JPH0545108A - Measuring apparatus of displacement - Google Patents

Abstract

PURPOSE:To always obtain a correct measured value even at the time of movement of a movable element by enabling substantially simultaneous execution of measurement of a fine pitch and measurement of a rough pitch and a medium pitch at the time of absolute measurement. CONSTITUTION:A transmission waveform generating element 2 supplies a first transmission signal for a rough scale and a medium scale and a second transmission signal for a fine scale to an ABS (absolute) sensor 1 by time-division multiplexing. cut of detection signals subjected to the time-division multiplexing and outputted from the ABS sensor 1, signals based on the first transmission signal are extracted in a rough scale demodulation element 3 and a medium scale demodulation element 4, while signals out of the detection signals being based on the second transmission signal are extracted in a fine scale demodulation element 5. Since phase information for the rough scale and the medium scale and phase information for the fine scale are detected simultaneously substantially in phase detection elements 6 to 8, exact absolute displacement can be measured even when a slider of the ABS sensor 1 is shifted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement measuring device using a displacement sensor applied to a small measuring instrument such as a digital caliper, a digital micrometer and a height gauge.

[0002]

2. Description of the Related Art Small displacement measuring devices such as digital calipers, digital micrometers, and height gauges for displaying measured values on a liquid crystal display device or the like are generally of low power consumption type using a capacitance type displacement sensor or the like. It is popular. A capacitance type displacement sensor has a large number of electrodes arranged on a fixed element such as a main scale and a movable element such as a slider which moves relative to the fixed element, and the electrodes are moved as the movable element moves relative to the fixed element. The displacement amount is detected by extracting a signal of a periodic capacitance change generated between the patterns.

This type of displacement sensor is classified into two types, an incremental type and an absolute type, depending on the form of its output signal. The increment type measuring device detects the displacement amount by continuously counting the periodic signals generated by the movement of the slider from the reference position. For example, a movable element is formed with a large number of transmission electrodes and detection electrodes insulated from each other, and a fixed element has a large number of reception electrodes and transmission electrodes capacitively coupled to the transmission electrodes and the detection electrodes, respectively. They are formed in a state of being connected to each other. When the movable element is moved with respect to the fixed element while the multi-phase transmission signal is supplied to the transmission electrode, the capacitance between the transmission electrode and the reception electrode changes periodically, so that the detection detected by the detection electrode is performed. The phase of the signal also changes periodically. In the incremental type measuring device, the amount of relative displacement of the movable element with respect to the fixed element is obtained by counting the periodic change in the phase.

On the other hand, the absolute type displacement sensor is a sensor capable of obtaining the absolute position of the movable element with respect to the fixed element without performing continuous counting operation.
For example, in addition to outputting a periodic signal with a fine pitch that matches the arrangement pitch of the receiving electrodes, a periodic signal with a coarse pitch or an intermediate pitch is output by making the pitches of the receiving electrode and the transmission electrode slightly different. Then, it is possible to detect the absolute displacement amount of the movable element by combining the phase information of the periodic signals of these respective pitches.

[0005]

By the way, in the displacement measuring device using the absolute type displacement sensor,
In terms of measurement accuracy, if the phase pattern of the transmission signal given to the displacement sensor to obtain a periodic signal with a coarse pitch and an intermediate pitch is different from the phase pattern of the transmission signal given to the displacement sensor to obtain a periodic signal with a fine pitch. There is something to do. Here, assuming that the fine pitch measurement mode is the first measurement mode and the coarse pitch and intermediate pitch measurement modes are the second measurement modes, the absolute type displacement measurement has the first and second measurement modes. The measurement is performed sequentially to obtain the absolute displacement amount. However, in this case, since the timings of capturing the phase information in the first and second measurement modes are deviated, when the movable element is moving, the combination of the phase information is not successful and the correct measurement value is obtained. There is a problem that it can not be done.

Further, for example, in order to supplement the moving speed limit of the movable element in the incremental measurement, it has been proposed by the present inventor to shift from the incremental measurement to the absolute measurement when the movable element moves at a high speed. In this case, when the movable element decelerates and shifts from absolute measurement to incremental measurement, there is a problem that an error occurs in the measured value unless the correct absolute position is obtained as the reference value for incremental counting. .. Further, in the incremental measurement, it is necessary to continuously perform the counting operation, but if a special measurement mode such as scale contamination detection is executed, the incremental measurement operation is temporarily interrupted, so during this period, If the movable element moves, there is a problem that a correct count value cannot be obtained.

