JPH0678913B2 - Variable capacitance type sensor system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable capacitance type sensor system which is used for a pressure sensor or the like and detects a change in electric capacitance of a variable capacitance capacitor which operates as a transducer.

(Prior Art) For example, when controlling a refrigeration system mounted in an automobile, a device such as a pressure sensor that detects the refrigerant pressure, converts the refrigerant pressure into an electric signal, and outputs the electric signal to a control system is effective.

By the way, there is a pressure sensor that uses a silicon semiconductor for the diaphragm.However, such a pressure sensor cannot be used under harsh environmental conditions where the mounting conditions are harsh, such as in devices mounted in automobiles. There is a problem in durability and reliability.

Therefore, as a pressure sensor considered to be most suitable under such an environmental condition, there is a variable capacitance type transducer. This variable capacitance type transducer derives the amount of change as a capacitance change when the distance between two electrode plates forming a capacitor changes due to pressure or the like,
An electric signal is obtained by comparing this with a reference capacitor.

Therefore, when such a variable-capacity transducer is used as the pressure detecting means of the automobile refrigeration cycle described above, the detected pressure range is 100 kpa to 5 MPa, and the operating environment conditions are severe. It is necessary to perform signal processing with an electric circuit system provided at a position distant from the terminal. However, when the capacitance change is processed by an electric circuit system located away from the pressure detection terminal, the S / N ratio is extremely low, and there is a problem that an effective signal cannot be taken out.

Therefore, in order to overcome these problems, a signal processing system for effectively converting a capacitance change into a voltage signal in the vicinity of a pressure detection terminal of a transducer has been provided in the past, as disclosed in JP-A-62-267636. The configuration provided is adopted. That is, in the sensor disclosed in this publication, a variable capacitor is arranged on the lower surface of a ceramic substrate in the sensor, and a signal processing circuit for converting a capacitance change signal into a voltage on the upper surface of the substrate and an electric circuit for sensor calibration. Is arranged to compactly integrate them, and when a variable capacitor temporarily generates an electric signal in response to a physical quantity to be measured such as pressure, this electric signal is converted into a voltage by a signal processing circuit. The signal is converted into a signal, and the calibration electric circuit performs mutual calibration to obtain a voltage signal necessary for control.

FIG. 11 is a block diagram of the signal processing circuit shown in the above publication, and its outline will be described below. In FIG. 11, the reference capacitor Cp and the variable capacitance type capacitor Cv are connected in series, and the two terminals on the opposite side of the common node are two sets of potential sources, that is, the terminals on the opposite side of the common node of the reference capacitor Cp. For the potential sources E1 and E2, the terminals on the side opposite to the common node of the variable capacitance type capacitor Cv are the feedback potential source E3 and the potential source E4 which will be described later.
Can be switched by the changeover switches SW1 and SW2,
Further, the capacitance change signal of the variable capacitance type capacitor Cv with respect to the reference capacitor Cp derived from the common node is taken in in synchronization with the clock signal to the memory M via the cascaded three-stage inverter IN, and the output of this memory M is taken. It is integrated by the integrator I and converted into a voltage signal, and this voltage signal is divided by the voltage dividing circuit T to be fed back to the series circuit of both capacitors via the switch SW2, and the control signal is fed through the integrating amplifier A. It has gained. in this case,
The bypass switch SW3 connected in parallel to the changeover switches SW1 and SW2 and the first stage inverter IN on the common node side of the capacitor series circuit is a clock signal generation circuit CL composed of an oscillator O and a frequency divider DIV and a clock distribution. Switching control is performed by timing signals A, B, and C as shown in FIG. 12 obtained through the circuit CV, and data is taken in to the memory M in synchronization with the timing signal D. There is.

Therefore, by arranging an IC-compatible signal processing circuit with such a configuration and an electric circuit for sensor calibration in the immediate vicinity of the detection terminals such as the pressure sensor, a high-quality electric signal as a sensor output, that is, practicality Can be converted to a high range voltage.

(Problems to be Solved by the Invention) However, when the configuration in which the signal processing circuit and the calibration electric circuit are arranged in the vicinity of the detection terminal of the pressure sensor is used in an actual sensor system, it is not preferable in practical use. A new problem such as occurs.

