JP7260871B2 - Displacement sensor - Google Patents

Description

The present invention relates to a displacement sensor that detects a distance, ie, a gap, from an object to be measured without contact.

A displacement sensor using a coil includes an oscillator that supplies an alternating current to the coil and a circuit that detects a signal change due to a change in impedance of the coil. After the oscillation signal of the oscillator is converted into a DC signal by a rectifier, a linearizer generates a signal that varies linearly according to the gap from the object under test (see Patent Documents 1 and 2).

Coils are known to change their impedance depending on temperature. Therefore, in Patent Document 1, the amplitude level of an oscillation signal output from an oscillator having a coil is corrected by temperature. Further, in Patent Document 2, the output of the linearizer is corrected with a correction value according to the temperature.

JP 2015-137888 A JP-A-8-271204

In Patent Document 1, temperature correction is performed before rectification by a rectifier. However, the rectifier also has offset variations with temperature, and the electrical characteristics of the linearizer may also vary with temperature. Therefore, in the technology disclosed in Patent Document 1, there is a possibility that the output signal of the displacement sensor may have temperature dependency to some extent.

In addition, since the signal frequency on the front stage of the rectifier is high, it is easily affected by stray capacitance. It may have an adverse effect.

On the other hand, in Patent Document 2, correction processing is performed by adding the output voltage of the RV converter to the output voltage of the linearizer. It is not possible to linearize the wide range of input/output characteristics of the linearizer.

Further, when temperature correction is performed on the output of the linearizer as in Patent Document 2, a signal that has not undergone temperature correction is input to the linearizer. Especially in the high frequency range, the attenuation of the signal from the rectifier circuit becomes large. may not be possible.

Furthermore, both Patent Documents 1 and 2 are intended to perform correction processing by combining electrical components, and electrical characteristics are likely to fluctuate due to environmental conditions such as temperature and deterioration over time, and failures are also likely to occur. There is a problem of bad sex.

SUMMARY OF THE INVENTION The present invention provides a displacement sensor capable of improving the linearity of a displacement signal with respect to the displacement of an object to be measured by reducing temperature dependence as much as possible while reducing member costs.

In order to solve the above problems, in one aspect of the present invention, an alternating current is supplied to generate an alternating magnetic field, and an eddy current induced in the object to be measured according to the displacement of the position of the object to be measured is generated. a coil for generating an output responsive to
a temperature measuring instrument for measuring the actual temperature around the coil;
Using the correlation between the output of the coil when the temperature around the coil is a predetermined value and the corrected displacement signal indicating the displacement of the position of the object to be measured, which is obtained from the output of the coil and subjected to temperature correction, the A displacement sensor is provided, comprising a displacement signal generator that outputs a corrected displacement signal corresponding to the actual temperature and the output of the coil as a displacement signal indicating the displacement of the position of the object to be measured.

an interpolation processing unit that interpolates a corrected displacement signal corresponding to the actual temperature measured by the temperature measuring instrument from the correlation between the output of the coil at at least one temperature and the corrected displacement signal,
The displacement signal generator may output a corrected displacement signal interpolated by the interpolation processor as the displacement signal.

The interpolation processing section may interpolate the correlation to generate a new correlation such that the correction displacement signal linearly changes with respect to changes in the output of the coil.

The interpolation processing section may generate the correlation at an intermediate temperature between the two temperatures from the correlation between the output of the coil and the corrected displacement signal at at least two temperatures different from each other.

a substrate on which the displacement signal generator is mounted;
a substrate temperature measuring instrument for measuring the temperature of the substrate,
The interpolation processing unit may interpolate the correlation based on the temperature around the coil measured by the temperature measuring device and the temperature of the substrate measured by the substrate temperature measuring device.

a first correlation storage that stores a first correlation between the output of the coil at a first temperature and the corrected displacement signal;
a second correlation storage unit that stores a second correlation between the output of the coil and the corrected displacement signal at a second temperature different from the first temperature;
The interpolation processing unit generates the second correlation by interpolation processing of the first correlation while the displacement sensor performs measurement using the first correlation, and calculates the second correlation. stored in the relational storage,
The displacement signal generator may generate the corrected displacement signal based on the second correlation when the temperature measured by the temperature measuring device changes to the second temperature.

