JPH10142093A - Device and method for diagnosing capacitive sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a sure diagnosis by a simple operation by applying oscillation output, and inverted output to a pair of counter electrodes of a sensor element via a switching means. SOLUTION: An oscillation circuit 41 oscillates a frequency that is approximated to the center frequency component of an earthquake wave and applies it to one counter electrode 24 of a sensor element 16 through an analog switch 43. Also, after the phase of the oscillation output is inverted by 180 degrees by an inversion circuit 42, the output is fed to the other counter electrode 25 via an analog switch 44. But, in the case of an operation mode, the switches 43 and 44 are broken by breaking test terminals 19 and 21. On the other hand, the terminals 19 and 21 are connected at the time of self-diagnosis. Then, a timer 57 leads an H-level signal to a line 71 for a specific amount of time W1 after connection and enables the switches 43 and 44 to continue. Therefore, oscillation output and inverted output are fed from the circuit 41 to electrodes 44 and 45, thus a pendulum 23 can be surely deformed to making a sure diagnosis, and at the same time this procedure can be automated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device and method for a capacitance type sensor, and a diagnostic device for a gas pressure sensor.

[0002]

2. Description of the Related Art A capacitance type sensor is used for detecting an acceleration by constituting a seismic sensor for detecting an earthquake, and for detecting an inclination posture of a heating appliance such as a gas stove. ing. It is desired to check and diagnose whether such a capacitance type sensor operates normally. One underlying technology of a proposed invention for self-diagnosing a capacitive sensor is shown in FIG. The sensor element 1 is made of, for example, single-crystal silicon by an etching technique. A pair of opposed electrodes 3 and 4 are arranged on both sides in the displacement direction of a conductive pendulum 2 supported in a cantilever manner. When acceleration is applied to the sensor element 1, the pendulum 2 is displaced so as to approach one of the counter electrodes 3 and 4 and to move away from one of the other electrodes. The line 9 is connected to, for example, a +5 V DC power supply 11, and the line 8 is grounded.

The capacitance between the pendulum 2 and each of the opposing electrodes 3, 4 is a rectangular wave having a phase difference of 180 degrees from the oscillation circuit 7 to each of the opposing electrodes 3, 4 via lines 8, 9. The signal is provided, converted to a voltage by a conversion circuit 5 and derived on line 6. The output voltage on line 6 corresponds to the magnitude of the acceleration.

In order to diagnose the capacitance type sensor shown in FIG. 16, switches 12 and 13 such as push button switches which can be pressed by an operator are provided on each of the counter electrodes 3 and 4. Through these, + 5V
Is connected to the DC power supply 11 of FIG.

In diagnosing the capacitance type sensor, the sensor element 1 is kept stationary without applying acceleration,
The operator presses the switches 12 and 13 to conduct as shown in FIGS. 17A and 17B, respectively. The switch 12 is switched to the pulse p11 of FIG.
Conduction is performed as indicated by p12, and switch 1
By interrupting line 3, line 6 is changed to the state shown in FIG.
The pulse waveforms q11 and q12 shown in FIG. Also, by turning on the switch 13 as shown by the pulses p21 and p22 in FIG. 17 (2) and keeping the switch 12 off at this time, the line 6
The pulse waveforms q21 and q22 shown in (4) are obtained. The output voltage of line 6 is measured, for example, by digital voltmeter 1
By performing the measurement according to 4, it is possible to make a diagnosis and check whether the operation is performed normally.

[0006]

In one proposed technique shown in FIGS. 16 and 17, switches 12, 13 are provided.
Are simultaneously pressed and made conductive as shown by the pulse p13 in FIG. 17A and the pulse p23 in FIG. 17B, and the +5 V of the DC power supply 11 is applied to the opposing electrodes 3 and 4.
And therefore the pendulum 2 is not displaced. Therefore, self-diagnosis cannot be performed. The operator may determine that an abnormality has occurred because the output from the digital voltmeter 14 is not obtained despite the switches 12 and 13 being pressed simultaneously.

In the proposed technique, the switch 1
Since the switches 2 and 13 are operated by the operator, the conduction time and period are different. As a result, it is not possible to accurately know the aging of the sensor element 1 over a long period of time, for example, 10 to 20 years, simply by measuring the output voltage of the line 6 with the digital voltmeter 14.