That is, since the transducer is originally placed close to the measurement target, it is easily affected by the electromagnetic field of the environment to be measured. Therefore, in order to obtain a reliable signal, it is necessary to make the configuration less susceptible to electromagnetic influence from the measurement environment.

However, in the sensor system having the above-mentioned configuration, the reference capacitor and the variable capacitance type capacitor form a complicated arithmetic system in which the switches SW1 and SW2 are switched to one of two different power supply potentials. Since the pair of opposing electrodes of the transducer must be insulated from the part at the ground potential because they are operated at the intermediate potential state, stray capacitance is generated between the pair of electrodes and the measurement target, and the external electric field fluctuation It is easily affected and a discharge circuit is formed through the floating capacitance formed between the variable capacitance type capacitor and the ground. Therefore, the variable capacitance type capacitor is discharged through this discharge circuit, which causes a measurement error. is there.

The present invention provides a reliable variable capacitance type sensor system with high measurement accuracy by eliminating the influence of an external electric field and the discharge of the variable capacitance type capacitor due to the stray capacitance formed with the ground. With the goal.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a fixed capacitance capacitor, a variable capacitance capacitor that is connected in series to the fixed capacitance capacitor and operates as a transducer, and an input from a series connection of both capacitors. A comparator that detects the terminal voltage of one of the capacitors, a memory that captures the output of this comparator in synchronization with the clock signal, and a capacitor that integrates the output of this memory and that connects the two capacitors in series according to the output voltage. And an integrator that converts the voltage into a voltage proportional to the capacitance of the variable capacitor by charging or discharging the capacitor.

Further, in the variable capacitance type sensor system, a capacitor connected in series is connected to an integrator and is disconnected from the charge circuit and the integrator which are charged by the output voltage thereof, and a discharge circuit is formed. In addition, a switching means for periodically performing switching control is added.

Further, as another configuration of the variable capacitance type sensor system according to the present invention, a first capacitance capacitor and a second capacitance capacitor each having one end connected to the ground end of the power supply,
A charging circuit connected to the other ends of the first capacitance capacitor and the second capacitance capacitor to charge the first capacitance capacitor, and to transfer the electric charge of the first capacitance capacitor to the second capacitance capacitor. Switching means for performing switching control so that a parallel circuit and a discharge circuit for discharging the charge stored in the first capacitance capacitor and the second capacitance capacitor are sequentially and periodically formed, and the first capacitance capacitor by the switching means. And, when a parallel circuit of the second capacitance capacitor is formed, a comparator that detects the voltage generated in both capacitors at that time, a memory that captures the output of this comparator in synchronization with a clock signal, and an output of this memory When integrated and detected as a voltage inversely proportional to the first capacitance capacitor or proportional to the second capacitance capacitor To those that output voltage as a structure comprising an integrator providing when the charging circuit of the first capacitance capacitor is formed by said switching means.

(Operation) Therefore, in the variable capacitance type sensor system having such a configuration, when the terminal voltage of one of the capacitors is detected by the comparator in the series circuit including the fixed capacitance capacitor and the variable capacitance capacitor, the detection is performed. The voltage data when the value does not exceed the reference voltage is integrated by the integrator circuit and negatively fed back to the series circuit of both capacitors to stabilize the terminal voltage of one capacitor equal to the reference voltage and It is possible to detect as a voltage signal proportional to the capacitance change of the variable capacitor without configuring an arithmetic system, and it is practically possible to fixedly connect one end of the transducer to one end of the power supply. Stabilizes the sensor itself by shielding the sensor from external electric fields It is possible to achieve various operations and miniaturization at the same time. Further, the switching means is introduced and switching control is performed so that charge and discharge circuits are alternately formed for the fixed-capacitance capacitor and the variable-capacitance capacitor connected in series, so that the potential distribution is detected while always refreshing. Therefore, it is possible to obtain an output voltage that is directly proportional to the capacitance change of the variable capacitance capacitor without being affected by the leakage resistance between the capacitor terminals.

