JP2017142270A - Electrostatic capacity detector and sensor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic capacity detector that can remove noise added to a sensor output signal of a sensor while suppressing reduction in responsiveness to change in the electrostatic capacity of the sensor.SOLUTION: An electrostatic capacity detector 3 includes: a current supply unit 20 for applying a carrier voltage with a predetermined period to a sensor sheet 2 as an electrostatic capacity sensor; a converter 25 for converting a sensor output signal, which is a current signal output from the sensor sheet 2 according to the application of the carrier voltage, into a voltage signal; a rectification unit 27 for rectifying the sensor signal; a second low-pass filter unit 28 for removing a frequency component of the carrier voltage in the sensor output signal rectified by the rectification unit 27; and a filter unit 26 connected between the converter 25 and the rectification unit 27 for passing the sensor output signal, the cut-off frequency fof the filter unit 26 being set to be higher than the frequency of a commercial power source and the cut-off frequency fof the second low-pass filter unit 28 being set to be higher than the frequency of a commercial power source.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a capacitance detection device and a sensor system.

Conventionally, a capacitance type sensor device includes a capacitance type sensor composed of a capacitance element whose capacitance changes in response to an external input, and detects the capacitance of the capacitance type sensor. Some have a capacitance detecting device for outputting.
For example, the electrostatic capacitance detection device described in Patent Literature 1 applies a voltage application element for applying a rectangular wave having a predetermined period to an electrode on one end side of an electrostatic capacitance sensor and an electrode on one end side. A rectifier that rectifies the output signal output from the electrode on the other end of the sensor; and a smoothing capacitor that smoothes the output signal rectified by the rectifier. The capacitance detection device detects an output signal output from the electrode on the other end of the sensor when the rectangular wave is applied to the electrode on the one end side of the sensor, and detects the amplitude of the detected output signal. Based on this, the capacitance of the sensor is obtained (see, for example, Patent Document 1).

Japanese Patent No. 5326042

In addition to the signal component based on the capacitance of the sensor, the output signal of the capacitive sensor configured by the capacitive element as described above is caused by, for example, environmental noise such as electromagnetic waves emitted from surrounding electrical products. Noise components may be added.
Such environmental noise is often a relatively low frequency such as the frequency of a commercial power supply, and if such a noise component is added to the output signal, it is a factor that reduces the measurement accuracy of the capacitance of the sensor. Therefore, it is necessary to remove it.
In particular, when the movement of a living body such as a human body is detected by the sensor, the frequency of a signal detected in accordance with the movement appears as a very low frequency. It is necessary to remove as much as possible to secure.

In order to remove the noise component from the output signal of the sensor, it is conceivable to provide a low-pass filter for removing the noise after the rectifier.
By providing a low-pass filter, a noise component caused by a commercial power supply or the like is removed, and static measurement accuracy can be maintained.

  However, when a low-pass filter capable of removing relatively low frequency noise such as noise caused by commercial power is provided, noise components can be removed from the output signal, but only relatively low frequency components remain as signal components. For this reason, the change of the output signal after passing through the low-pass filter becomes excessively gentle, and the responsiveness of the output signal to the change of the capacitance of the sensor may be lowered.

  When the responsiveness of the output signal to the change in the sensor capacitance decreases, for example, when the change in the sensor capacitance is dynamically measured, the output signal follows the change in the sensor capacitance. This is not possible, and there is a problem that the accuracy of the measurement result of the capacitance is lowered.

  In other words, the cutoff frequency of the low-pass filter provided after the rectifier to remove noise must be set lower than the frequency of the noise to be removed. Although accurate measurement accuracy can be maintained, dynamic measurement accuracy may be reduced.

  The present invention has been made in view of such circumstances, and capacitance detection capable of removing noise added to the output signal of the sensor while suppressing a decrease in responsiveness to changes in the capacitance of the sensor. An object is to provide an apparatus and a sensor system.

  The present invention is a capacitance detection device that detects a capacitance of a capacitance type sensor whose capacitance changes in response to an external input, and the carrier voltage of a predetermined cycle is applied to the capacitance type sensor. A voltage supply unit that applies voltage, a conversion unit that converts a sensor output signal, which is a current signal output from the capacitive sensor in response to application of the carrier voltage, into a voltage signal, and the voltage signal that has been converted into the voltage signal A rectifier that rectifies the sensor output signal, a low-pass filter that removes a frequency component of the carrier voltage included in the sensor output signal rectified by the rectifier, and a connection between the converter and the rectifier A filter unit that allows the sensor output signal to pass therethrough, wherein the filter unit has a lower limit of a frequency band that allows a signal component to pass therethrough, and environmental noise around the capacitive sensor. Is set higher than the frequency, the cutoff frequency of the low pass filter portion is set higher than the frequency of the environmental noise.

According to the capacitance detection device configured as described above, the lower limit of the frequency band that is connected between the conversion unit and the rectification unit and allows the signal component to pass is the environment around the capacitance type sensor. Since the filter unit set higher than the noise frequency is provided, for example, even if environmental noise is added to the sensor output signal, the filter unit can remove the noise.
Further, in the low-pass filter section after the rectifying section, it is not necessary to remove the environmental noise, and the cutoff frequency of the low-pass filter section can be set higher than the frequency of the environmental noise. As a result, in order to remove environmental noise, the cutoff frequency of the low-pass filter section after the rectifier needs to be set lower than the environmental noise frequency, so that the cutoff frequency of the low-pass filter section is set higher than in the conventional example. It is possible to suppress the decrease in the response of the sensor output signal to the change in the capacitance of the capacitance type sensor.
As described above, according to the present invention, it is possible to remove noise added to the sensor output signal of the capacitance type sensor while suppressing a decrease in responsiveness to the change in capacitance of the capacitance type sensor. it can.

In the capacitance type sensor, noise such as electromagnetic waves generated by an electric product or the like that is operated by a commercial power source may be environmental noise and affected by the sensor output signal.
For this reason, in the capacitance detection device, the frequency of the environmental noise may be a frequency determined based on the frequency of the commercial power source.
In this case, even if an electromagnetic wave or the like generated by an electrical product or the like around the sensor becomes environmental noise, and noise having a frequency near the frequency of the commercial power supply is added to the sensor output signal, the noise can be reduced by the filter unit.
Further, as in the above conventional example, when the noise of the frequency of the commercial power source is to be removed by the low-pass filter unit, the cutoff frequency of the low-pass filter unit needs to be set lower than the frequency of the commercial power source. Since the cutoff frequency of the low-pass filter unit is set to be higher than the frequency of the commercial power supply, it is possible to suppress a decrease in the response of the sensor output signal to the change in the capacitance of the capacitance type sensor.
As a result, it is possible to remove noise added to the sensor output signal of the capacitance type sensor while suppressing a decrease in responsiveness to the change in capacitance of the capacitance type sensor.