In the proposed prior art, the output voltage of the DC power supply 11 is used as it is for diagnosis via the switches 12 and 13, and the output of the DC power supply 11 is also used for other components such as conversion. It is also used for the circuit 5, the oscillation circuit 7, and the like. Therefore, its DC power source 1
If the output voltage of the line 1 fluctuates, the output voltage of the line 6 will change. Therefore, accurate diagnosis becomes impossible.

Further, in the proposed technique, when the voltage of the line 6 is measured by a digital voltmeter, the time for which the switches 12 and 13 are turned on is determined by the digital voltmeter 1.
It is necessary to set the time sufficiently longer than the voltage sampling period of No. 4. 17 (3) and FIG.
As shown in (4), the rising and falling edges of the pulse waveforms q11 and q12; q21 and q22 of the output voltage on line 6 include overshoot and undershoot waveforms, and thus the conduction time of switches 12 and 13 However, when the sampling period is shorter than the sampling period of the digital voltmeter 14, the voltage measurement result may include a large error.

Therefore, in the above-mentioned proposed technique, there is a problem that the skill of the operator is required in order to diagnose the capacitance type sensor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a diagnostic device and method for a capacitive sensor and a diagnostic device for a gas pressure sensor which are easy to operate and can perform accurate diagnosis. is there.

[0012]

According to the present invention, there is provided (a) a sensor element comprising a conductive pendulum which is supported at one end and has elasticity, and a pair of pendulums which are arranged at both sides in the displacement direction of the pendulum. (B) capacitance detecting means for detecting the capacitance between the pendulum and each counter electrode, and (c) deriving an output of a predetermined frequency to one of the counter electrodes. An oscillation circuit for inverting the oscillation output, and an inversion circuit for inverting the oscillation output to the other counter electrode; and (e) switching means for supplying / cutting off the oscillation output and the inverted output to each counter electrode. This is a diagnostic device for a capacitance type sensor. The present invention also provides (a) a sensor element, which comprises a conductive pendulum that is supported at one end and has elasticity, and a pair of opposing electrodes disposed on both sides in the displacement direction of the pendulum. (B) capacitance detecting means for detecting the capacitance between the pendulum and each counter electrode, (c) an oscillation circuit for deriving an output of a predetermined frequency, and (d) an output of the oscillation circuit. A diagnostic device for a capacitive sensor, comprising: a switching unit that shuts off and applies the output to one counter electrode; and (e) an inversion unit that inverts the output of the switching unit and applies the output to the other counter electrode. is there. The present invention also provides (a) a sensor element, which comprises a conductive pendulum that is supported at one end and has elasticity, and a pair of opposing electrodes disposed on both sides in the displacement direction of the pendulum. (B) capacitance detection means for detecting the capacitance between the pendulum and each counter electrode; (c) oscillation means for deriving an output of a predetermined frequency; and (d) output of the oscillation means. A diagnostic device for a capacitive sensor, comprising: a pair of switching elements interposed between electrodes; and (e) control means for alternately turning on / off the switching means. According to the present invention, the switching means is set to a cutoff state at the time of a normal measurement for measuring an acceleration or a tilt angle without performing a diagnosis, and is set to a conductive state at the time of performing a diagnosis. When the switching means is cut off, if an acceleration acts on the sensor element due to an earthquake or the like, the cantilevered pendulum is elastically deformed and bent by the acceleration, and the pendulum and one of the pair of counter electrodes are bent. Are shorter, and the distance to one of them is longer. Thus, the capacitance detecting means can detect the capacitance between the pendulum and each of the opposing electrodes, determine the change in the distance between the electrodes, and detect the applied acceleration.
The sensor element is fixed to the measurement object, and the measurement object,
Therefore, even when the sensor element is inclined at a certain angle,
The pendulum is elastically deformed, and the inclination angle can be measured in the same manner as described above. When performing self-diagnosis of a capacitance type sensor including a sensor element and a capacitance detecting means, an oscillation output of a predetermined frequency from an oscillation circuit is applied to one counter electrode, and the oscillation output is inverted by an inversion circuit. To the other counter electrode, whereby either one of an electrostatic attraction force or an electrostatic repulsion force acts between the pendulum and the one counter electrode, and the other between the pendulum and the other counter electrode. Works. As a result, the capacitance detecting means can determine the change in the distance between the electrodes, and can diagnose whether or not the operation is performed normally. By intermittently supplying and blocking the oscillation output and the inverted output to each counter electrode by the switching means, it is possible to diagnose the repetitive operation of the elastic bending deformation to both sides of the pendulum. Furthermore, according to the present invention, an oscillation output and its inverted output are simultaneously applied to each pair of counter electrodes, so that the electrostatic force acting on the pendulum is twice as large as the electrostatic force in the above-mentioned proposed technology. A force can be applied, the displacement of the pendulum can be increased, and the measurement accuracy of diagnosis can be improved. As described above, since the signal applied to each counter electrode is an oscillation output and an inverted output obtained by inverting the oscillation output and shifting the phase by 180 degrees, it is impossible that the signals applied to each of the pair of counter electrodes have the same phase at the same time. Absent. As a result, the pendulum can be flexibly deformed, and the diagnosis can be reliably performed.
This also makes it possible to automate the diagnosis.