The present invention has been made in order to solve such a problem, and an object thereof is to provide a displacement measuring device which can always obtain an accurate measurement value even when a movable element is moving. And

[0008]

DISCLOSURE OF THE INVENTION A displacement measuring device according to the present invention includes a displacement sensor in which a capacitance value between the fixed element and the movable element changes according to a displacement amount of the movable element with respect to the fixed element, Transmission waveform generating means for supplying the displacement sensor with a first transmission signal for the first measurement mode and a second transmission signal for the second measurement mode; and with the supply of the first transmission signal, First output from displacement sensor
Based on the second detection signal output from the displacement sensor by the supply of the second transmission signal, the first signal processing means calculating the measurement value in the first measurement mode based on the detection signal In the displacement measuring device comprising a second signal processing means for calculating a measurement value in the second measurement mode, the transmission waveform generating means may detect the edges of the first transmission signal and the second transmission signal. The first and second transmission signals are multiplexed and supplied to the displacement sensor by combining while maintaining the height and the direction, and the first signal processing means outputs the first detection signal to the displacement sensor. The first signal is sampled and extracted at a sampling timing that captures an edge of the first transmission signal, and the second signal processing means is configured to extract the second signal.
Is detected and sampled at a sampling timing for capturing the edge of the second transmission signal.

[0009]

According to the present invention, the two types of transmission signals are combined while maintaining the heights and directions of the edges, multiplexed, and then supplied to the displacement sensor, and the detection signal output from the displacement sensor is first detected.
Since the signal is extracted and processed by the second signal processing circuit, the measurement in the first measurement mode and the measurement in the second measurement mode can be executed almost at the same time. Therefore, for example, during absolute measurement, fine pitch measurement and coarse pitch and intermediate pitch measurement can be performed almost simultaneously, and correct measurement values can always be obtained even when the movable element is moving. .. Also, for example, even during incremental measurement, other measurement modes such as contamination detection can be simultaneously executed without interrupting the counting operation.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of a displacement measuring device according to an embodiment of the present invention. This displacement measuring device is applied to small side length devices such as digital calipers, digital micrometer, digital height gauge and the like.

That is, the ABS sensor 1 is a capacitance type absolute type displacement sensor. The ABS sensor 1 is configured, for example, as shown in FIG. The slider 21, which is a movable element, is arranged to face the main scale 22, which is a fixed element, with a slight gap therebetween, and is movable in the measurement axis X direction. Slider 21
, The transmission electrodes 23 are arranged at a predetermined pitch Pt0. The transmission electrode 23 has a pitch Pr on the main scale 22.
First receiving electrode 24a and second receiving electrode 24 arranged in
It is capacitively coupled with b. The receiving electrodes 24a and 24b are
The first pitches Pt1 and Pt2 adjacent to each other along the arrangement direction
The transmission electrodes 25a and the second transmission electrodes 25b are connected in a one-to-one relationship. The transmission electrodes 25a and 25b are capacitively coupled to the first detection electrodes 26a and 26b and the second detection electrodes 27a and 27b provided on the slider 21 side, respectively.

The transmission electrodes 23 are commonly connected to every other seven electrodes to form eight electrode groups. These electrode groups include
Eight-phase periodic signals ah each having a phase difference of 45 °
Is supplied as the drive signal Sd. More specifically, these drive signals Sd are signals chopped by high frequency pulses as shown in FIG. The sin component of a large period is expressed by the following formula 1.

[0013]

## EQU1 ## Vn = Asin2.pi. {(T / T)-(n / 8)}

Here, A is the amplitude of the transmission signal Sd, T is the period of the transmission signal Sd, and n is the phase number (a, b, ..., H). The transmission signal Sd is generated and output from the transmission waveform generator 2 of FIG. The drive signal S is sent to the transmitting electrode 23
The pitch Wt of the electric field pattern generated by supplying d is 8 times the pitch Pt0 of the transmitting electrode 23, and this pitch Wt is set to N times the pitch Pr of the receiving electrodes 24a and 24b. Here, N is preferably an odd number such as 1, 3, 5, etc., and is set to 3 in this example. Therefore, the three or four receiving electrodes 24a and 24b are always capacitively coupled to the eight continuous transmitting electrodes 23. The reception electrodes 24a and 24b are formed by arranging triangular (or sinusoidal) electrode pieces so as to sandwich each other. The phase of the signal received by each of the receiving electrodes 24a and 24b is determined by the transmitting electrode 23 and the receiving electrode 24.
It is determined by the capacitive coupling area with a and 24b, but this changes depending on the relative position between the slider 21 and the main scale 22.