Further, in another configuration, the other ends of the first capacitance capacitor and the second capacitance capacitor, one end of which is connected to the ground end of the power supply, are switch-controlled to charge the first capacitance capacitor. Forming a charging circuit, a parallel circuit for commutating the charge of the first capacitance capacitor to the second capacitance capacitor, and a discharge circuit for discharging the charge of the first capacitance capacitor and the second capacitance capacitor sequentially and periodically. As a result, the voltage between the terminals of the first capacitance capacitor or the second capacitance capacitor when the parallel circuit of the first capacitance capacitor and the second capacitance capacitor is formed is detected by the comparator, and the detection signal is stored in the memory. If the output is integrated, the output voltage inversely proportional to the capacitance change of the first capacitance capacitor or proportional to the second capacitance capacitor is refreshed. It is possible to obtain while.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

First, the basic configuration of the variable capacitance type sensor system according to the present invention will be described with reference to FIG. In FIG.
CA and C _B are capacitors, one of which is fixed and the other of which is used as a variable capacitor. These capacitors C _A and C _B are connected in series and the terminals on the opposite side of the capacitors C _B and C _A connection side are connected to the power source. It is connected to ground potential. 10 is a voltage comparator (comparator) 10 which inter-terminal voltage V _B of the capacitor C _B is input, the comparator 10 and the threshold hold voltage V _R to a predetermined both terminal voltage V _B of the capacitor C _B By comparison, when V _B exceeds V _R , a low potential V _L is output when it does not reach a predetermined high potential V _H. 11 is a memory that stores the output V _C of the comparator 10 in synchronization with the clock pulse signal S _P , 12 is an integrating circuit that integrates the output V _D of this memory 11, 13 is the signal source impedance of the output voltage of the integrating circuit 12. by a buffer amplifier for decreasing the output voltage V _O obtained through the buffer amplifier 13 a capacitor C _a
Is fed back to the terminal on the side opposite to the C _B connection side of and is added to the output terminal t ₀ . Reference numeral 14 is a clock signal generator that gives a timing signal when data is taken into the memory 11, and this clock signal generator 14 includes a feedback resistor R _H and an input voltage holding capacitor C _H in a hysteresis input inverter as shown in the figure. It consists of a hysteretic oscillator connected.

Although the threshold voltage V _R is applied to the comparator 10 from the DC power supply in the above, a logic IC having a substantially constant threshold level may be used as the comparator.

Next, the operation of the variable capacitance type sensor system configured as described above will be described.

Assuming that the output V ₀ integrated by the integrating circuit 12 is applied to the capacitors C _A and C _B connected in series through the buffer amplifier 13, the potential distribution is V _A = V ₀ {C _B / (C _A + C _B )}, V _B = V ₀ {C _A / (C _A + C _B )}.

Now, if those inter-terminal voltage V _B of the capacitor C _B does not reach the threshold voltage V _R from the DC power source,
Polarity for increasing the output voltage V ₀ , that is, negative feedback is applied to the capacitors C _A and C _B connected in series, and V ₀ is stabilized under the condition of V _B = V _R.

Since C _A and C _B are connected in series, C _A V _A = C _B V _B , and V ₀ = V _A + V _B = V _A + C _A · V _A / C _B = V _A (1 + C _A / C _B ) = V _R (1 + C _A / C _B ).

Therefore, as is apparent from the above equation, one capacitor C _B is used as a transducer with a variable capacitance,
By using the other capacitor C _A as a reference capacitor having a constant electrostatic capacitance, one end of the transducer can be made to have the same potential as one end of the power supply voltage, and an output voltage directly proportional to the capacitance change of the transducer can be obtained. .

The above is the basic configuration of the sensor system, but in actual use, it is practically difficult to obtain a capacitor structure that can completely ignore the influence of leakage resistance between terminals as a capacitor. For this reason, when the applied voltage does not fluctuate or is slow with respect to the capacitors connected in series, the potential distribution of the series capacitors is ultimately dominated by the distribution ratio of the leakage resistance between the terminals. Therefore, it is practical to detect the potential distribution of the series capacitor while refreshing at a fast cycle.

