect that the applied stress can be known accurately.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a part according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining the present invention.

FIG. 4 is a diagram for explaining the present invention.

FIG. 5 is a diagram for explaining the present invention.

FIG. 6 is a schematic configuration diagram according to a second embodiment of the present invention.

FIG. 7 is an operation flowchart diagram according to the second embodiment of the present invention.

[Explanation of symbols]

1 Magnetostrictive Sensor 3 Magnetostrictive Element 5a Excitation Coil 5b Detection Coil 7 Through Holes 9a, 9b, 11a, 11b, 27a, 27b Lead Wires 13a, 13b Excitation Side Terminal 15a, 15b Detection Side Terminal 17 Excitation Amplifier 19 AC Excitation Power Supply 21 First Rectification Circuit 23 First Amplification Circuit 25 Stress Detection Circuit 29 Second Rectification Circuit 31 Second Amplification Circuit 33 Temperature Detection Circuit 35 Temperature Compensation Circuit 37 Voltmeter 39 First Resistor 41 Second Resistor 42 Connection Point 43 Operational Amplifier 45 Output terminal of operational amplifier 47 Third resistor 51 A / D conversion circuit 53 CPU 55 ROM 57 RAM

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shozo Ashizawa 1-7-1 Yokoi, Shimada City, Shizuoka Prefecture Yazaki Keiki Co., Ltd. (72) Inventor Shinji Narama 1-7-1 Yokoi Shimada City, Shizuoka Yazaki Keiki Stock company

Claims (4)

[Claims] 1. Utilizing the fact that a coil is wound around a magnetostrictive element made of a magnetic material, the magnetostrictive element is excited, and the magnetization characteristics of the magnetic material change when stress is applied to the magnetostrictive element. In the magnetostrictive sensor configured to detect the magnitude of the applied stress, an alternating current excitation power supply for supplying alternating current whose effective value is controlled to a constant current, and a constant current supplied from the alternating current excitation power supply. An exciting coil that excites the magnetostrictive element, and a detecting coil that is disposed so as to intersect the exciting coil perpendicularly and that detects a change in magnetization characteristics when stress is applied to the magnetostrictive element, Stress detection means for converting a stress detection signal in the form of an AC voltage generated in the detection coil into a stress detection value in the form of a DC voltage adjusted to an appropriate level and outputting the stress detection value, and the excitation coil from the AC excitation power supply. The temperature detection signal of the applied AC voltage form is converted to a temperature detection value of the DC voltage form adjusted to an appropriate level and output, and the stress detection value detected by the stress detection unit, A temperature compensating device for a magnetostrictive sensor, comprising: compensating means for compensating a negative temperature characteristic exhibited by the stress detected value based on the temperature detected value detected by the temperature detecting means. 2. The compensating means adds the stress detection value detected by the stress detection means and the temperature detection value detected by the temperature detection means to obtain a negative temperature indicated by the stress detection value. The characteristic is compensated for.
A temperature compensating device for the magnetostrictive sensor according to. 3. A storage means for storing a correction table representing a correction coefficient corresponding to an ambient temperature around the magnetostrictive sensor, wherein the compensating means detects the temperature from the correction table stored in the storage means. The correction coefficient corresponding to the temperature detection value detected by the means is read, and the stress detection value detected by the stress detection means is multiplied by the read correction coefficient to obtain a negative value of the stress detection value. The temperature compensating device for a magnetostrictive sensor according to claim 1, wherein the temperature characteristic is compensated. 4. The temperature compensating device for a magnetostrictive sensor according to claim 1, further comprising display means for displaying the stress detection value compensated by the compensating means.