Receiving electrodes 24a, 24b and transmitting electrode 25
If a and 25b are formed at the same pitch, the detection electrodes 26a, 26b, 27a and 27b are simply the slider 2
Although the periodic signal repeated every time the position of 1 in the x direction changes by the pitch Pr is detected, the ABS sensor 1 detects displacements at three levels of a coarse pitch, an intermediate pitch and a fine pitch. Therefore, the transmission electrode 25
Actually, a and 25b are deviated from the receiving electrodes 24a and 24b by D1 and D2, respectively. Deviation amount D1, D2
Are each a function of the distance x in the measurement direction from the reference position x0, and can be expressed by the following equation 2.

[0016]

## EQU2 ## D1 (x) = (Pr-Pt1) x / Pr D2 (x) = (Pr-Pt2) x / Pr

Further, the detection electrodes 26a, 26b, 27a,
The pitches Wr1 and Wr2 of the waveform pattern of 27b are 3P each.
It is set to t1 and 3Pt2. FIG. 4A shows the transmitter electrode 2.
3 is a graph showing a change in capacitance between the detection electrode 26a and one of the three electrodes, and FIG. 4B shows a change in the capacitance according to the position x between one of the transmission electrodes 23 and the detection electrode 26b. It is a graph which shows. As shown in FIG. 4, the capacitance of the detection electrode 24 is set to a large period λ1 based on the deviation amount D1 (x).
The period Pr having a small pitch of a changes in a superimposed manner. This capacity is shown in Equation 3 below.

[0018]

## EQU3 ## Cn (B1) = Bsin2π {(x / λ1)-(n / 8)} + Csin2π {(x / Pr)-(3n / 8)} + D Cn (B2) =-Bsin2π {(x / λ1 )-(N / 8)} + Csin2π {(x / Pr)-(3n / 8)} + D

Here, B is the amplitude of a large cycle, C is the amplitude of a small cycle, and D is the offset value. Therefore, the reception signal B1 detected by the detection electrodes 26a and 26b
, B2 are respectively expressed by the following formula 4.

[0020]

[Equation 4]

Here, the electrode patterns are arranged so that the large period of the detection signals B1 and B2 is several tens of times the small period and the large period of the detection signals C1 and C2 is several tens of times the large period of the detection signals B1 and B2. When set, the displacement of each level can be obtained by the following mathematical expression 5.

[0022]

[Equation 5] C1-C2 (coarse scale) B1-B2 (medium scale) (B1 + B2)-(C1 + C2) (fine scale)

These calculations are performed by the coarse scale demodulation unit 3, the medium scale demodulation unit 4 and the fine scale demodulation unit 5 of FIG. The demodulation is performed, for example, by sampling the transmission waveform shown in FIG. 3 at a chop frequency, mixing the signals, and then performing low-pass filtering and binarization processing. As a result, each of the scale demodulators 3, 4, and 5 has a rectangular-wave phase signal CM in which phase information is carried by an edge.
P is output. Further, the detection signals B1, B2, C1, C2 output from the ABS sensor 1 are
5 is also being supplied. The contamination inspection demodulation unit 15 adds all detection signals B1, B2, C1, C2, which will be described later, detected by the ABS sensor 1 when the transmission signal for test is supplied from the transmission waveform generation unit 2 to the ABS sensor 1. Phase signal CMPCONT. Is output. This phase signal CMPCONT. Is input to the contamination detection unit 16. The contamination detection unit 16 outputs the phase signal CMPCONT. Based on AB
The contamination state of the S sensor 1 is detected.

The phase signals CMPCOA. , CMPMED. , CMPF
INE is input to the coarse phase detector 6, the medium phase detector 7, and the fine phase detector 8, respectively. These phase detectors 6 to
8, the count value of the internal counter (not shown) is latched at the rising or falling timing of each phase signal CMP, so that each phase signal CMP and the reference phase signal CP
A value corresponding to the phase difference with O is detected.