FIG. 2 is a circuit configuration diagram showing an embodiment of the sensor system according to the present invention in consideration of such a point. In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Here, capacitors C _S and C connected in series are connected.
A circuit for refreshing _{Y at} a fast cycle will be mainly described. In other words, given a clock oscillator output signal S _P which is output from the clock pulse generator 14 to a clock pulse distributor 16 in the present embodiment, the electronic switch circuit 15 by the distributed pulse signal at the clock pulse distributor 16
The charging circuit for charging the series capacitors C _S and C _Y by the output voltage of the buffer amplifier 13 and the discharge circuit for discharging the same are alternately formed to refresh the series capacitors C _S and C _Y and distribute the potential distribution. Is to detect. Here, by providing Kurokuparusu signal S _P which is a clock pulse divider 16 is outputted from the clock pulse generator 14 as shown in FIG. 3 to the inverter through the delay circuit, together with obtaining a delayed signal 16b inverted,
A clock pulse signal _SP and an inverted delay signal 16b are obtained through a NAND circuit to obtain a signal 16c and its inverted signal 16d. The electronic switch circuit 15 includes four electronic switches S1 and S1 whose opening and closing are controlled by the pulse output from the pulse distributor 16.
2, S3, S4 are connected in series, one end of the electronic switch S1 is connected to the output end of the buffer amplifier 13, and one end of the electronic switch S4 is connected to the input end of the comparator 10. One end of the series circuit of the capacitors C _S and C _Y is connected between the electronic switches S2 and S3, and the other end is connected to the electronic switches S3 and S4.
And the capacitors C _A and
One end of the electronic switch S4 is connected between the connection with C _Y.

Next, the operation of the sensor system thus configured will be described.

Now, when the terminal voltage of the capacitor C _Y detected by the comparator 10 is taken into the memory 11 in synchronization with the rising edge of the clock pulse signal 16c output from the pulse distributor 16, the voltage data is stored in the integrating circuit 12 The output voltage V ₀ is derived from the output terminal t ₀ by the buffer amplifier 13 and is added to the electronic switch circuit 15. First, when the electronic switches S1 and S2 are simultaneously closed and the electronic switches S3 and S4 are opened, the capacitors C _S and C _Y are charged by the output voltage V ₀ obtained through the buffer amplifier 13. Also, one of the electronic switches S1 and S2 is opened,
When the electronic switches S3 and S4 are closed, a discharge circuit of the capacitors C _S and C _Y is formed, and the capacitors C _S and C _Y are discharged at the same time. Therefore, the electronic switch circuit 15
By pulsing so that the cycle of charging and discharging C _S and C _Y is sufficiently fast, the potential distribution is detected while ignoring the existence of leakage resistance between the terminals of capacitors C _S and C _Y. can do.

Therefore, if the capacitor C _Y is used as the transducer with variable capacitance and the capacitor C _S is used as the reference capacitor with constant capacitance, it is directly proportional to the capacitance change of the transducer without being affected by the leakage resistance between the capacitor terminals. The output voltage can be obtained. In this case, the output voltage V ₀ is given by V ₀ = V _R (1 + C _Y / C _S ).

When the capacitance of the variable capacitor as a transducer is constant and the capacitance decreases, the terminal voltage of this capacitor rises according to the principle of the electrostatic booster,
A comparator having this as an input operates to reduce the output of the integrator.

On the other hand, the terminal voltage of the series circuit of the variable capacity capacitor and the fixed capacity capacitor is the sum of the terminal voltage of each of the variable capacity capacitor and the fixed capacity capacitor. The electric charge corresponding to the above will flow out from this series capacitance circuit to the integrating circuit connected thereto. That is, discharge, which is the movement of electric charges, is performed from the series capacitance circuit.

Since the voltage of the integrator changes in the direction in which it is lowered by the operation of the comparator, the discharge from the series capacitance circuit continues until a new equilibrium point is reached.

In this way, the series capacitance circuit inputs and outputs electric charges through charging from the integrator and discharging to the integrator, and the terminal voltage corresponding to the electrostatic capacitance of the variable capacitance capacitor is uniquely determined.

The above describes the case where an output voltage proportional to the capacitance change of the transducer is obtained by using a variable capacitance capacitor that operates as a transducer and a fixed capacitance capacitor as a reference, but depending on the application, an output voltage that is inversely proportional to the capacitance change of the transducer may be used. Sometimes you want to get.