a first correlation storage that stores a first correlation between the output of the coil at a first temperature and the corrected displacement signal;
a second correlation storage unit that stores a second correlation between the output of the coil and the corrected displacement signal at a second temperature different from the first temperature;
When the temperature measured by the temperature measuring instrument changes from the first temperature to the second temperature while the displacement sensor is measuring using the first correlation, the interpolation processing unit performs the The second correlation may be generated by interpolation processing of the first correlation and stored in the second correlation storage unit.

a self-excited oscillation circuit that generates the alternating current by performing an oscillation operation using the impedance of the coil and outputs an oscillation signal;
The oscillation level of the self-excited oscillator circuit may change under the influence of a change in impedance of the coil caused by an eddy current generated in the object to be measured.

ADVANTAGE OF THE INVENTION According to this invention, while being able to reduce member cost, the linearity of the displacement signal with respect to the displacement of a to-be-measured object can be improved.

1 is a block diagram showing a schematic configuration of a displacement sensor according to a first embodiment; FIG. FIG. 3 is a functional block diagram showing the internal configuration of a control unit that performs first interpolation processing; The figure which shows the correlation data in the temperature T1. The figure which shows the correlation data in the temperature T2. Fig. 3 shows correlation data after interpolation processing; 4 is a flowchart showing a processing procedure of a first interpolation process; FIG. 5 is a functional block diagram showing the internal configuration of a control unit that performs a second interpolation process; 6A and 6B are diagrams for explaining an outline of a second interpolation process performed by an interpolation processing unit in FIG. 5; FIG. The figure following FIG. 6A. 6 is a flowchart showing a processing procedure of a second interpolation process; FIG. 10 is a functional block diagram showing the internal configuration of a control unit that performs a third interpolation process; FIG. 9 is a diagram for explaining an overview of second interpolation processing performed by the interpolation processing unit in FIG. 8 ; The figure following FIG. 9A. 10 is a flowchart showing a processing procedure of third interpolation processing; 4 is a flowchart showing an example of processing operations of a control unit according to the first embodiment;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.

(First embodiment)
FIG. 1 is a block diagram showing a schematic configuration of a displacement sensor 1 according to the first embodiment. The displacement sensor 1 of FIG. 1 includes a coil 2, an oscillator 3, a rectifier 4, an A/D converter 5, a control section (displacement signal generation section) 6, a D/A converter 7, an output amplifier 8, A temperature measuring instrument 9 is provided.

The oscillator 3 is composed of, for example, a self-excited oscillation circuit. A self-excited oscillating circuit can simplify the circuit configuration compared to a separately-excited oscillating circuit, and can reduce the mounting area and the cost of parts. In addition, since the resonance of the coil is used, there is an advantage that the change in the oscillation signal level can be increased with the change in the distance. Although the specific circuit configuration of the self-excited oscillator circuit is not particularly limited, for example, a Colpitts oscillator circuit can be applied.

The oscillator 3 incorporates a resonance circuit made up of the coil 2 and a capacitor (not shown). An alternating current having a resonance frequency flows through the coil 2 . Therefore, a magnetic flux corresponding to the alternating current is generated from the coil 2 , and this magnetic flux generates an eddy current in the object to be measured placed near the coil 2 . When an eddy current is generated in the object to be measured, the impedance of the coil 2 changes due to its influence, and the signal level of the oscillation signal of the oscillation circuit also changes. In this way, the coil 2 generates an alternating magnetic field by supplying an alternating current, and generates an output corresponding to the eddy current induced in the object to be measured according to the displacement of the position of the object to be measured.

If the object to be measured is an insulator, no eddy current is generated. Therefore, the object to be measured for which the displacement sensor 1 of FIG. 1 can detect the displacement, ie, the gap, is limited to a conductor. The object to be measured may be any conductor as long as it is a non-magnetic substance or a magnetic substance.