The phase values output from the phase detectors 6 to 8 are input to the absolute counter 10. The absolute counter 10 combines the phase values output from the phase detectors 6 to 8 to calculate the absolute displacement amount of the slider 21 with respect to the main scale 22. The phase value output from the fine phase detection unit 8 is input to the incremental counting unit 11. Incremental counting unit 1
1 calculates the displacement of the slider 21 with respect to the main scale 22 by up-counting and down-counting the periodic change of the phase value output from the fine phase detection unit 8.

On the other hand, the phase signals CMPMED. ，
The CMPFINE is also input to the speed detector 9.
The speed detector 9 detects the phase signal CMPFINE when the slider 21 is moving at a low speed or is stopped.
The signal detects the moving speed of the slider 21,
Is moving at high speed, the phase signal CMPME
D. The moving speed of the slider 21 is detected by. The speed detector 9 outputs the detected slider speed information to the circuit switching controller 12.

The circuit switching controller 12 includes a slider 21.
Is moving slowly or is stopping, the scale demodulating units 3 and 4, the phase detecting units 6 and 7, and the absolute counting unit 10 are stopped, and the fine scale demodulating unit 5 and the fine phase detecting unit 8 are Also, the incremental counting unit 11 is put into an operating state and switched to the incremental counting operation. Further, the circuit switching control unit 12 controls the scale demodulation unit 3 when the slider is moving fast.
4, the phase detectors 6 and 7 and the absolute counter 10 are activated, and the incremental counter 1
Stop 1 and switch to absolute counting operation.

Further, since the change of the electrostatic capacitance is as shown in the above equation 3, as shown in FIG. 5, it is different from the phase of the transmission signal Sd at the counting operation by the coarse scale and the medium scale, and the circuit switching control section. 12 is designed to be switched. Further, the circuit switching controller 12 switches the transmission waveform generator 2 so as to output the transmission waveform for contamination inspection based on the contamination inspection mode signal instructed from the outside.

The count value of the absolute counting unit 10 and the count value of the incremental counting unit 11 are combined by the count combining unit 13. Count synthesis unit 13
Is displayed on the display unit 14 such as an LCD in a form that is appropriately converted into an actual displacement amount.

Next, the operation of the displacement measuring apparatus according to this embodiment having the above-mentioned structure will be described. FIG. 6 is a diagram showing the relationship between the slider speed v and the counting / speed detection mode.

When the slider 21 starts to move from the stopped state, the circuit switching controller 12 causes the scale demodulator 3,
4, the phase detecting units 6 and 7 and the absolute counting unit 10 are stopped, the fine scale demodulating unit 5, the fine phase detecting unit 8 and the incremental counting unit 11 are in the operating state, and the transmission waveform generating unit 2 performs the fine scale counting operation. To generate a transmission waveform Sd. As a result, the incremental counting operation is started, and the count value held in the absolute counting section 10 is sequentially added or subtracted. At this time, the speed detecting unit 9 detects the moving speed of the slider 21 from the cycle of the phase signal CMPFINE output from the fine scale demodulating unit 5.

When the moving speed v of the slider 21 reaches about 80% of the theoretical limit speed v3 of the fine scale incremental counting, the circuit switching controller 12 causes the scale demodulators 3 and 4, the phase detectors 6 and 7, and the absolute controller. Counting unit 1
0 is the operating state, the fine scale demodulating unit 5, the fine phase detecting unit 8 and the incremental counting unit 11 are in the stopped state, and the transmission waveform generating unit 2 generates the transmission waveform Sd for the coarse scale and fine scale counting operations. .. As a result, the device shifts to the absolute counting mode. At this time, the lower digit of the display value is updated with a coarse interval, but when the slider is moving fast, the lower digit of the display value is not so noticeable, so there is no particular problem.
In this mode, the speed detector 9 operates in the medium scale demodulator 4
From the phase signal CMPMED. The moving speed of the slider 21 is detected from the cycle.

The moving speed v of the slider 21 is 1 of the speed v3.
When the speed is reduced to 5%, the operation again shifts to the incremental counting operation, but at this time, it is necessary to transfer the absolute displacement information to the counting / combining unit 13. For this reason, the circuit switching control unit 12 operates all the scale demodulation units 3, 4, 5 and the phase detection units 6, 7, 8 only for the period required for this delivery, and calculates the absolute count value including the fine scale. .. In this case, since the transmission signal Sd during the coarse scale and medium scale counting operation (first measurement mode) and the transmission signal Sd during the fine scale counting operation (second measurement mode) are different, during this period, The transmission signal Sd is temporarily multiplexed.