FIG. 4 shows another embodiment of the present invention when applied to such an application. The same parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted. Here, only different points will be described. .

In this embodiment, as shown in FIG. 4, a clock pulse oscillator
Given clock oscillation output signal S _P which is output from the 14 to the clock pulse distributor 18, the respective one end of the power supply end to the switching control of the electronic switch circuit 17 by a pulse signal distributed by the clock pulse distributor 18 2 commonly connected
The other end of each capacitor is switched and connected in the following form. That is, a charging circuit that charges one of the capacitors Ca by the output voltage of the buffer amplifier 13, and a parallel connection circuit that disconnects the charged capacitor Ca from the output end side of the buffer amplifier 13 and moves electric charge from the capacitor Ca to Cb. And these capacitors Ca, Cb
It can be switched to any one of the discharging circuits for discharging the charged electric charges. Here, the clock pulse distributor 18 supplies the clock pulse signal S _P output from the clock pulse oscillator 14 to the flip-flop circuit to obtain the output signal 18a and the inverted output of the flip-flop circuit as shown in FIG. Signal 1 obtained by ANDing the clock pulse signal S _P and the signal delayed by the delay circuit 1
8b and this signal 18b are further delayed by a delay circuit to obtain a signal 18c. The electronic switch circuit 17 is controlled to open / close by the pulse output from the pulse distributor 18 3
The electronic switches S5, S6, S7 are connected in series, one end of the electronic switch S5 is connected to the output end of the buffer amplifier 13, and one end of the electronic switch S7 is connected to one end of each of the capacitors Ca, Cb. And connected to one end of the power supply,
The input terminal of the comparator 10 is connected between the electronic switches S6 and S7.

Next, the operation of the sensor system having such a configuration will be described.

Now, when the capacitor Ca is in the discharged state, the pulse signal 18a output from the pulse distributor 18 closes the electronic switches S5 and S7 of the electronic switch circuit 17, and when S6 is opened, one capacitor Ca causes the buffer amplifier 13 Output voltage Vo
And the other capacitor Cb forms a discharge circuit to discharge the charge. Then electronic switch
When S6 closes and S5 and S7 open, one capacitor Ca
Is separated from the output terminal of the buffer amplifier 13, and at the same time, both capacitors Ca and Cb are connected in parallel and one capacitor Ca
The electric charge moves from the other capacitor Cb to the other capacitor Cb, and the voltage V _S generated in both capacitors Ca and Cb at that time is detected by the comparator 10. Then, after the voltages of the capacitors Ca and Cb are detected by the comparator 10, the capacitors Ca and Cb are discharged to prepare for the next circulation cycle. In this case, the stable state obtained by the above operation is represented by the following equation.

V ₀ Ca = V _S (Ca + Cb) = V _R (Ca + Cb) Therefore, V ₀ = (1 + Cb / Ca) V _R.

Therefore, the output voltage V ₀ inversely proportional to the variable capacitance of Ca can be refreshed by periodically performing the above-described switching control with the capacitor Cb as a fixed capacitance and Ca as the variable capacitance. Also, capacitors Ca and Cb
Since both of them can be directly connected to one end of the power supply, one end of the transducer is at the same potential as the one end of the power supply, which means that one side of the plate constitutes a shield against the external electric field of the internal circuit. Equivalent, and accurate and reliable measurement is possible without being affected by external noise. Furthermore, since Cb / Ca is a factor that determines the sensitivity, if Ca or Cb can be easily adjusted from the outside, there is a great advantage that the sensitivity can be appropriately changed.

According to this configuration, it is possible to obtain a great advantage that outputs proportional to or inversely proportional to capacitance changes can be arbitrarily selected as needed with the same circuit configuration in a state where exactly the same stability is compensated.

Next, the capacitors used in the variable capacitance type sensor system will be described.