In the capacitance detection device, it is preferable that the low-pass filter unit is constituted by a secondary or higher-order low-pass filter.
Furthermore, it is preferable that the filter unit is constituted by a second-order or higher-order high-pass filter.

Since the sensor output signal is output in response to the application of the carrier voltage, it may include a noise component included in the carrier voltage.
For this reason, the voltage supply unit includes a rectangular wave generation unit that generates a rectangular wave having a predetermined period, and a filter unit that converts the rectangular wave into a signal wave approximated to a sine wave, and the signal wave is transmitted to the carrier The voltage may be applied to the capacitive sensor.
In this case, since the noise included in the carrier voltage can be reduced, the frequency component of the carrier voltage can be easily removed by the low-pass filter unit, and the noise added to the sensor output signal can be more effectively removed.

  The detection device is a detection device that detects a surface state of the sample, and an irradiation unit that irradiates blinking light blinking at a predetermined cycle on the surface of the sample, and the blinking light is reflected by the surface of the sample. A light detection unit that detects reflected light; and a processing unit that identifies a surface state of the sample based on a change in the reflected light detected by the light detection unit, wherein the light detection unit detects the reflected light. A light receiving unit that outputs a sensor output signal that is a current signal corresponding to the intensity of light when it is received, a conversion unit that converts the sensor output signal into a voltage signal, and a rectifier that converts the sensor output signal converted into a voltage signal Connected between the converter and the rectifier, a rectifier that performs the processing, a low-pass filter that removes the frequency component of the carrier voltage contained in the sensor output signal rectified by the rectifier and gives the processed voltage to the processor Before A filter unit that allows a sensor output signal to pass therethrough, wherein the filter unit is set such that a lower limit of a frequency band in which a signal component is allowed to pass is set higher than a frequency of environmental noise around the light detection unit, and the low-pass filter The cut-off frequency of the part is set higher than the frequency of the environmental noise.

  In addition, a sensor system according to the present invention includes a capacitance type sensor whose capacitance changes in response to an external input, and a capacitance detection device that detects the capacitance of the capacitance type sensor. The capacitance detection device includes a voltage supply unit that applies a carrier voltage of a predetermined period to the capacitance type sensor, and the capacitance type sensor according to the application of the carrier voltage. A conversion unit that converts a sensor output signal, which is a current signal output from a voltage signal, a rectification unit that rectifies the sensor output signal converted to a voltage signal, and a sensor output signal rectified by the rectification unit. A low-pass filter unit that removes a frequency component of the carrier voltage included, and a filter unit that is connected between the conversion unit and the rectification unit and allows the sensor output signal to pass therethrough, The filter unit is configured such that a lower limit of a frequency band that allows a signal component to pass is set higher than an environmental noise frequency around the capacitive sensor, and a cutoff frequency of the low-pass filter unit is a frequency of the environmental noise. Is set higher than.

  According to the sensor system configured as described above, it is possible to remove noise added to the sensor output signal of the capacitance type sensor while suppressing a decrease in responsiveness to the change in capacitance of the capacitance type sensor.

  ADVANTAGE OF THE INVENTION According to this invention, the noise added to the output signal of the said sensor can be removed, suppressing the fall of the responsiveness with respect to the electrostatic capacitance change of a sensor.

It is a figure showing the whole sensor system composition concerning a 1st embodiment. (A) is a perspective view which shows an example of a sensor sheet | seat, (b) is the sectional view on the AA line of Fig.2 (a). It is a block diagram which shows an example of a structure of an electrostatic capacitance detection apparatus. It is a figure which shows the structural example of a conversion part. (A) is a figure which shows an example of a carrier voltage, (b) shows an example of an output when the sensor output signal output from a sensor sheet | seat is converted by the conversion part by application of the carrier voltage of (a). FIG. (A) is a figure which shows an example of the sensor output signal output from a conversion part, (b) is a figure which showed only the noise component added to the sensor output signal shown in (a), (c), It is a figure which shows the output from the said filter part when the sensor output signal shown to Fig.6 (a) is given to the filter part. (A) is a figure which shows the output when the sensor output signal shown in FIG.6 (c) is given to the rectification | straightening part, (b) gave the sensor output signal shown in (a) to the 2nd low-pass filter part. It is a figure which shows the signal wave output from the said 2nd low-pass filter part sometimes. It is a block diagram of the sensor system concerning a 2nd embodiment. (A) is a figure which shows an aspect when LED and a light-receiving part are installed in the sample, (b) is a figure which shows an aspect when dust has adhered to the surface of the sample.

Hereinafter, preferred embodiments will be described with reference to the drawings.
[1 First Embodiment]
[1.1 Overall system configuration]
FIG. 1 is a diagram illustrating an overall configuration of a sensor system according to the first embodiment. In the figure, the sensor system 1 includes a sensor sheet 2 and a capacitance detection device 3.
The sensor sheet 2 includes an elastomer dielectric layer formed in a planar shape and a pair of electrode layers formed on the front and back surfaces of the dielectric layer so as to sandwich the dielectric layer, and is formed in a planar shape. A capacitive element is configured.
The sensor sheet 2 is formed to be deformable (extendable) along a direction (surface direction) parallel to the front and back surfaces of the sensor sheet 2. When the sensor sheet 2 is deformed in the surface direction, the area of the electrode layer is changed following the deformation in the surface direction of the dielectric layer. For this reason, the electrostatic capacitance of the sensor sheet 2 changes according to the deformation of the sensor sheet 2.
The sensor sheet 2 is attached to a movable part of an object to be measured, such as a joint part of a human body, for example, by utilizing the characteristic that the capacitance changes according to the deformation of the sensor sheet 2, and the movable part It is used to grasp the movable state.

