JP2020063963A - Displacement sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the linearity of a displacement signal with respect to a displacement of an object to be measured. SOLUTION: A coil 2 generates an AC magnetic field by supplying an AC current, and generates an output according to an eddy current induced in the object to be measured according to the displacement of the position of the object to be measured. The temperature measuring device 9 that measures the actual temperature around the coil 2, the output of the coil 2 when the temperature around the coil 2 is a predetermined value, and the position of the temperature-corrected object to be measured obtained from the output of the coil 2. A displacement signal generator 6 that outputs 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 by using the correlation with the corrected displacement signal indicating the displacement. , Equipped with. [Selection diagram] Fig. 1

Description

  The present invention relates to a displacement sensor that detects a distance from a measurement object, that is, a gap without contact.

  A displacement sensor using a coil includes an oscillator that causes an alternating current to flow through the coil, and a circuit that detects a signal change due to a change in the impedance of the coil. The oscillation signal of the oscillator is converted into a DC signal by the rectifier, and then the linearizer generates a signal that linearly changes according to the gap with the DUT (see Patent Documents 1 and 2).

  It is known that the impedance of the coil changes with temperature. Therefore, in Patent Document 1, the amplitude level of the oscillation signal output from the oscillator having the coil is corrected by the temperature. Further, in Patent Document 2, the output of the linearizer is corrected with a correction value according to the temperature.

JP, 2005-137888, A JP 8-272044A

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

  In addition, since the signal frequency is high on the front side of the rectifier, it is easily affected by stray capacitance.If a temperature correction circuit is provided on the front side of the rectifier, heat is likely to occur due to the high signal frequency, and the temperature correction accuracy is improved. May have adverse effects.

  On the other hand, in Patent Document 2, the output voltage of the R-V converter is added to the output voltage of the linearizer to perform the correction process. However, in the simple addition process, the correction process is performed only at the specific displacement to which the addition process is performed. This cannot be done, and the input / output characteristics of the linearizer over a wide range cannot be linearized.

  Further, when temperature correction is performed on the output of the linearizer as in Patent Document 2, a signal that has not been temperature corrected is input to the linearizer. In particular, in the high frequency range, the signal from the rectifier circuit is greatly attenuated. Therefore, even if temperature correction is performed on the output of the linearizer to which such an attenuation signal is input, the temperature correction is sufficient to compensate for the signal attenuation. May not be possible.

  Further, both Patent Documents 1 and 2 have in mind that the correction process is performed by a combination of electric parts, and the electrical characteristics are likely to change due to environmental conditions such as temperature and deterioration over time, and a failure is likely to occur. There is a problem of poor sex.

  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, while reducing the member cost and minimizing the temperature dependency.

In order to solve the above problems, in one embodiment of the present invention, an alternating magnetic field is generated by supplying an alternating current, and an eddy current is induced in the measured object according to displacement of the position of the measured object. A coil that produces an output according to
A temperature measuring device for measuring the actual temperature around the coil,
By using the correlation between the output of the coil when the temperature around the coil has a predetermined value, and the corrected displacement signal indicating the displacement of the position of the measured object that has been temperature-corrected obtained from the output of the coil, There is provided a displacement sensor including a displacement signal generation unit that outputs a corrected displacement signal corresponding to an actual temperature and an output of the coil as a displacement signal indicating displacement of a position of an object to be measured.

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

  The interpolation processing unit may interpolate the correlation so as to generate a new correlation so that the corrected displacement signal changes linearly with respect to a change in the output of the coil.

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

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

A first correlation storage unit that stores a first correlation between the output of the coil and the corrected displacement signal at a first temperature;
A second correlation storage unit that stores a second correlation between the output of the coil and the correction displacement signal at a second temperature different from the first temperature,
The interpolation processing unit generates the second correlation by the interpolation processing of the first correlation while the displacement sensor is performing measurement using the first correlation, and generates the second correlation. Stored in the relation store,
The displacement signal generation unit 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 unit that stores a first correlation between the output of the coil and the corrected displacement signal at a first temperature;
A second correlation storage unit that stores a second correlation between the output of the coil and the correction displacement signal at a second temperature different from the first temperature,
When the temperature measured by the temperature measuring device changes from the first temperature to the second temperature while the displacement sensor is measuring using the first correlation, The second correlation may be generated by the interpolation processing of the first correlation and stored in the second correlation storage unit.