Rectifier 4 rectifies the oscillation signal of oscillator 3, that is, the output of coil 2, and converts it into a DC signal. A/D converter 5 converts the DC signal output from rectifier 4 into a digital signal. A temperature measuring instrument 9 measures the actual temperature around the coil 2 . When the displacement sensor 1 of FIG. 1 is used to measure the position of an engine valve, for example, the temperature around the coil 2 may reach a high temperature exceeding 100.degree. As described above, the impedance of the coil 2 changes depending on the temperature, and the output signal of the displacement sensor 1 also changes. Therefore, it is desirable to measure the temperature at a location as close as possible to the coil 2 under the operating environment of the displacement sensor 1 . The temperature measuring instrument 9 may measure the temperature of the coil 2 itself or the temperature in the vicinity of the coil 2 .

The control unit 6 calculates the correlation between the output of the coil 2 when the temperature around the coil 2 is a predetermined value and the corrected displacement signal indicating the displacement of the position of the object to be measured, which is obtained from the output of the coil 2 and corrected for the temperature. is used to output a corrected displacement signal corresponding to the actual temperature and the output of the coil 2 as a displacement signal indicating the displacement of the position of the object to be measured. More specifically, the control unit 6 determines the correlation between the output of the coil 2 at each of a plurality of temperatures and the corrected displacement signal indicating the displacement of the position of the object to be measured corrected for temperature, which is obtained from the output of the coil 2. , a corrected displacement signal corresponding to the actual temperature measured by the temperature measuring instrument 9 and the output of the coil 2 is output as a displacement signal indicating the positional displacement of the object to be measured. The control unit 6 generates displacement signals by software processing, and for example, reads and executes a program stored in the program storage unit 10 to perform the above-described signal processing and generate displacement signals. Thus, more specifically, the control unit 6 can be configured by an MCU (Micro Control Unit) or an MPU (Micro Processing Unit) that executes the above program.

A correlation storage unit 11 and an interpolation processing unit 12 are built in or connected to the control unit 6 . Note that FIG. 1 shows an example in which the correlation storage unit 11 and the interpolation processing unit 12 are built in the control unit 6, but at least one of the correlation storage unit 11 and the interpolation processing unit 12 is may be provided separately. The correlation storage unit 11 stores correlation data between the digital signal corresponding to the output of the rectifier 4 and the corrected displacement signal for each of a plurality of temperatures of the coil 2 . In storing the correlation data in the correlation storage unit 11, the coil 2 is set to a certain temperature, and the gap from the object to be measured is changed in a plurality of ways to correspond to the output signal of the rectifier 4 at each gap. A digital signal is detected and correlation data between the output of the coil 2, that is, the output signal of the rectifier 4 and the correction displacement signal is generated so that the correction displacement signal at each gap varies linearly with respect to the gap. Such correlation data is generated for each temperature by changing the temperature of the coil 2 in a plurality of ways, and stored in the correlation storage unit 11 .

Instead of storing the correlation data in the correlation storage unit 11, the control unit 6 provides a function expression representing the correlation, gives the function expression an input parameter corresponding to the output of the rectifier 4, and performs arithmetic processing. may be performed to obtain the corrected displacement signal.

The interpolation processor 12 interpolates a corrected displacement signal corresponding to the actual temperature measured by the temperature measuring instrument 9 . That is, the interpolation processing section 12 interpolates the correlation data stored in the correlation storage section 11 based on the actual temperature measured by the temperature measuring instrument 9 . The interpolation processing unit 12 may generate a correlation at an intermediate temperature between the two temperatures from the correlation between the output of the coil and the corrected displacement signal at at least two temperatures different from each other. As will be described later, a plurality of types of interpolation processing are conceivable for the interpolation processing performed by the interpolation processing unit 12 . The correlation data newly generated by interpolation processing performed by the interpolation processing unit 12 is stored in the correlation storage unit 11, for example. Alternatively, the correlation data newly generated by the interpolation processing unit 12 may be stored separately from the correlation storage unit 11 .

The control unit 6 outputs the corrected displacement signal interpolated by the interpolation processing unit as a displacement signal. More specifically, the control unit 6 responds to the output signal of the rectifier 4 at the actual temperature measured by the temperature measuring device 9 based on the correlation data newly generated by the interpolation processing unit 12. Generate a corrected displacement signal. If the correlation data does not contain data corresponding to the output signal of the rectifier 4, data close to the output signal of the rectifier 4 is used to generate a corrected displacement signal through interpolation processing.