The sensor sheet 2 is attached to the movable part of the measurement object so as to be deformed according to the movement of the movable part. When the movable part moves, the sensor sheet 2 itself deforms accordingly, and the capacitance changes according to the deformation.
Therefore, if the movable part is moved with the sensor sheet 2 attached, and the correlation between the state of the movable part and the capacitance of the sensor sheet 2 is grasped in advance, the capacitance of the sensor sheet 2 can be increased. Based on this, the movable state of the measurement object can be grasped.
As described above, the sensor sheet 2 is configured to output information indicating the movable state of the movable part of the measurement object as a capacitance. That is, the sensor sheet 2 constitutes a capacitance type sensor whose capacitance changes in response to an external input such as a measurement object.

The capacitance detection device 3 has a function of detecting the capacitance of the sensor sheet 2. The capacitance detection device 3 applies a carrier voltage having a predetermined period to one electrode layer of the sensor sheet 2 and outputs a sensor output signal output from the other electrode layer of the sensor sheet 2 in accordance with the carrier voltage. To detect.
The electrostatic capacitance detection device 3 outputs a detection result signal representing a change in the electrostatic capacitance of the detected sensor sheet 2 by performing various signal processing on the detected sensor output signal of the sensor sheet 2.
The capacitance detection device 3 gives the detection result signal to the information processing device 4 connected to the capacitance detection device 3.

  Based on the detection result signal given from the capacitance detection device 3, the information processing device 4 generates information indicating the movable state of the movable part of the measurement object, and directs the information to the operator of the information processing device 4. Output.

[1.2 Configuration of sensor sheet]
Fig.2 (a) is a perspective view which shows an example of the sensor sheet | seat 2, FIG.2 (b) is AA sectional view taken on the line of Fig.2 (a).
2A and 2B, the sensor sheet 2 includes a sheet-like dielectric layer 11 and a front-side electrode formed on the surface (front surface: upper side in FIG. 2) of the dielectric layer 11. Layer 12A, back side electrode layer 12B formed on the back surface of dielectric layer 11 (lower side in FIG. 2), front side wiring 13A having one end connected to front side electrode layer 12A, and one end connected to back side electrode layer 12B Laminated back side wiring 13B, front side connecting terminal 14A attached to the other end of front side wiring 13A, back side connecting terminal 14B attached to the other end of back side wiring 13B, and laminated on the front side and back side of dielectric layer 11, respectively. The front side protective layer 15A and the back side protective layer 15B thus formed, and the adhesive layer 18 laminated on the back side protective layer 15B are provided.

The dielectric layer 11 is an elastomer sheet, and the thickness thereof is set to, for example, 10 to 1000 μm. The dielectric layer 11 is interposed between the front electrode layer 12A and the back electrode layer 12B, and has a function as a dielectric in the capacitive element.
The dielectric layer 11 is formed using an elastomer composition containing an elastomer and other optional components, and can be reversibly deformed so that the areas of the front and back surfaces thereof are changed.
Examples of the elastomer include natural rubber, isoprene rubber, nitrile rubber (NBR), ethylene propylene rubber (EPDM), styrene / butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), silicone rubber, fluorine rubber, Acrylic rubber, hydrogenated nitrile rubber, urethane rubber, and the like are used. Among these, urethane rubber and silicone rubber are preferable, and urethane rubber is more preferable.

Both electrode layers 12A and 12B are made of a conductive composition containing a conductive material. Both electrode layers 12A and 12B may be composed of conductive compositions having the same composition, or may be composed of conductive compositions having different compositions.
The front-side electrode layer 12A and the back-side electrode layer 12B have the same plan view shape, and the front-side electrode layer 12A and the back-side electrode layer 12B face each other across the dielectric layer 11. In the sensor sheet 2, a portion where the front electrode layer 12A and the back electrode layer 12B face each other functions as a capacitive element.
Note that the front electrode layer 12A and the back electrode layer 12B do not necessarily have to face each other across the dielectric layer, and at least part of them may be opposed to each other.

As the conductive material, for example, carbon nanotube, graphene, carbon nanohorn, carbon fiber, conductive carbon black, graphite, metal nanowire, metal nanoparticle, conductive polymer, etc. may be used alone, or two kinds You may use together. As the conductive material, carbon nanotubes are preferable. This is because it is suitable for forming an electrode layer excellent in conductivity and stretchability.
The conductive composition may contain, for example, a binder component in addition to the conductive material such as carbon nanotubes.
The binder component functions as a binder material, and by including the binder component, the adhesion to the dielectric layer and the strength of the electrode layer itself can be improved.

  Both wirings 13A and 13B that connect both electrode layers 12A and 12B and both connection terminals 14A and 14B are also made of the same conductive composition as both electrode layers 12A and 12B.

The front-side connection terminal 14A connected to the front-side electrode layer 12A via the front-side wiring 13A is, for example, a plate-like member formed using a copper plate or the like, and is exposed to the outside to detect capacitance. A connection line extending from the device 3 is connected.
The back side connection terminal 14B connected to the back side electrode layer 12B via the back side wiring 13B is also a plate-like member formed using a copper plate or the like, and is exposed to the outside to detect capacitance. A connection line extending from the device 3 is connected.
The sensor sheet 2 receives the carrier voltage given from the capacitance detection device 3 by the front side connection terminal 14A, and outputs a sensor output signal corresponding to the carrier voltage from the back side connection terminal 14B.

Both the protective layers 15A and 15B are provided to electrically insulate the electrode layers 12A and 12B and the like and protect them from the external environment. Moreover, both the protective layers 15A and 15B also have a function as a reinforcing member that increases the strength and durability of the sensor sheet 2 as a whole.
The material of the protective layers 15A and 15B is not particularly limited, and can be appropriately selected according to the required characteristics. Specific examples of the material of the protective layers 15A and 15B include the same elastomer composition as the material of the dielectric layer 11.

  The adhesive layer 18 is a layer provided for attaching the sensor sheet 2 to the measurement object, and is capable of being deformed according to the operation of the movable part when attached to the surface of the movable part of the measurement object. Adhesive strength to such an extent that it can be adhered to.

Since the dielectric layer 11 is made of an elastomer, the sensor sheet 2 can be deformed (stretched) in the plane direction as described above. When the dielectric layer 11 is deformed in the plane direction, the front side electrode layer 12A and the back side electrode layer 12B, and the front side protective layer 15A and the back side protective layer 15B are deformed following the deformation.
As the sensor sheet 2 is deformed, the capacitance of the detection unit changes in correlation with the deformation amount of the dielectric layer 11. Therefore, the deformation state of the sensor sheet 2 can be grasped by detecting the change in capacitance.