While generating an alternating current by performing an oscillating operation using the impedance of the coil, and having a self-excited oscillation circuit that outputs an oscillation signal,
The oscillation level of the self-excited oscillation circuit may change under the influence of a change in impedance of the coil due to an eddy current generated in the DUT.

  According to the present invention, it is possible to reduce the member cost and improve the linearity of the displacement signal with respect to the displacement of the measured object.

FIG. 3 is a block diagram showing a schematic configuration of a displacement sensor according to the first embodiment. The functional block diagram which shows the internal structure of the control part which performs a 1st interpolation process. The figure which shows the correlation data in temperature T1. The figure which shows the correlation data in temperature T2. The correlation data after interpolation processing are shown. The flowchart which shows the process sequence of a 1st interpolation process. The functional block diagram which shows the internal structure of the control part which performs a 2nd interpolation process. The figure explaining the outline | summary of the 2nd interpolation processing which the interpolation processing part of FIG. The figure following FIG. 6A. The flowchart which shows the process sequence of a 2nd interpolation process. The functional block diagram which shows the internal structure of the control part which performs a 3rd interpolation process. The figure explaining the outline | summary of the 2nd interpolation process which the interpolation process part of FIG. The figure following FIG. 9A. The flowchart which shows the process sequence of a 3rd interpolation process. 3 is a flowchart showing an example of processing operation of the control unit according to the first embodiment.

  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 unit (displacement signal generation unit) 6, a D / A converter 7, an output amplifier 8, The temperature measuring instrument 9 is provided.

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

  The oscillator 3 includes a resonance circuit including 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 the magnetic flux generates an eddy current in the object to be measured arranged 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 the 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 produces an output according to the eddy current induced in the measured object according to the displacement of the position of the measured object.

  When the object to be measured is an insulator, no eddy current is generated, and therefore the object to be measured whose displacement, that is, the gap can be detected by the displacement sensor 1 of FIG. 1 is limited to a conductor. The object to be measured may be a conductor and may be a non-magnetic material or a magnetic material.

  The rectifier 4 rectifies the oscillation signal of the oscillator 3, that is, the output of the coil 2 and converts it into a DC signal. The A / D converter 5 converts the DC signal output from the rectifier 4 into a digital signal. The temperature measuring device 9 measures the actual temperature around the coil 2. When the displacement sensor 1 of FIG. 1 is used, for example, to measure the position of a valve of an engine, the temperature around the coil 2 may be as high as 100 ° C. or higher. 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 place as close as possible to the coil 2 under the usage environment of the displacement sensor 1. The temperature measuring device 9 may measure the temperature of the coil 2 itself or the temperature in the vicinity of the coil 2.

  The controller 6 correlates 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 temperature-corrected position of the measured object obtained from the output of the coil 2. Then, the correction displacement signal corresponding to the actual temperature and the output of the coil 2 is output as the displacement signal indicating the displacement of the position of the measured object. More specifically, the control unit 6 correlates the output of the coil 2 at each of the plurality of temperatures and the corrected displacement signal indicating the displacement of the temperature-corrected position of the measured object obtained from the output of the coil 2. Based on the above, the correction displacement signal corresponding to the actual temperature measured by the temperature measuring device 9 and the output of the coil 2 is output as the displacement signal indicating the displacement of the position of the measured object. The control unit 6 generates a displacement signal by software processing. For example, by reading and executing a program stored in the program storage unit 10, the control unit 6 performs the above-described signal processing to generate a displacement signal. 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-described program.