Next, the interpolation processing performed by the control unit 6 will be described in detail. A plurality of types of interpolation processing can be considered for the interpolation processing performed by the interpolation processing unit 12 in the control unit 6 . Below, representative first to third interpolation processes will be described in order. The interpolation processing unit 12 may employ any one of the first to third interpolation processes described below.

FIG. 2 is a functional block diagram showing the internal configuration of the control section 6 that performs the first interpolation processing. The control unit 6 in FIG. 2 has the correlation storage unit 11, the interpolation processing unit 12, and the data output unit 14 described above. The data output unit 14 outputs a corrected displacement signal generated based on the correlation data interpolated by the interpolation processing unit 12 as a displacement signal.

3A, 3B, and 3C are diagrams for explaining the outline of the first interpolation processing performed by the interpolation processing section 12 of FIG. 2. FIG. 3A and 3B show an example of correlation data stored in advance in the correlation storage unit 11. FIG. 3A shows correlation data cor1 at temperature T1, and FIG. 3B shows correlation data cor2 at temperature T2. is shown.

As shown in FIG. 3C, the interpolation processing unit 12 proportionally distributes the correlation data cor1 in FIG. 3A and the correlation data cor2 in FIG. 3B based on the temperature around the coil 2 measured by the temperature measuring instrument 9. Then, interpolation processing is performed to generate new correlation data cor3.

The control unit 6 generates a correction displacement signal corresponding to the output signal of the rectifier 4 at the temperature around the coil 2 measured by the temperature measuring instrument 9 based on the correlation data cor3.

FIG. 4 is a flow chart showing the procedure of the first interpolation process. First, correlation data between the output of the rectifier 4 and the corrected displacement signal is stored in the correlation storage unit 11 for at least two temperatures (step S1). Below, as shown in FIGS. 3A and 3B, it is assumed that two types of correlation data cor1 and cor2 regarding the first temperature and the second temperature, which are different from each other, are stored in the correlation storage unit 11. FIG. Also, hereinafter, the correlation data at the first temperature will be referred to as first correlation data cor1, and the correlation data at the second temperature will be referred to as second correlation data cor2.

Next, based on the first correlation data cor1 at the first temperature, a corrected displacement signal corresponding to the output signal of the rectifier 4 is acquired, and based on the second correlation data cor2 at the second temperature, the rectifier A corrected displacement signal corresponding to the output signal of 4 is acquired (step S2).

Here, when data corresponding to the output signal of the rectifier 4 does not exist in either the first correlation data cor1 or the second correlation data cor2, interpolation processing is performed using data near the output signal of the rectifier 4, A corrected displacement signal may be generated.

Next, using the corrected displacement signal obtained using the correlation data cor1 at the first temperature and the corrected displacement signal obtained using the second correlation data cor2 at the second temperature, a new displacement signal is obtained by interpolation processing. Correlation data cor3 is generated, and based on this correlation data cor3, a correction displacement signal corresponding to the actual temperature measured by the temperature measuring instrument 9 is generated (step S3). For example, if the temperature measured by the temperature measuring instrument 9 is an intermediate temperature between the first temperature and the second temperature, the corrected displacement signal obtained based on the first correlation data cor1 and the second correlation data cor2 The average value of the corrected displacement signal acquired by the temperature measurement device 9 is used as the corrected displacement signal corresponding to the output signal of the rectifier 4 at the temperature measured by the temperature measuring instrument 9 .

FIG. 5 is a functional block diagram showing the internal configuration of the control section 6 that performs the second interpolation processing. The control unit 6 of FIG. 5 includes a correlation storage unit 11, an interpolation processing unit 12, and a data output unit 14. The correlation storage unit 11 includes a first correlation storage unit 11a and a second correlation storage unit 11a. and a portion 11b. The first correlation storage section 11a stores a first correlation between the output of the rectifier 4 at the first temperature and the corrected displacement signal. The second correlation storage section 11b stores a second correlation between the output of the rectifier 4 and the corrected displacement signal at a second temperature different from the first temperature.