[1.3 Configuration of Capacitance Detection Device 3]
FIG. 3 is a block diagram illustrating an example of the configuration of the capacitance detection device 3. As illustrated in FIG. 3, the capacitance detection device 3 includes a voltage supply unit 20 for applying a carrier voltage to the sensor sheet 2 at a predetermined period.
The voltage supply unit 20 includes a rectangular wave generation unit 21 and a first low pass filter (LPF: Low pass filter) unit 22.
The rectangular wave generator 21 has a function of generating a rectangular wave having a predetermined period. The rectangular wave generation unit 21 applies a bias voltage to the generated rectangular wave and converts it to a waveform that swings around 0V. The rectangular wave generation unit 21 gives the converted rectangular wave to the first low-pass filter unit 22.
The first low-pass filter unit 22 has a function of converting a given rectangular wave into a signal wave approximated to a sine wave by passing a signal in a frequency band lower than a predetermined cutoff frequency. That is, the rectangular wave generated by the rectangular wave generation unit 21 is converted into a signal wave that approximates a sine wave by passing through the first low-pass filter unit 22.

  When the capacitance detection device 3 of the present embodiment is configured to operate with a predetermined intermediate reference voltage by applying a predetermined bias voltage as the entire device, the voltage supply unit 20 has an amplitude center. A signal wave having a waveform that becomes an intermediate reference voltage is generated.

The voltage supply unit 20 applies a signal wave approximated to the sine wave converted by the first low-pass filter unit 22 to the sensor sheet 2 as a carrier voltage.
The first low-pass filter unit 22 is connected to the front side connection terminal 14 </ b> A (see FIG. 2) of the sensor sheet 2 via the connection line 23. Therefore, the carrier voltage is applied to the sensor sheet 2 through the connection line 23.

The carrier voltage amplitude voltage V ₀ and the frequency f ₀ , which are signal waves approximate to a sine wave, are set in advance according to the capacitance of the sensor sheet 2 and the like.
The waveform of the rectangular wave generated by the rectangular wave generation unit 21 and the characteristics of the first low-pass filter unit 22 are set so as to obtain a carrier voltage in which the amplitude voltage V ₀ and the frequency f ₀ are set to predetermined values. ing.

  In this way, the voltage supply unit 20 generates a carrier voltage having a predetermined period, and applies the generated carrier voltage to the sensor sheet 2.

The back side connection terminal 14 </ b> B (see FIG. 2) of the sensor sheet 2 is connected to the conversion unit 25 of the capacitance detection device 3 via the connection line 24.
The sensor sheet 2 gives a sensor output signal to the conversion unit 25 in response to the application of the carrier voltage from the voltage supply unit 20.
The conversion unit 25 has a function of converting a sensor output signal, which is a current signal output from the sensor sheet 2 in response to the application of the carrier voltage, into a voltage signal.

  FIG. 4 is a diagram illustrating a configuration example of the conversion unit 25. As shown in FIG. 4, the conversion unit 25 includes an operational amplifier 25a and a resistance element 25b. 4 shows the sensor sheet 2 and the voltage supply unit 20 in addition to the conversion unit 25.

The sensor sheet 2 is connected to the inverting input terminal of the operational amplifier 25a. The non-inverting input terminal of the operational amplifier 25a is grounded.
The resistance element 25b is connected between the output terminal and the inverting input terminal of the operational amplifier 25a, and has a function as a feedback resistor.
The operational amplifier 25a adjusts the current flowing through the resistance element 25b and the current flowing through the sensor sheet 2 to be equal.

Here, when the carrier voltage is represented by the following formula (1), the current I flowing through the sensor sheet 2 is represented by the following formula (2).
Carrier voltage V _C = V ₀ sin (2πf ₀ t) (1)
Current I = j2πf ₀ CV ₀ sin (2πf ₀ t) (2)

In the above formula (1), V ₀ represents the amplitude voltage of the carrier voltage, f ₀ represents the frequency of the carrier voltage, and t represents time. In the above formula (2), j represents an imaginary number, and C represents the capacitance of the sensor sheet 2.
As described above, since the operational amplifier 25a is adjusted so that the current flowing through the resistance element 25b and the current flowing through the sensor sheet 2 are equal, the output voltage _Vout of the operational amplifier 25a is expressed by the following equation (3). The
Output voltage V _out = j2πf ₀ CRV ₀ sin (2πf ₀ t)
... (3)

In the above formula (3), R represents the resistance value of the resistance element 25b.
As shown in the above equation (3), the amplitude of the output voltage V _out of the operational amplifier 25 a is proportional to the capacitance C of the sensor sheet 2. Therefore, the change in the capacitance C of the sensor sheet 2 can be obtained from the amplitude of the output voltage _Vout of the operational amplifier 25a. Also, the capacitance C of the sensor sheet 2 can be obtained from the ratio between the amplitude voltage V ₀ of the carrier voltage and the output voltage V _out of the operational amplifier 25a.

As described above, the conversion unit 25 converts the current I as the sensor output signal output from the sensor sheet 2 into the output voltage _Vout as the voltage signal. As shown in the above formulas (2) and (3), the current I and the output voltage _Vout as the sensor output signal have information indicating the capacitance C of the sensor sheet 2 as an amplitude.

FIG. 5A is a diagram illustrating an example of the carrier voltage. In FIG. 5A, the vertical axis represents voltage, and the horizontal axis represents time (t).
As shown in FIG. 5A, the carrier voltage V _C is output as a signal wave whose amplitude voltage is constant at V ₀ . Note that the carrier voltage V _C is generated as a signal wave approximated to a sine wave as described above.
In the present embodiment, the frequency f ₀ of the carrier voltage is set to 5 kHz, for example.

FIG. 5B is a diagram illustrating an example of an output when the conversion unit 25 converts the sensor output signal output from the sensor sheet 2 by applying the carrier voltage in FIG.
FIG. 5B shows an example of a sensor output signal when the sensor sheet 2 is deformed and the capacitance of the sensor sheet 2 is changed over time.