Further, the present invention is characterized in that power is supplied to an oscillation circuit and an inversion circuit from a constant voltage source using a shunt regulator. According to the present invention, the components for performing diagnosis, that is, the oscillation circuit and the inversion circuit, are supplied with power from a constant voltage source using a shunt regulator, whereby the operations of the oscillation circuit and the inversion circuit are controlled by the power supply. Stable operation can be maintained irrespective of fluctuations in voltage and the like. For example, the output voltage waveform of the oscillation circuit is stabilized. Further, the operation of the inverting circuit is stably maintained. Therefore, the output of the sensor element at the time of diagnosis and the measurement accuracy of the capacitance detecting means can be improved. The frequency of the oscillation output of the oscillation circuit is also stabilized. This also makes it possible to detect long-term aging of the sensor element, for example for 10 to 20 years.
In particular, since the constant voltage source uses a shunt regulator as described above, that is, stabilizes the output voltage by current control, it particularly stabilizes the operation of components including an oscillation circuit and an inversion circuit used for diagnosis. It becomes possible.

Further, according to the present invention, the frequency of the oscillation circuit is about 2
４００400 Hz. Further, according to the present invention, the frequency of the oscillation circuit is about 2 to about 10 Hz.
It is characterized by the following. According to the present invention, the oscillation frequency is set to about 2 to 400 Hz, preferably about 2 to about 10 Hz, and thus includes a signal around the center frequency component 2-5 Hz of the seismic wave at the time of the occurrence of the earthquake. This makes it possible to diagnose the operation in the actual use state. Further, a shock wave generated when the object collides with the measurement target is, for example, around 10 Hz, and even in such an application, it is possible to make a diagnosis in a state of use.

Further, the present invention is characterized in that the oscillation output of the oscillation circuit is a rectangular wave and the duty is 1. According to the present invention, the oscillation output waveform is a rectangular wave, and a configuration using an integrated circuit or the like of the oscillation circuit can be easily realized. When making a diagnosis using this rectangular wave, the output waveform between the pendulum of the sensor element and the counter electrode, and thus the output waveform of the capacitance detecting means, includes portions of overshoot and undershoot. The diagnostic accuracy can be improved for two reasons. The first reason is that the signal given to the pair of counter electrodes as described above is:
The oscillation output and its inverted output, the pendulum can obtain a large deflection displacement amount, for example, twice as compared with the above-mentioned proposed technique, and thus the emission value of the overshoot and undershoot portions is This is because the ratio can be made smaller than the peak-to-peak value corresponding to the amount of displacement of the pendulum, and the overshoot and undershoot portions that cause noise can be reduced. The second reason is that when using a digital measuring means such as a digital voltmeter for measuring a physical quantity such as a voltage corresponding to the distance between the pendulum of the sensor element and the counter electrode, such a digital measuring means is analog / digital And a digital / analog converter. The sampling frequency is, for example, 500 to 1
000 Hz, or even higher. Compared to this, the frequency of the oscillation circuit is about 2 to about 400
By setting the oscillation frequency in the range of Hz,
This is because the value is set to a value sufficiently lower than the sampling frequency, whereby the measurement error of the digital measuring means due to the occurrence of overshoot and undershoot can be reduced. Furthermore, according to the present invention, in order to make the duty of the square wave equal to 1, each half cycle of the oscillation output is made equal, thereby reducing or eliminating the measurement error caused by the response speed of the pendulum of the sensor element. Can also improve the accuracy of the measurement and thus the diagnosis.