The interpolation processing unit 12 in FIG. 5 performs interpolation processing of the first correlation to generate the second correlation while the displacement sensor 1 performs measurement using the first correlation. Stored in the relationship storage unit 11b. The controller 6 generates a corrected displacement signal based on the second correlation when the actual temperature measured by the temperature measuring instrument 9 changes to the second temperature.

6A and 6B are diagrams for explaining the outline of the second interpolation processing performed by the interpolation processing section 12 of FIG. 5. FIG. The solid line in FIG. 6A is the correlation data cor4 at the predetermined temperature T3 pre-stored in the first correlation storage unit 11a. The dashed lines in FIG. 6A are the correlation data cor5 and cor6 at temperatures slightly shifted from the predetermined temperature T3 during the displacement measurement by the displacement sensor 1 . The solid line in FIG. 6B is the correlation data cor6 after the temperature change, and the broken line in FIG. 6B is the original correlation data cor4.

FIG. 7 is a flow chart showing the procedure of the second interpolation process. First, the correlation data cor4 between the output of the rectifier 4 and the correction displacement signal at a certain predetermined temperature is stored in the correlation storage unit 11 (step S11). Using this correlation data, displacement measurement processing by the displacement sensor 1 is started (step S12). While this process is continuously executed, the correlation data cor4 stored in the correlation storage unit 11 is used to interpolate the correlation data cor5 and cor6 at temperatures slightly shifted from the predetermined temperature. (step S13). When the new correlation data cor5 and cor6 are completed, the data are stored in the correlation storage unit 11 or another storage unit (step S14).

After that, when the actual temperature measured by the temperature measuring device 9 reaches the temperature of the correlation data cor5 or cor6 generated in steps S13 and S14, the control unit 6 uses this correlation data to convert the output signal of the rectifier 4. Obtain the corresponding corrected displacement signal. FIG. 6B shows an example in which the temperature corresponds to the correlation data cor6.

FIG. 8 is a functional block diagram showing the internal configuration of the control section 6 that performs the third interpolation processing. The control unit 6 of FIG. 8 has a configuration similar to that of the control unit 6 of FIG. The difference from the control unit 6 in FIG. 5 is that one type of correlation data is stored in the 2-correlation storage unit 11b.

9A and 9B are diagrams for explaining the outline of the third interpolation processing performed by the interpolation processing section 12 of FIG. 8. FIG. The solid line in FIG. 9A is the correlation data cor7 at the predetermined temperature T4 pre-stored in the first correlation storage unit 11a. The dashed line in FIG. 9A is the correlation data cor8 obtained by performing the third interpolation processing on the correlation data cor7. The solid line in FIG. 9B is the correlation data cor8, and the dashed line is the original correlation data cor7.

FIG. 10 is a flow chart showing the procedure of the third interpolation process. First, the correlation data cor7 between the output of the rectifier 4 and the corrected displacement signal at a certain predetermined temperature is stored in the first correlation storage unit 11a (step S21). Using this correlation data cor7, displacement measurement processing by the displacement sensor 1 is started (step S22). If the actual temperature measured by the temperature measuring instrument 9 changes while this process is continuously executed, the correlation data cor7 stored in the first correlation storage unit 11a is used to perform the interpolation process. Then, the correlation data cor8 at the actual temperature measured by the temperature measuring instrument 9 is generated (step S23). When the new correlation data cor8 is completed, this correlation data cor8 is stored in the second correlation storage section 11b (step S24). After that, the controller 6 uses the replaced correlation data to generate a corrected displacement signal corresponding to the output of the rectifier 4 . Also, the correlation data cor7 stored in the first correlation storage unit 11a is deleted, the correlation data stored in the second correlation storage unit 11b is copied to the first correlation storage unit 11a, and the above-described You may repeat the process after step S21 which carried out.

When performing the first to third interpolation processing, the interpolation processing unit 12 performs the interpolation processing so that the correction displacement signal changes linearly with respect to changes in the output of the coil 2, that is, the output of the rectifier 4. is desirable. Thereby, a correction displacement signal that varies linearly with respect to the output of the rectifier 4 can be generated.