As shown in FIG. 5 (b), the sensor output signal converted into the output voltage _Vout by the conversion unit 25 has the amplitude voltage fluctuating with time as the capacitance of the sensor sheet 2 changes with time. doing.
As described above, since the amplitude of the output voltage _Vout of the operational amplifier 25a is proportional to the capacitance C of the sensor sheet 2, a change in the capacitance C of the sensor sheet 2 appears in the amplitude of the output voltage _Vout . .
That is, the envelope E of the sensor output signal shown in FIG. 5B represents a change in the capacitance C of the sensor sheet 2.
Since the frequency of the carrier voltage is set to 5 kHz, the sensor output signal after being converted by the conversion unit 25 has the same frequency component of 5 kHz as the frequency f _{0 of the} carrier voltage and the electrostatic capacitance of the sensor sheet 2. A component indicating a change in the capacitance C is included. The frequency of the component indicating the change in the capacitance C included in the sensor output signal can be expressed as the following formula (4).
Frequency of component indicating change in capacitance C included in sensor output signal =
f ₀ ± f _e (4)
In Equation (4), _fe is a frequency of a component indicating a change in the capacitance C in a state where it is not modulated by the carrier voltage.

As described above, the conversion unit 25 converts the sensor output signal that is a current signal output from the sensor sheet 2 into the output voltage _Vout that is a voltage signal in response to the application of the carrier voltage.

Returning to FIG. 3, the conversion unit 25 gives the sensor output signal converted into the output voltage _Vout which is a voltage signal to the filter unit 26 connected to the subsequent stage of the conversion unit 25.

  The filter unit 26 is configured by a high pass filter. The filter unit 26 has a function of allowing the sensor output signal to pass by allowing passage of a signal component in a frequency band higher than a preset cutoff frequency. Further, the filter unit 26 has a function of limiting and removing the passage of noise components existing in a frequency band lower than the cut-off frequency. The filter unit 26 of the present embodiment is configured using a third-order high-pass filter using an operational amplifier.

FIG. 6A is a diagram illustrating an example of a sensor output signal output from the conversion unit 25.
In the sensor output signal shown in FIG. 6A, for example, the center of amplitude fluctuates gently along the time axis direction as compared with the sensor output signal shown in FIG. That is, low frequency noise having a frequency lower than the frequency of the sensor output signal is added to the sensor output signal shown in FIG.
Further, high-frequency noise is also added to the sensor output signal shown in FIG.
That is, a sensor output signal to which a noise component is added is given to the filter unit 26.

FIG. 6B is a diagram showing only the noise component added to the sensor output signal shown in FIG.
In FIG. 6B, the low frequency noise includes environmental noise caused by the environment around the sensor sheet 2 as a main component.
The environmental noise according to the present embodiment is, for example, noise generated due to the influence of electromagnetic waves generated by electrical products installed around the sensor sheet 2 or a direct current power source included in the own system. Environmental noise caused by surrounding electrical products, DC power supplies, and the like is added to the sensor output signal via the sensor sheet 2 and the like.
The noise generated by such an electric product or the like includes a frequency component of a commercial power source. Furthermore, noise generated by a converter or the like included in a DC power supply includes a noise component caused by ripples generated when rectifying AC obtained from a commercial power supply and a noise component due to switching. Such noise generated when AC is rectified includes a frequency component twice the frequency of the commercial power supply. Therefore, the frequency of environmental noise is 50 to 120 Hz.

In FIG. 6B, the high frequency noise appears in a spike shape, and is added to the sensor output signal as noise having a frequency higher than the frequency f _{0 of the} carrier voltage. Such high-frequency noise is generated due to each component included in the capacitance detection device 3 or mixed from the outside to be added to the sensor output signal.

Here, the cutoff frequency f _C1 of the filter unit 26 is set to be higher than 50 to 120 Hz, which is the frequency of environmental noise, and lower than the frequency f _{0 of the} carrier voltage. More specifically, when the frequency obtained by subtracting the frequency to be acquired as a component indicating the change in the capacitance C of the sensor sheet 2 from the frequency f _{0 of the} carrier voltage is f _g , the cutoff frequency f _C1 of the filter unit 26 is It is set to be lower than the frequency f _g. More specifically, the cutoff frequency f _C1 of the filter unit 26 is set to 3 kHz.
Therefore, the allowable sensor output signal which the noise is added is, given from converter 25 to the filter unit 26, the filter unit 26, a passage for the sensor output signals present in a frequency band around the frequency f ₀ of the carrier voltage Then, the passage of low-frequency noise including environmental noise having a frequency of 50 to 120 Hz as a main component is blocked.
Therefore, low frequency noise is removed from the sensor output signal after passing through the filter unit 26.

FIG. 6C is a diagram showing an output from the filter unit 26 when the sensor output signal shown in FIG.
In the sensor output signal shown in FIG. 6 (c), the amplitude voltage fluctuates with time in a state where the center of the amplitude is substantially constant at around 0V, and low frequency noise is removed.
On the other hand, high frequency noise that is higher than the cutoff frequency of the filter unit 26 is not removed and remains added to the sensor output signal.

  Returning to FIG. 3, when the sensor output signal to which noise is added is given from the conversion unit 25, the filter unit 26 outputs the sensor output signal after removing the low-frequency noise as described above. This is given to the rectifying unit 27 connected to the subsequent stage.

The rectification unit 27 is configured by a half-wave rectification circuit using an operational amplifier, and rectifies the sensor output signal supplied from the filter unit 26 by half-wave.
Further, a second low-pass filter unit 28 is connected to the subsequent stage of the rectifying unit 27.
The second low-pass filter unit 28 allows a signal in a frequency band lower than a preset cut-off frequency to pass, thereby passing a component indicating capacitance, which is a component included in the sensor output signal after half-wave rectification. Allow. The second low-pass filter unit 28 has a function of removing the frequency component of the carrier voltage and high-frequency noise. The second low-pass filter unit 28 of this embodiment is configured using a third-order low-pass filter using an operational amplifier.

FIG. 7A is a diagram showing an output when the sensor output signal shown in FIG. As shown in FIG. 7A, the rectification unit 27 performs half-wave rectification on the sensor output signal provided from the filter unit 26 and outputs the result.
The above-described high-frequency noise is added to the half-wave rectified sensor output signal shown in FIG.
Therefore, the rectification unit 27 provides the second low-pass filter unit 28 with a half-wave rectified sensor output signal to which high-frequency noise is added.