There are various types of proximity sensors, but generally they have a fixed electrode 1a and a movable electrode 1b as shown in FIG. 6 with a simple and inexpensive structure, and the respective electrode surfaces are arranged facing each other. A known plate electrode capacitance type sensing structure, that is, a plate electrode capacitor 1 is known. In this plate electrode capacitor 1, the electrostatic capacitance C _w is C _w = K · S /, where S is the facing area, d is the facing distance, and K is the constant.
It is indicated by d and is inversely proportional to the facing distance d. Therefore, in the case where the movable electrode 1b is displaced in parallel to the fixed electrode 1a, that is, the facing area is changed, a capacitance change proportional to the moving amount of the movable electrode 1b can be obtained. To be However, in the case where the movable electrode 1a is moved in the direction of the facing distance d with respect to the fixed electrode 1b, the capacitance changes inversely in proportion to the movement of the movable electrode 1b. Therefore, if it is used as it is, the movable electrode 1b
The capacitance is not directly proportional to the amount of movement of
The change in the output voltage greatly deviates from the proportional relationship.

Therefore, in the present invention, even when the plate capacitor 1 is used as a sensor and the movable electrode 1b is changed in the direction of the facing distance d with the fixed electrode 1a, an output voltage almost proportional to the change of the distance d is obtained. It is the one.

FIG. 7 shows an example of the configuration of such a variable capacitance type sensor, in which a fixed capacitance capacitor C _F and a variable facing distance capacitor C _w are connected in series, and the combined capacitance of these two capacitors is used as the detection capacitor. It is configured to form C _Y.

The characteristic of the detection capacitor C _Y is C _Y = C _F {1-C _F / (C _F + C _W )} as shown in FIG. By comparing this characteristic with the graph showing the capacitance change with respect to the facing distance d in the lower part of FIG. 8, it is clear that the capacitance change of the variable capacitance type capacitor C _W with respect to the displacement reducing the distance from the constant distance d ₀ to d ₁ , So as to obtain an output voltage that is approximately proportional to the direction in which the output voltage is linearized, that is, the facing distance d.

Therefore, with the detection capacitor C _Y having such a configuration, it is possible to use a plate electrode capacitor in a usage pattern in which the distance between the facing electrodes is changed as a proximity sensor.

On the other hand, as shown in FIG. 9, in the case where the plate electrode capacitor 2 is composed of a disk-shaped thin plate and the end portion of the movable electrode 2b provided facing the fixed electrode 2a is fixed, When a uniformly distributed load P acts on the movable electrode 2b, the facing distance d of the movable electrode 2b with respect to the fixed electrode 2a changes due to the deflection. Therefore, if a variable facing distance type capacitor having such a configuration is connected in series with a fixed capacitance capacitor as shown in FIG. 7 to form the detection capacitor C _Y ,
The electrostatic capacitance between the movable electrode 2b and the fixed electrode 2a is as shown by the dashed line C _W ′ in FIG. So this curve
As is clear from C _W ′, since the linear variation increases with respect to the change in the distance d, an output voltage more proportional to the change in the facing distance of the facing distance variable capacitor can be obtained.

Furthermore, when the above-mentioned electrode plate capacitor is used as a variable capacitance type sensor under severe environmental conditions, the electrode plate structure has its own specific dimensions that change depending on the ambient thermal environment, so the electrode plate structure will not change depending on the ambient temperature. The capacitance tends to increase and decrease.

Therefore, in such a case, as shown in FIG. 10, a dielectric film 4 having a preferable temperature coefficient of permittivity is inserted between the fixed electrode 3a and the movable electrode 3b so as to change the capacitance with respect to the temperature change. Plate capacitor 3 configured to complement the component
And it is sufficient. In this case, it is already known that, as the dielectric film 4, for example, a polyethylene film has a temperature coefficient of −1500 ppm / ° C., and a polyethylene terephthalate film has a temperature coefficient of +400 ppm / ° C.
By inserting these films as a dielectric film between the fixed and movable electrodes, it is possible not only to complement the fluctuation of the ambient temperature but also to avoid the functional failure due to the short circuit of the fixed and movable electrodes. .