FIG. 11 is a flow chart showing an example of the processing operation of the control section 6 according to the first embodiment. When the coil 2 of the displacement sensor 1 is arranged near the object to be measured, the impedance of the coil 2 changes, the signal level of the oscillation signal of the oscillator 3 changes, and accordingly the DC signal output from the rectifier 4 changes. The signal level also changes. This DC signal is converted into a digital signal by the A/D converter 5 and then inputted to the control section 6 (step S31).

Before and after the process of step S31, the control unit 6 acquires the temperature around the coil 2 measured by the temperature measuring instrument 9 (step S32). Next, based on the temperature around the coil 2 and the digital signal output from the rectifier 4 and digitally converted by the A/D converter 5, the control unit 6 causes the interpolation processing unit 12 to perform the above-described first to first A corrected displacement signal is generated using the correlation data generated by performing any one of the three interpolation processes (step S33).

In the displacement sensor 1, the components other than the coil 2 are mounted on a common substrate, and only the coil 2 is often placed apart from this substrate. In this case, the temperature difference between the temperature around the coil 2 and the temperature of the substrate may increase. In particular, when the temperature of the object to be measured exceeds several hundred degrees Celsius, such as when detecting the position of an engine valve, the temperature difference between the temperature around the coil 2 and the temperature around the substrate is large. Prone. As described above, the impedance of the coil 2 changes depending on the temperature of the coil 2, but the temperature of the substrate also changes the electrical characteristics of each circuit element in the substrate, affecting the signal level of the correction displacement signal.

Therefore, if there is a possibility that the temperature around the coil 2 and the temperature around the substrate are different, the temperature around the substrate is measured separately from the temperature measuring instrument 9 that measures the temperature around the coil 2. A substrate temperature measuring instrument 13 may be provided.

In this case, the control unit 6 controls the coil temperature measured by the temperature measuring device 9 and the substrate temperature measuring device 13 based on the correlation between the output of the rectifier 4 and the corrected displacement signal at a plurality of temperatures. A corrected displacement signal corresponding to the temperature of the substrate is generated.

As a result, the temperature around the coil 2 and the temperature around the substrate can be taken into account to generate a correction displacement signal for the displacement of the object to be measured. Even if the displacement of the measurement object changes, the linearity of the displacement signal with respect to the displacement can be further improved.

As described above, in this embodiment, based on the correlation between the output of the rectifier 4 and the corrected displacement signal at a plurality of temperatures, the output signal of the rectifier 4 at the actual temperature measured by the temperature measuring instrument 9 is corrected. Since the correction displacement signal is generated, the actual temperature measured by the temperature measuring instrument 9 is taken into consideration, and the correction displacement signal can be generated with high accuracy by software processing. In the present embodiment, correlations for a large number of temperatures are obtained by interpolating the correlations according to the actual temperatures measured by the temperature measuring instrument 9 using the correlations for at least one type of temperature. No need to prepare in advance. Therefore, displacement signals can be generated over a wide temperature range.

In addition, since the control unit 6 can be configured with a single MCU or MPU, the hardware configuration can be simplified and the parts cost can be reduced. Furthermore, the processing operation of the control unit 6 can be changed in various ways by improving the program, and the processing for improving the linearity of the displacement signal with respect to the displacement of the object to be measured can be performed relatively easily without changing the hardware. It can be carried out. It is desirable that the program storage unit 10 is composed of an electrically rewritable flash memory, an EEPROM, or the like so that the programs can be easily replaced. In particular, when the displacement sensor 1 according to the present embodiment is used at high temperatures, it is more desirable to construct the correlation storage unit 11 and the program storage unit 10 using a non-volatile memory with high data retention performance even at high temperatures. .

Aspects of the present invention are not limited to the individual embodiments described above, but include various modifications that can be conceived by those skilled in the art, and the effects of the present invention are not limited to the above-described contents. That is, various additions, changes, and partial deletions are possible without departing from the conceptual idea and spirit of the present invention derived from the content defined in the claims and equivalents thereof.