The cut-off frequency f _C2 of the second low-pass filter unit 28 is set lower than the frequency f ₀ of high-frequency noise or carrier voltage. That is, the cutoff frequency f _C2 of the second low-pass filter unit 28 is set to a value that can remove the frequency component of the carrier voltage and the high-frequency noise while leaving the component indicating the capacitance.
Therefore, when the sensor output signal subjected to half-wave rectification, to which high-frequency noise is added, is given to the second low-pass filter unit 28, the second low-pass filter unit 28 allows passage of a component indicating capacitance, The high-frequency noise or the frequency component of the carrier voltage that causes a ripple with respect to the component indicating the capacitance when remaining is blocked.
As a result, the high frequency noise and the frequency component of the carrier voltage are removed from the signal wave after passing through the second low pass filter unit 28.

Note that the low-frequency noise is removed from the sensor output signal subjected to half-wave rectification shown in FIG. Therefore, the second low-pass filter unit 28 does not need to consider limiting the passage of the low-frequency noise. For this reason, the cut-off frequency f _C2 of the second low-pass filter unit 28 of the present embodiment is set to be higher than 50 to 120 Hz that is a frequency of low-frequency noise (environmental noise).

For this reason, as in the above-described conventional example, in order to remove noise at the frequency of the commercial power source, which is a predetermined frequency, the cutoff frequency of the low-pass filter after the rectifier is set lower than the frequency of the commercial power source to limit the passage of the noise. Compared to the case, in the present embodiment, the cutoff frequency f _C2 of the second low-pass filter unit 28 can be set higher. As a result, it is possible to suppress a decrease in the response of the sensor output signal to the change in the capacitance C of the sensor sheet 2.

FIG. 7B is a diagram illustrating a signal wave output from the second low-pass filter unit 28 when the sensor output signal illustrated in FIG. 7A is supplied to the second low-pass filter unit 28.
In FIG. 7B, a diagram F shows a signal wave output from the second low-pass filter unit 28.
The diagram F represents the envelope of the sensor output signal of FIG. 7A by removing the high frequency noise and the frequency component of the carrier voltage from the sensor output signal shown in FIG.
As described above, the sensor output signal represents a change in the capacitance C of the sensor sheet 2 depending on its amplitude. Accordingly, a diagram F in FIG. 7B represents a change in the capacitance C of the sensor sheet 2.

  Returning to FIG. 3, the second low-pass filter unit 28 represents a change in the capacitance C of the sensor sheet 2 shown in FIG. 7B when the sensor output signal subjected to the half-wave rectification is supplied from the rectification unit 27. The signal wave is supplied as a detection result signal to the output unit 29 connected to the subsequent stage of the second low-pass filter unit 28.

  The output unit 29 performs signal processing such as amplification and gain adjustment on the detection result signal provided from the second low-pass filter unit 28, and provides the information processing apparatus 4 with the detection result signal subjected to signal processing.

The information processing device 4 is configured by, for example, a computer, and performs processing on a given detection result signal to obtain the value of the capacitance C of the sensor sheet 2 or the movable part of the measurement object. Information indicating the movable state is generated, and result information regarding the detection result is generated.
The information processing device 4 outputs the generated result information to the operator of the information processing device 4.

In the present embodiment, the second low-pass filter unit 28 gives the detection result signal to the output unit 29. However, the detection result signal is sent between the second low-pass filter unit 28 and the output unit 29. An amplifier for amplification and an incomplete differentiation circuit may be provided.
In this case, the amplifier can detect a minute change by amplifying the detection result signal. The incomplete differentiation circuit operates so as to adjust the voltage offset to the level of the amplified detection result signal.

[1.4 Effects]
The capacitance detection device 3 of the present embodiment outputs a voltage supply unit 20 that applies a carrier voltage of a predetermined period to the sensor sheet 2 that is a capacitance type sensor, and is output from the sensor sheet 2 in accordance with the application of the carrier voltage. Included in the sensor output signal rectified by the rectifier 27, the rectifier 27 that rectifies the sensor output signal converted into the voltage signal, and the rectifier 27 that rectifies the sensor output signal converted into the voltage signal. A second low-pass filter unit 28 for removing a frequency component of the carrier voltage; and a filter unit 26 connected between the conversion unit 25 and the rectification unit 27 and allowing the sensor output signal to pass therethrough. The cut-off frequency f _C1, which is the lower limit of the frequency band that allows signal components to pass, is higher than the frequency of the commercial power supply that is the frequency of environmental noise around the sensor sheet 2. The cutoff frequency f _C2 of the second low-pass filter unit 28 is set higher than the frequency of the commercial power supply.

According to the capacitance detection device 3 configured as described above, the filter unit 26 that is connected between the conversion unit 25 and the rectification unit 27 and whose cutoff frequency f _C1 is set higher than the frequency of the commercial power supply is provided. Thus, even when noise at the frequency of the commercial power supply is added to the sensor output signal, the filter unit 26 can remove the noise.
Further, in the second low-pass filter unit 28 subsequent to the rectifying unit 27, since the noise of the frequency of the commercial power source is removed by the filter unit 26, it is not necessary to remove the noise of the frequency of the commercial power source. Therefore, the cutoff frequency f _C2 of the second low-pass filter unit 28 can be set higher than the frequency of the commercial power supply. As a result, the cutoff frequency f _C2 of the second low-pass filter unit 28 can be set higher than that of the conventional example. Accordingly, it is possible to suppress a decrease in the response of the sensor output signal to the change in the capacitance C of the sensor sheet 2.
Further, the second low-pass filter unit 28 can remove high-frequency noise and frequency components of the carrier voltage.
As described above, according to the capacitance detection device 3 of the present embodiment, it is included in the sensor output signal of the sensor sheet 2 while suppressing a decrease in responsiveness to changes in the capacitance C of the sensor sheet 2. It is possible to remove environmental noise caused by the commercial power source. In addition, high frequency noise can be removed.

[2 Second Embodiment]
FIG. 8 is a block diagram of a sensor system according to the second embodiment. In the figure, the sensor system 40 of this embodiment includes an irradiation device 41 that irradiates light on the surface of a sample 50 and a light detection device 42. An information processing device is connected to the subsequent stage of the light detection device 42. The information processing apparatus receives the detection result signal output from the light detection device 42 and generates result information regarding the surface state, such as whether or not the surface 50a of the sample 50 has changed and whether or not dust has adhered.

The irradiation device 41 includes an LED (Light Emitting Diode) 45 that is a light source that irradiates the surface of the sample 50, and a lighting control unit 46 that controls the LED 45.
The LED 45 is provided so that light can be applied to the surface of the sample 50. The lighting control unit 46 controls the LED 45 so that the surface of the sample 50 is irradiated with blinking light that blinks at a predetermined cycle.