  The correlation storage unit 11 and the interpolation processing unit 12 are built in or connected to the control unit 6. Although FIG. 1 shows an example in which the correlation storage unit 11 and the interpolation processing unit 12 are incorporated in the control unit 6, at least one of the correlation storage unit 11 and the interpolation processing unit 12 is connected to the control unit 6. May be provided separately. The correlation storage unit 11 stores the correlation data between the digital signal corresponding to the output of the rectifier 4 and the corrected displacement signal for each of the plurality of temperatures of the coil 2. When the correlation data is stored in the correlation storage unit 11, a plurality of gaps with the object to be measured are changed in a state in which the coil 2 is set to a certain temperature and the output signal of the rectifier 4 in each gap is corresponded. The digital signal is detected, and the correlation data between the output of the coil 2, that is, the output signal of the rectifier 4 and the corrected displacement signal is generated so that the corrected displacement signal in each gap changes linearly with respect to the gap. Such correlation data is generated for each temperature by changing the temperature of the coil 2 in multiple 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 functional expression representing the correlation and gives an input parameter corresponding to the output of the rectifier 4 to this functional expression to perform an arithmetic process. May be performed to obtain the corrected displacement signal.

  The interpolation processing unit 12 interpolates the corrected displacement signal corresponding to the actual temperature measured by the temperature measuring device 9. That is, the interpolation processing unit 12 interpolates the correlation data stored in the correlation storage unit 11 based on the actual temperature measured by the temperature measuring device 9. The interpolation processing unit 12 may generate the correlation at the intermediate temperature between the two temperatures from the correlation between the output of the coil and the correction displacement signal at at least two different temperatures. As will be described later, there are a plurality of possible interpolation processes performed by the interpolation processing unit 12. The correlation data newly generated by the interpolation processing unit 12 performing the interpolation processing is stored in, for example, the correlation storage unit 11. 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 corresponds 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 by the interpolation processing. Generate a corrected displacement signal. If the correlation data does not include the data corresponding to the output signal of the rectifier 4, the correction displacement signal is generated by the interpolation process using the data close to the output signal of the rectifier 4.

  Next, the interpolation process performed by the control unit 6 will be described in detail. There are a plurality of possible interpolation processes performed by the interpolation processing unit 12 in the control unit 6. Below, typical 1st-3rd interpolation processing is demonstrated in order. The interpolation processing unit 12 may employ any of the following first to third interpolation processing.

  FIG. 2 is a functional block diagram showing the internal configuration of the control unit 6 that performs the first interpolation processing. The control unit 6 in FIG. 2 includes the correlation storage unit 11, the interpolation processing unit 12, and the data output unit 14 described above. The data output unit 14 outputs the 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 unit 12 in FIG. 3A and 3B show an example of the correlation data stored in advance in the correlation storage unit 11. FIG. 3A shows the correlation data cor1 at the temperature T1, and FIG. 3B shows the correlation data cor2 at the temperature T2. Is shown.

  As shown in FIG. 3C, the interpolation processing unit 12 proportionally distributes the correlation data cor1 of FIG. 3A and the correlation data cor2 of FIG. 3B based on the temperature around the coil 2 measured by the temperature measuring device 9. 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 device 9 based on the correlation data cor3.

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

  Next, the correction displacement signal corresponding to the output signal of the rectifier 4 is acquired based on the first correlation data cor1 at the first temperature, and the rectifier based on the second correlation data cor2 at the second temperature. The corrected displacement signal corresponding to the output signal of No. 4 is acquired (step S2).

  Here, when the 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, the interpolation processing is performed using the data in the vicinity of the output signal of the rectifier 4, A corrected displacement signal may be generated.

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

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

  The interpolation processing unit 12 of FIG. 5 performs the interpolation processing of the first correlation to generate the second correlation while the displacement sensor 1 is performing the measurement using the first correlation to generate the second correlation. It is stored in the relationship storage unit 11b. When the actual temperature measured by the temperature measuring device 9 changes to the second temperature, the control unit 6 generates a corrected displacement signal based on the second correlation.