FIG. 7 shows 4 for coarse scale and medium scale.
It is a figure which shows the multiplexed signal M of the transmission signal b1 of 5 degree phase, and the transmission signal b2 of 135 degree phase for fine scales. In this way, the multiplexed signal M can be generated by synthesizing while maintaining the heights and directions of the edges of the transmission signals b1 and b2. When the multiplex signal M is supplied to the ABS sensor 1, the detection signals B1 detected by the scale demodulation units 3 to 5 are detected.
, B2, C1, C2 are also the multiplexed signal M'as shown in FIG. 8, for example. Therefore, in the coarse scale demodulator 3 and the medium scale demodulator 4, for example, as shown in FIG.
Of the multiplexed signal M ', which is the output of
Sampling to 3,34. As a result, S11,
A sinusoidal signal indicated by S12 is obtained. These signals S
11, S12 are added by the mixing circuit 35, low-pass filtered by the low-pass filter 36, and then the waveform shaping circuit 37.
And the rectangular phase signal CMPCOA. , CM
PMED. Becomes

On the other hand, in the fine scale demodulation section 5, as shown in FIG. 10, sampling clocks S2 and S2 are used.
′ Is obtained and the adder 4 is driven by these clocks S2 and S2
2, 43 and the multiplexed signal M ′ output from the subtractor 44 are sampled by the sample hold circuits 45, 46. As a result, sinusoidal signals indicated by S21 and S22 in the figure are obtained. These signals S21 and S22 are output to the mixing circuit 47.
Is added, and low-pass filtered by the low-pass filter 48, and then shaped by the waveform shaping circuit 49 to form a rectangular wave phase signal CMPFINE. When the absolute count value is obtained during this delivery period, the process thereafter shifts to the incremental count using the fine scale alone.

As described above, in this displacement measuring device, the transmission waveforms are temporarily multiplexed at the time of transfer to the incremental counting operation. Therefore, even if the slider 21 is moved, the coarse scale and the medium scale are moved. The phase information and the fine scale phase information can be obtained almost simultaneously. Therefore, a correct measurement value can always be obtained.

In the above embodiments, the present invention has been described with the coarse scale and medium scale measurement as the first measurement mode and the fine scale measurement as the second measurement mode, but the present invention is not limited to this. Not something. For example, in the case of an incremental measurement using a fine scale, it is necessary that the counting operation is continuous. However, when the ABS sensor 1 is checked during the incremental measurement, the inspection can be performed without impairing the continuity of the counting operation. It is desirable to be able to perform the operation. Therefore, assuming that the incremental measurement by the fine scale is the first measurement mode and the contamination detection operation of the ABS sensor 1 is the second measurement mode, the transmission signal Sd for the fine scale counting and the transmission signal Sd for the contamination detection are Should be multiplexed.

When contamination is detected, as a first step, first, a sine wave having a specific phase φ1 is supplied to the transmission signals a to d in FIG. 2 to detect detection signals B1, B2, C1 and C.
The contamination detection unit 16 detects the phase φ1 ′ of the signal obtained by adding all 2's. Next, as a second step, a sine wave of phase φ1 is supplied to the transmission signals e to f in FIG. 2 and the phase φ1 of the signal obtained by adding all the detection signals B1, B2, C1 and C2.
″ Is detected by the contamination detection unit 16. Finally, the detected phases φ1 ′ and φ1 ″ are compared, and if they are substantially the same, it is determined that there is no contamination, and if they are extremely different, contamination is determined. In this process, the transmission signal Sd for increment counting and the transmission signal Sd for contamination detection are multiplexed so that contaminants between the slider 21 and the main scale 22 are not interfered with by the increment counting operation. It is possible to detect the capacitance change due to.

[0039]

As described above, according to the present invention, 2
The signals are sent to the displacement sensor after being multiplexed by synthesizing while maintaining the height and direction of the edges of the types of transmission signals, and the detection signals output from the displacement sensor are extracted by the first and second signal processing circuits, respectively. Therefore, the measurement in the first measurement mode and the measurement in the second measurement mode can be executed almost at the same time. Therefore,
For example, during absolute measurement, fine pitch measurement and coarse pitch and intermediate pitch measurement can be performed almost simultaneously, and correct measurement values can always be obtained even when the movable element is moving. Also, for example, even during incremental measurement, other measurement modes such as contamination detection can be simultaneously executed without interrupting the counting operation.