The light detection device 42 is a device that detects the reflected light reflected by the surface of the sample 50 by the light irradiated by the irradiation device 41, and includes a light receiving unit 47 that receives the reflected light, a conversion unit 25, a filter unit 26, A rectifying unit 27, a second low-pass filter unit 28, and an output unit 29 are provided.
The light receiving unit 47 is configured by a PD (Photo Diode), and outputs a sensor output signal that is a current signal corresponding to the received light intensity of the received reflected light. The light receiving unit 47 is connected to the subsequent conversion unit 25, and provides a sensor output signal to the conversion unit 25.

The conversion unit 25, the filter unit 26, the rectification unit 27, the second low-pass filter unit 28, and the output unit 29 have the same configuration as that of the first embodiment.
Therefore, each part converts the sensor output signal, which is a current signal corresponding to the received light intensity of the reflected light, into a voltage signal, detects a change in the received light intensity of the reflected light from the sensor output signal converted into the voltage signal, and receives the received light intensity. A signal wave representing the change in the signal is supplied as a detection result signal to the information processing apparatus connected to the subsequent stage of the output unit 29.

FIG. 9A is a diagram illustrating an aspect when the LED 45 and the light receiving unit 47 are installed on the sample 50. In FIG. 9A, the alternate long and short dash line indicates a light beam.
In FIG. 9A, the LED 45 is installed so that the irradiation angle of the flashing light is close to parallel with the surface 50 a of the sample 50. In addition, the light receiving unit 47 is disposed immediately above the irradiation range irradiated with the flashing light from the LED 45 on the surface 50 a of the sample 50.

Since the blinking light is irradiated at an angle close to parallel to the surface 50a, the reflected light reflected by the surface 50a is also reflected at an angle near parallel to the surface 50a.
For this reason, for example, as shown in FIG. 9A, if there is nothing on the surface 50a, the reflected light is not directly irradiated toward the light receiving unit 47.
Therefore, in this case, the received light intensity of the reflected light received by the light receiving unit 47 appears low.

FIG. 9B is a diagram illustrating an aspect when dust is attached to the surface 50 a of the sample 50.
In FIG. 9B, when the dust 55 is present on the surface 50a, the blinking light is applied to the dust, thus causing scattered light.
Unlike the reflected light, this scattered light is scattered around. For this reason, the light receiving unit 47 receives the scattered light with a light receiving intensity higher than the light receiving intensity of the reflected light.
That is, when there is no dust on the surface 50a, the light reception intensity detected by the light detection device 42 is relatively low, and when there is dust on the surface 50a, the light reception intensity detected by the light detection device 42 is relatively high. Become.
The sensor system 40 according to the present embodiment detects the surface state such as the presence / absence of a change in the surface 50a of the sample 50 and the presence / absence of dust adhesion based on the difference in the received light intensity.

Here, for example, as shown in FIG. 9B, when the detection of the surface state by the sensor system 40 is performed under an illumination environment with the fluorescent lamp 60, the light receiving unit 47 of the light detection device 42 is Direct light or reflected light is received.
Thereby, noise due to receiving light from the illumination may be added to the sensor output signal output from the light receiving unit 47 in addition to the information indicating the surface state of the surface 50a.
Such noise caused by light from illumination is environmental noise caused by the environment around the sensor.

  Some fluorescent lamps repeatedly blink at a commercial power supply frequency (50 to 60 Hz). In such a case, the frequency of environmental noise added to the sensor output signal output from the light receiving unit 47 is 50 to 60 Hz. Become.

In contrast, the present embodiment also includes the filter unit 26 that is connected between the conversion unit 25 and the rectification unit 27 and has a cutoff frequency f _C1 set higher than the frequency of the commercial power supply. Even if noise at the frequency of the commercial power supply is added as environmental noise to the output signal, the noise can be removed by the filter unit 26.

[Others]
The present invention is not limited to the above embodiment.
For example, in the sensor system of the first embodiment, a case where the sensor sheet 2 is attached to a movable part of a measurement object such as a joint part of a human body and the movable state of the movable part is measured is illustrated. In this case, the frequency of environmental noise is 50 to 120 Hz.

  On the other hand, the measurement target of the sensor system is not limited to a relatively gradual displacement such as an operation of a joint part of a human body. Depending on the measurement object, unnecessary noise may be given due to the measurement object itself, in addition to the displacement caused by the operation of the measurement object itself. In such a case, the environmental noise is not limited to the frequency determined based on the frequency of the commercial power source as shown in the first embodiment.

For example, when measuring the expansion / contraction deformation action of a gut when a tennis racket is hit by a sensor system, the gut itself may be deformed due to vibration or the like, in addition to the entire gut performing expansion / contraction deformation operation as a racket surface. is there. The vibration frequency of such a gut itself is about 5 kHz.
Such a displacement other than the expansion / contraction deformation operation of the entire gut has a low relationship with the expansion / contraction deformation operation of the entire gut and appears as noise in the sensor output signal.

Therefore, as described above, when the expansion / contraction deformation operation of the tennis racket gut is measured by the sensor system, the frequency of the environmental noise is set to less than 5 kHz, and the filter unit 26 and the second low-pass filter unit 28 are configured accordingly. Set the cutoff frequency.
Thereby, the environmental noise at the time of measuring the expansion-contraction deformation | transformation operation | movement of the gut of a tennis racket can be removed.

  In the first embodiment, the case where the frequency of the carrier voltage is set to 5 kHz is exemplified. However, the frequency of the carrier voltage only needs to be set higher than the frequency of the noise to be removed by the filter unit 26. For example, it can be set to 10 times or more the frequency of the noise to be removed by the filter unit 26.

  Moreover, in the said 1st Embodiment, although the case where the sensor sheet | seat 2 which is a capacitive element which is formed in planar shape and expands-contracts in a surface direction was used as an electrostatic capacitance type sensor, for example, a movable side electrode and And a capacitance-type sensor configured to change the capacitance between the two electrodes by moving the movable-side electrode by an external input such as acceleration. be able to.