  6A and 6B are diagrams for explaining the outline of the second interpolation processing performed by the interpolation processing unit 12 in FIG. The solid line in FIG. 6A is the correlation data cor4 at the predetermined temperature T3 stored in advance in the first correlation storage unit 11a. The broken line in FIG. 6A is the correlation data cor5 and cor6 at a temperature slightly deviated 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 flowchart showing the processing procedure of the second interpolation processing. First, the correlation data cor4 between the output of the rectifier 4 and a corrected displacement signal at a certain predetermined temperature is stored in the correlation storage unit 11 (step S11). The displacement measurement process by the displacement sensor 1 is started using this correlation data (step S12). During the continuous execution of this process, the correlation data cor5 stored in the correlation storage unit 11 is used to interpolate the correlation data cor5 and cor6 at a temperature slightly deviated from the predetermined temperature. (Step S13). When the new correlation data cor5 and cor6 are completed, the data is 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 the correlation data to output the output signal of the rectifier 4. Obtain the corresponding corrected displacement signal. FIG. 6B shows an example in which the temperature reaches the temperature corresponding to the correlation data cor6.

  FIG. 8 is a functional block diagram showing an internal configuration of the control unit 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. 5, except that the correction displacement signal read from the first correlation storage unit 11a is input to the data output unit 14. The difference from the control unit 6 of FIG. 5 is that one type of correlation data is stored in the two-correlation storage unit 11b.

  9A and 9B are diagrams for explaining the outline of the third interpolation processing performed by the interpolation processing unit 12 in FIG. The solid line in FIG. 9A is the correlation data cor7 at the predetermined temperature T4 stored in advance in the first correlation storage unit 11a. The broken 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 broken line is the original correlation data cor7.

  FIG. 10 is a flowchart showing the processing procedure of the third interpolation processing. 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, the displacement measurement process by the displacement sensor 1 is started (step S22). If the actual temperature measured by the temperature measuring device 9 changes during the continuous execution of this processing, the correlation data cor7 stored in the first correlation storage unit 11a is used for interpolation processing. Then, the correlation data cor8 at the actual temperature measured by the temperature measuring device 9 is generated (step S23). When the new correlation data cor8 is completed, the correlation data cor8 is stored in the second correlation storage unit 11b (step S24). After that, the control unit 6 uses the swapped correlation data to generate a corrected displacement signal corresponding to the output of the rectifier 4. Further, the correlation data cor7 stored in the first correlation storage unit 11a is deleted, and the correlation data stored in the second correlation storage unit 11b is copied to the first correlation storage unit 11a. You may repeat the process after step S21 which did.

  When performing the first to third interpolation processes, the interpolation processing unit 12 performs the interpolation process so that the corrected displacement signal changes linearly with respect to the change in the output of the coil 2, that is, the output of the rectifier 4. Is desirable. This makes it possible to generate a corrected displacement signal that changes linearly with respect to the output of the rectifier 4.

  FIG. 11 is a flowchart showing an example of the processing operation of the control unit 6 according to the first embodiment. When the coil 2 of the displacement sensor 1 is arranged in the vicinity of 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 input to the control unit 6 (step S31).

  The control unit 6 acquires the temperature around the coil 2 measured by the temperature measuring device 9 before and after the process of step S31 (step S32). Next, the control unit 6 controls the interpolation processor 12 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. A corrected displacement signal is generated using the correlation data generated by performing any of the three interpolation processes (step S33).

  In the displacement sensor 1, components other than the coil 2 are often mounted on a common substrate, and only the coil 2 is often arranged at a position 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 position of the valve of the engine is detected and the temperature of the object to be measured reaches a high temperature exceeding several hundreds of degrees Celsius, 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 electrical characteristics of each circuit element in the substrate also change depending on the temperature of the substrate, which affects the signal level of the correction displacement signal.

  Therefore, when 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 device 9 that measures the temperature around the coil 2. A substrate temperature measuring device 13 may be provided.