1 Displacement Sensor 2 Coil 3 Oscillator 4 Rectifier 5 A/D Converter 6 Control Unit 7 D/A Converter 8 Output Amplifier 9 Temperature Measuring Instrument 10 Program Storage Unit 11 Correlation Storage Unit 11b second correlation storage unit, 12 interpolation processing unit, 13 substrate temperature measuring instrument

Claims (6)

a coil that generates an alternating magnetic field by supplying an alternating current and generates an output corresponding to an eddy current induced in the object to be measured according to a displacement of the position of the object;
a temperature measuring instrument for measuring the actual temperature around the coil;
Using the correlation between the output of the coil when the temperature around the coil is a predetermined value and a corrected displacement signal indicating the displacement of the position of the object to be measured that has undergone temperature correction and is obtained from the output of the coil, a displacement signal generator that outputs a corrected displacement signal corresponding to the actual temperature and the output of the coil as a displacement signal indicating the displacement of the position of the object to be measured;
an interpolation processing unit that interpolates a corrected displacement signal corresponding to the actual temperature measured by the temperature measuring instrument based on the correlation between the output of the coil and the corrected displacement signal at at least one temperature;
a first correlation storage that stores a first correlation between the output of the coil at a first temperature and the corrected displacement signal;
a second correlation storage unit that stores a second correlation between the output of the coil and the corrected displacement signal at a second temperature different from the first temperature;
The interpolation processing unit generates the second correlation by interpolation processing of the first correlation while measuring the displacement of the position of the object to be measured using the first correlation. and store it in the second correlation storage unit,
The displacement signal generating section outputs the corrected displacement signal interpolated by the interpolation processing section as the displacement signal, and when the temperature measured by the temperature measuring instrument changes to the second temperature, the second A displacement sensor that generates the corrected displacement signal based on two correlations. a coil that generates an alternating magnetic field by supplying an alternating current and generates an output corresponding to an eddy current induced in the object to be measured according to a displacement of the position of the object;
a temperature measuring instrument for measuring the actual temperature around the coil;
Using the correlation between the output of the coil when the temperature around the coil is a predetermined value and a corrected displacement signal indicating the displacement of the position of the object to be measured that has undergone temperature correction and is obtained from the output of the coil, a displacement signal generator that outputs a corrected displacement signal corresponding to the actual temperature and the output of the coil as a displacement signal indicating the displacement of the position of the object to be measured;
an interpolation processing unit that interpolates a corrected displacement signal corresponding to the actual temperature measured by the temperature measuring instrument based on the correlation between the output of the coil and the corrected displacement signal at at least one temperature;
a first correlation storage that stores a first correlation between the output of the coil at a first temperature and the corrected displacement signal;
a second correlation storage unit that stores a second correlation between the output of the coil and the corrected displacement signal at a second temperature different from the first temperature;
The displacement signal generation unit outputs the corrected displacement signal interpolated by the interpolation processing unit as the displacement signal, and uses the first correlation to measure the displacement of the position of the object to be measured. When the temperature measured by the temperature measuring instrument changes from the first temperature to the second temperature during the operation, the second correlation is generated by interpolation processing of the first correlation, and the second correlation is generated. Displacement sensor stored in the correlation storage unit. 3. The interpolation processing unit according to claim 1, wherein the interpolation processing unit interpolates the correlation to generate a new correlation such that the corrected displacement signal changes linearly with respect to changes in the output of the coil. Displacement sensor. 3. The interpolation processing unit generates the correlation at an intermediate temperature between the two temperatures from the correlation between the output of the coil and the corrected displacement signal at at least two temperatures different from each other. 4. The displacement sensor according to any one of 3. a substrate on which the displacement signal generator is mounted;
a substrate temperature measuring instrument for measuring the temperature of the substrate,
2. The interpolation processing unit interpolates the correlation based on the temperature around the coil measured by the temperature measuring instrument and the temperature of the substrate measured by the substrate temperature measuring instrument. 5. The displacement sensor according to any one of 4. a self-excited oscillation circuit that generates the alternating current by performing an oscillation operation using the impedance of the coil and outputs an oscillation signal;
6. The displacement sensor according to claim 1, wherein the oscillation level of said self-excited oscillator circuit changes under the influence of changes in impedance of said coil caused by eddy currents generated in said object to be measured.

Images