[Brief description of drawings]

FIG. 1 is a block diagram of a displacement measuring device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of an ABS sensor in the displacement measuring device.

FIG. 3 is a waveform diagram showing an example of a transmission signal supplied to the sensor.

FIG. 4 is a graph showing a change in capacitance with respect to position in the sensor.

FIG. 5 is a schematic diagram showing a phase relationship of transmission signals supplied to the sensor.

FIG. 6 is a graph showing a relationship between a moving speed of a slider of the sensor and a counting mode and a speed detection mode.

FIG. 7 is a waveform diagram showing an example of a multiplexed transmission signal supplied to the sensor.

FIG. 8 is a waveform diagram for explaining a demodulation operation in each scale demodulation unit.

FIG. 9 is a block diagram showing configurations of a coarse scale demodulation unit and a medium scale demodulation unit.

FIG. 10 is a block diagram showing a configuration of a fine scale demodulation unit.

FIG. 11 is a waveform diagram showing a transmission waveform according to another embodiment of the present invention.

[Explanation of symbols]

1 ... ABS sensor, 2 ... Transmission waveform generator, 3 ... Coarse scale demodulator, 4 ... Medium scale demodulator, 5 ... Fine scale demodulator, 6 ... Coarse phase detector, 7 ... Medium phase detector, 8 ... Fine Phase detection unit, 9 ... Speed detection unit, 10 ... Absolute counting unit, 11 ... Incremental counting unit, 12 ... Circuit switching control unit, 13 ... Count synthesis unit, 14 ... Display unit, 15 ... Contamination inspection demodulation unit, 16 ... Contamination Detector, 21 ... Slider, 2
2 ... Main scale, 23 ... Transmission electrode, 24a ... 1st reception electrode, 24b ... 2nd reception electrode, 25a ... 1st transmission electrode, 25b ... 2nd transmission electrode, 26a, 26b ... 1st detection electrode, 27a, 27b ... Second detection electrode.

Claims (3)

[Claims] 1. A displacement sensor in which a capacitance value between the fixed element and the movable element changes according to a displacement amount of the movable element with respect to the fixed element, and a first displacement sensor for the first measurement mode. Based on the first detection signal outputted from the displacement sensor by the supply of the first transmission signal, and the transmission waveform generating means for supplying the second transmission signal for the second measurement mode and the second transmission signal for the second measurement mode. The second measurement based on a first signal processing means for calculating a measurement value in the first measurement mode and a second detection signal output from the displacement sensor in response to the supply of the second transmission signal. In a displacement measuring device comprising a second signal processing means for calculating a measured value of a mode, the transmission waveform generating means maintains the height and direction of edges of the first transmission signal and the second transmission signal. By synthesizing The first and second transmission signals are multiplexed and supplied to the displacement sensor, and the first signal processing means captures the first detection signal at an edge of the first transmission signal. Sampling and extracting at sampling timing, the second signal processing means,
A displacement measuring apparatus, wherein the second detection signal is sampled and extracted at a sampling timing that captures an edge of the second transmission signal. 2. The displacement sensor receives the first transmission signal in the first measurement mode and outputs a first detection signal having a coarse pitch according to a displacement amount of the movable element with respect to the fixed element. In the second measurement mode, an absolute displacement detection type sensor that receives the second transmission signal and outputs a second detection signal with a fine pitch according to the amount of displacement of the movable element with respect to the fixed element, The first and second signal processing circuits respectively extract phase information of the first and second detection signals, and calculate an absolute displacement amount of the fixed element with respect to the movable element based on a combined value thereof. The displacement measuring device according to claim 1, which is a thing. 3. The displacement sensor receives the first transmission signal in the first measurement mode and outputs a first detection signal according to a displacement amount of the movable element with respect to the fixed element, In the second measurement mode, the second detection signal is received and a second detection signal corresponding to a capacitance change due to contamination between the fixed element and the movable element is output.
The first signal processing circuit is for calculating a displacement amount of the fixed element with respect to the movable element based on the phase of the first detection signal, and the second signal processing circuit is for the second signal processing circuit. The displacement measuring device according to claim 1, wherein contamination of the displacement sensor is detected based on a phase of a detection signal.