  In this case, the control unit 6 measures 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. And generating a corrected displacement signal corresponding to the temperature of the substrate.

  Thus, the temperature around the coil 2 and the temperature around the substrate can be taken into consideration to generate the correction displacement signal for the displacement of the object to be measured, and even if the temperature of the coil 2 or the substrate changes, 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 the present embodiment, the output signal of the rectifier 4 at the actual temperature measured by the temperature measuring device 9 is supported based on the correlation between the output of the rectifier 4 at a plurality of temperatures and the corrected displacement signal. Since the corrected displacement signal is generated, it is possible to accurately generate the corrected displacement signal by software processing in consideration of the actual temperature measured by the temperature measuring device 9. In the present embodiment, since the correlation according to the actual temperature measured by the temperature measuring device 9 is obtained by the interpolation processing by using the correlation for at least one kind of temperature, the correlation for many temperatures is calculated. There is no need to prepare in advance. Therefore, the displacement signal can be generated in a wide temperature range.

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

  The 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 can be made without departing from the conceptual idea and spirit of the present invention derived from the contents defined in the claims and the 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 device, 10 program storage unit, 11 correlation storage unit, 11b Second correlation storage unit, 12 interpolation processing unit, 13 substrate temperature measuring device

Claims (8)

A coil that generates an alternating magnetic field by supplying an alternating current and that generates an output according to an eddy current induced in the object to be measured according to the displacement of the position of the object to be measured,
A temperature measuring device for measuring the actual temperature around the coil,
By using the correlation between the output of the coil when the temperature around the coil has a predetermined value, and the corrected displacement signal indicating the displacement of the position of the measured object that has been temperature-corrected obtained from the output of the coil, A displacement sensor, which 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 correction displacement signal corresponding to the actual temperature measured by the temperature measuring device from the correlation between the output of the coil and the correction displacement signal at at least one temperature,
The displacement sensor according to claim 1, wherein the displacement signal generation unit outputs the corrected displacement signal interpolated by the interpolation processing unit as the displacement signal.   The displacement sensor according to claim 2, wherein the interpolation processing unit interpolates the correlation so as to generate a new correlation so that the correction displacement signal changes linearly with respect to a change in the output of the coil. .   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 correction displacement signal at at least two temperatures different from each other. The displacement sensor according to item 3. A substrate on which the displacement signal generation unit is mounted,
A substrate temperature measuring device for measuring the temperature of the substrate,
5. The interpolation processing unit interpolates the correlation based on a temperature around the coil measured by the temperature measuring device and a temperature of the substrate measured by the substrate temperature measuring device. The displacement sensor according to any one of 1. A first correlation storage unit that stores a first correlation between the output of the coil and the corrected displacement signal at a first temperature;
A second correlation storage unit that stores a second correlation between the output of the coil and the correction displacement signal at a second temperature different from the first temperature,
The interpolation processing unit generates the second correlation by the interpolation processing of the first correlation while the displacement sensor is performing measurement using the first correlation, and generates the second correlation. Stored in the relation store,
The displacement signal generation unit generates the correction displacement signal based on the second correlation when the temperature measured by the temperature measuring device changes to the second temperature. Displacement sensor according to item. A first correlation storage unit that stores a first correlation between the output of the coil and the corrected displacement signal at a first temperature;
A second correlation storage unit that stores a second correlation between the output of the coil and the correction displacement signal at a second temperature different from the first temperature,
When the temperature measured by the temperature measuring device changes from the first temperature to the second temperature while the displacement sensor is measuring using the first correlation, The displacement sensor according to claim 2, wherein the second correlation is generated by an interpolation process of the first correlation and is stored in the second correlation storage unit. While generating an alternating current by performing an oscillating operation using the impedance of the coil, and having a self-excited oscillation circuit that outputs an oscillation signal,
8. The displacement sensor according to claim 1, wherein an oscillation level of the self-excited oscillation circuit changes under the influence of a change in impedance of the coil due to an eddy current generated in the object to be measured.

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