(Effects of the Invention) As described above, according to the present invention, it is possible to improve the measurement accuracy by eliminating the influence of the external electric field and the discharge of the variable capacitance type capacitor due to the stray capacitance formed with the ground. It is possible to provide a reliable variable capacitance type sensor system.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic configuration of a variable capacitance type sensor system according to the present invention, FIG. 2 is a circuit configuration diagram showing an embodiment of the present invention, and FIG. 3 is a switching timing of an electronic switch circuit of the same embodiment. 4 is a circuit diagram showing another embodiment of the present invention, FIG. 5 is a time chart showing the switching timing of the electronic switch circuit of the same embodiment, and FIG. 6 is the principle of the plate electrode capacitor. A configuration diagram for explaining
FIG. 7 is a circuit diagram showing a configuration example when a plate capacitor is used as a variable capacitance type sensor according to the present invention, FIG. 8 is a characteristic diagram of the variable capacitance type sensor according to the same configuration example, and FIG. 9 is a movable electrode. Schematic diagram of a plate capacitor with fixed edges
FIG. 10 is a block diagram of a plate electrode capacitor in consideration of means for correcting an error due to a change in ambient temperature, FIG. 11 is a circuit diagram showing a configuration of a conventional variable capacitance type sensor system, and FIG. 12 is a diagram explaining the operation of the system. It is a time chart for doing. 10 …… Comparator, 11 …… Memory, 12 …… Integrator circuit,
13 …… Buffer amplifier, 14 …… Clock signal generator, 1
5,17 ...... electronic switch, 16, 18 ...... Clock pulse _{divider, C A, C B, C} S, C Y, Ca, Cb ...... capacitor, 1-3 ...... Itakyoku capacitor.

Claims (3)

[Claims] 1. A fixed capacitance capacitor, a variable capacitance capacitor, one end of which is connected in series to the fixed capacitance capacitor, and the other end of which is connected to the ground end of a power source, and a variable capacitance capacitor which operates as a transducer. A comparator for detecting the terminal voltage of the variable capacitance capacitor, a memory for synchronizing the output of the comparator with the clock signal, and a memory for integrating the output of the memory and corresponding to the output voltage of the capacitors connected in series. A variable capacitance type comprising: an integrator that charges or discharges the variable capacitance to convert it into a voltage proportional to the capacitance of the variable capacitance capacitor; and an output terminal that outputs the output of the integrator as a detection output of the sensor. Sensor system. 2. A fixed capacitance capacitor, a variable capacitance capacitor, one end of which is connected in series to the fixed capacitance capacitor, and the other end of which is connected to the ground end of a power supply, which operates as a transducer. A comparator for detecting the terminal voltage of the variable capacitance capacitor, a memory for synchronizing the output of this comparator with a clock signal, and a memory for integrating the output of this memory and the capacitance of both capacitors connected in series by the output voltage. An integrator that converts the voltage into a voltage proportional to, a charging circuit that connects the series-connected capacitor to the integrator and charges the output voltage of the integrator, and a discharge circuit that is separated from the integrator and that forms a charging circuit. Switching means for periodically switching control to the discharge circuit, and the output of the integrator as the detection output of the sensor Variable displacement sensor system characterized by comprising an output terminal for output. 3. A first capacitance capacitor and a second capacitance capacitor each having one end connected to a ground end of a power source, and the first capacitance capacitor and the second capacitance capacitor connected to the other ends of the first capacitance capacitor and the second capacitance capacitor, respectively. A charging circuit for charging a first capacitance capacitor, a parallel circuit for commutating the charge of the first capacitance capacitor to the second capacitance capacitor, and discharging the charge of the first capacitance capacitor and the second capacitance capacitor. Switching means for performing switching control so that the discharging circuit to be sequentially formed is formed cyclically, and when the switching means forms a parallel circuit of the first capacitance capacitor and the second capacitance capacitor, both capacitors are then formed. A comparator that detects the voltage that occurs, a memory that captures the output of this comparator in synchronization with the clock signal, and an output of this memory The integrated circuit detects a voltage proportional to the first capacitance capacitor or inversely proportional to the capacitance of the second capacitance capacitor, and the output voltage thereof is formed by the switching means to form a charging circuit for the first capacitance capacitor. A variable-capacity sensor system comprising: an integrator that gives a time and an output terminal that outputs the output of the integrator as a detection output of the sensor.