In the first embodiment, a signal wave approximated to a sine wave is used as the carrier voltage. However, it may be approximated to a sine wave and used as a carrier voltage as a rectangular wave. However, when the rectangular wave is used as the carrier voltage, the output of the sensor sheet 2 becomes larger than necessary, and an excessive current may flow through the conversion unit 25. Therefore, the carrier voltage is preferably a sine wave or a signal wave approximated to a sine wave.
Since the sensor output signal is output in response to the application of the carrier voltage, it may include a noise component included in the carrier voltage.
For this reason, in the first embodiment, the voltage supply unit 20 is a rectangular wave generation unit 21 that generates a rectangular wave having a predetermined period, and a filter unit that converts the rectangular wave into a signal wave that approximates a sine wave. 1 low-pass filter section 22, and applies the signal wave as a carrier voltage to sensor sheet 2.
Thereby, since the noise contained in the carrier voltage can be reduced, the frequency component of the carrier voltage can be easily removed by the second low-pass filter unit 28. Therefore, noise contained in the sensor output signal can be more effectively removed.

  In each of the above embodiments, the case where a high-pass filter is used for the filter unit 26 has been described. However, a band-pass filter may be used instead of the high-pass filter. In this case, the cut-off frequency on the low frequency side, which is the lower limit of the frequency band that allows passage of the signal component, is set higher than the frequency of the environmental noise.

In each of the above embodiments, a case where a third-order high-pass filter is used for the filter unit 26 has been described. However, for example, a first-order or second-order high-pass filter other than the third-order may be used.
It should be noted that the second or higher order high-pass filter has a steeper characteristic as compared with the first-order high-pass filter, so that it is easier to set so that only signals in the necessary frequency band pass. Become.
Further, as in the case of the filter unit 26, the second low-pass filter unit 28 also uses a third-order low-pass filter in the above embodiment, but a primary or secondary low-pass filter other than the third-order filter may be used. Good. Since the low-pass filter of the second or higher order has a steeper characteristic as compared with the first-order high-pass filter, it is easier to set so that only a signal in a necessary frequency band is passed in this case as well. It becomes.

  In each of the above embodiments, the case where the rectifying unit 27 performs half-end rectification has been described, but the rectifying unit 27 may be configured to perform full-wave rectification. In this case, the value indicating the amplitude of the rectified sensor output signal output from the rectification unit 27 is twice that when half-end rectification is performed. For this reason, the component which shows the electrostatic capacitance contained in a sensor output signal increases, and the removal of the frequency component of a carrier voltage becomes easy in the 2nd low-pass filter part 28 after that.

DESCRIPTION OF SYMBOLS 1 Sensor system 2 Sensor sheet 3 Capacitance detection apparatus 4 Information processing apparatus 11 Dielectric layer 12A Front side electrode layer 12B Back side electrode layer 13A Front side wiring 13B Back side wiring 14A Front side connection terminal 14B Back side connection terminal 15A Front side protection layer 15B Back side protection layer 18 Adhesive layer 20 Voltage supply unit 21 Rectangular wave generation unit 22 First low-pass filter unit 23 Connection line 24 Connection line 25 Conversion unit 25a Operational amplifier 25b Resistive element 26 Filter unit 27 Rectification unit 28 Second low-pass filter unit 29 Output unit 40 Sensor system 41 Irradiation device 42 Photodetection device 46 Lighting control unit 47 Light receiving unit 50 Sample 50a Surface 55 Dust 60 Fluorescent lamp

Claims (8)

A capacitance detection device that detects a capacitance of a capacitance type sensor whose capacitance changes in response to an external input,
A voltage supply unit for applying a carrier voltage of a predetermined period to the capacitance type sensor;
A converter that converts a sensor output signal, which is a current signal output from the capacitive sensor in response to the application of the carrier voltage, into a voltage signal;
A rectifier that rectifies the sensor output signal converted into a voltage signal;
A low-pass filter that removes a frequency component of the carrier voltage included in the sensor output signal rectified by the rectifier;
A filter unit connected between the conversion unit and the rectification unit and allowing the sensor output signal to pass therethrough,
The filter unit is set such that a lower limit of a frequency band that allows passage of a signal component is higher than a frequency of environmental noise around the capacitive sensor,
The cutoff frequency of the low-pass filter unit is set higher than the frequency of the environmental noise,
The said conversion part is an electrostatic capacitance detection apparatus which converts the said sensor output signal into a voltage signal so that it may be proportional to the electrostatic capacitance of the said electrostatic capacitance type sensor. The capacitance type sensor is attached to a movable part of an object to be measured, and the capacitance type sensor is deformed according to the operation of the movable part, and the capacitance changes according to the deformation. 2. The capacitance detection device according to claim 1, wherein information indicating an operation state of a movable part of the object is output as a change in capacitance.   The capacitance detection device according to claim 1, wherein the frequency of the environmental noise is a frequency determined based on a frequency of a commercial power source.   4. The capacitance detection device according to claim 1, wherein the low-pass filter unit includes a second-order or higher-order low-pass filter. 5.   5. The capacitance detection device according to claim 1, wherein the filter unit includes a second-order or higher-order high-pass filter. The voltage supply unit
A rectangular wave generator for generating a rectangular wave of a predetermined period;
A filter unit that converts the rectangular wave into a signal wave that approximates a sine wave, and
The capacitance detection apparatus according to claim 1, wherein the signal wave is applied to the capacitance type sensor as the carrier voltage. A sensor system comprising a capacitance type sensor whose capacitance changes in response to an input from the outside, and a capacitance detection device that detects the capacitance of the capacitance type sensor,
The capacitance detection device is:
A voltage supply unit for applying a carrier voltage of a predetermined period to the capacitance type sensor;
A converter that converts a sensor output signal, which is a current signal output from the capacitive sensor in response to the application of the carrier voltage, into a voltage signal;
A rectifier that rectifies the sensor output signal converted into a voltage signal;
A low-pass filter that removes a frequency component of the carrier voltage included in the sensor output signal rectified by the rectifier;
A filter unit connected between the conversion unit and the rectification unit and allowing the sensor output signal to pass therethrough,
The filter unit is set such that a lower limit of a frequency band that allows passage of a signal component is higher than a frequency of environmental noise around the capacitive sensor,
The cutoff frequency of the low-pass filter unit is set higher than the frequency of the environmental noise,
The said conversion part is a sensor system which converts the said sensor output signal into a voltage signal so that it may be proportional to the electrostatic capacitance of the said capacitance type sensor. The capacitance type sensor is attached to a movable part of an object to be measured, and the capacitance type sensor is deformed according to the operation of the movable part, and the capacitance changes according to the deformation. 8. The sensor system according to claim 7, wherein information indicating an operation state of the movable part of the object is output as a change in capacitance.

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