Further, the present invention is characterized in that the pendulum of the sensor element is made of conductive single crystal silicon. According to the present invention, since the pendulum is formed of conductive single-crystal silicon, it can function as a completely elastic body without hysteresis, brittleness, and grease, and can improve measurement accuracy and can have cracks and the like. Can be prevented. Further, such a pendulum made of single-crystal silicon can utilize the manufacturing technology for a silicon wafer as it is, and therefore, for example, a sensor of the order of several mm can be manufactured in large quantities with high quality.

According to the present invention, a sensor element is provided. The sensor element is provided with a conductive pendulum which is cantilevered and has elasticity, and a pair of opposed electrodes which are arranged at both sides in the displacement direction of the pendulum. A sensor element having an oscillation output having a predetermined frequency of the oscillation circuit to one counter electrode, an inverted signal obtained by inverting the output of the oscillation circuit to the other counter electrode, and a pendulum and each counter electrode. And diagnosing the sensor element by detecting the capacitance between the two. Also, according to the present invention, the output of the oscillation circuit is about 2 to about 400 Hz.
It is characterized by the following. Further, according to the present invention, the oscillation output of the oscillation circuit is a square wave,
The duty is one. ADVANTAGE OF THE INVENTION According to this invention, even an unfamiliar person who does not receive training for a diagnosis can perform a diagnosis with high accuracy by simple operation exactly.

The present invention also provides (a) a gas pressure sensor, which is a casing forming a measurement space into which a gas whose gas pressure is to be measured is introduced, and faces the measurement space and is elastically deformed in accordance with the gas pressure. A gas pressure sensor having a conductive diaphragm and a counter electrode arranged at a distance in the direction of displacement of the diaphragm; (b) capacitance detecting means for detecting a capacitance between the diaphragm and the counter electrode; and (c) An oscillation circuit for deriving an oscillation output of a predetermined frequency and applying the oscillation output between the diaphragm and the counter electrode; and (d) switching means for supplying / cutting off the oscillation output applied between the diaphragm and the counter electrode. This is a diagnostic device for a gas pressure sensor.

Further, the invention is characterized in that the diaphragm of the gas pressure sensor is made of conductive single crystal silicon. According to the present invention, with the switching means shut off,
With the conductive diaphragm elastically deformed according to the gas pressure introduced into the measurement space of the gas pressure sensor, a physical quantity such as a voltage corresponding to the pressure can be derived from the capacitance detecting means. By conducting the switching means, the output of the oscillation circuit is applied between the diaphragm and the opposing electrode facing the diaphragm, and highly accurate diagnosis can be performed by a simple operation.

[0020]

FIG. 1 is an electric circuit diagram showing the entire configuration of an embodiment of the present invention. For example, in a seismic sensor provided in a gas meter or the like, a sensor element 1
6 detects the acceleration of the seismic wave, shuts off the electromagnetic valve 17 interposed in the gas passage when the earthquake occurs, and displays the occurrence of the earthquake by the display means 18. In order to perform self-diagnosis of the sensor element 16 and its related components, the operator sets the self-diagnosis mode by connecting a conducting wire 21 between the pair of test terminals 19 and 20, and displays the measurement result on display means. 18 and the output voltage is measured by measuring means 22 such as a digital voltmeter.

The sensor element 16 includes a conductive pendulum 23,
The pendulum 23 has a pair of opposing electrodes 24 and 25 which are arranged at both sides in the displacement direction (vertical direction in FIG. 1) of the pendulum.
The pendulum 23 is supported by one shoulder, can be bent with elasticity, and is conductive.

The capacitance detecting means 26 has a capacitance / voltage conversion function of drawing out a voltage corresponding to the capacitance between the pendulum 23 and each of the counter electrodes 24 and 25 to a line 27. In order to achieve this capacitance / voltage conversion function, an oscillation circuit 28 is provided, and a high-frequency signal is applied to each of the counter electrodes 24 and 25 via coupling capacitors 29 and 30 to detect the capacitance. A bridge is configured. Oscillation circuit 28
From the counter electrode 24 via the coupling capacitors 29 and 30
The signals provided to 25 have a phase difference of 180 degrees from each other. The counter electrode 24 is grounded via a resistor 31, and the other counter electrode 25 is connected to a line 33 via a resistor 32, and is supplied with power having a voltage of, for example, + 5V.

Assuming that the capacitance between the pendulum 23 and each of the counter electrodes 24 and 25 is C1 and C2, C1 = C2 in a natural state where no acceleration is present. And each counter electrode 24, 25
Are different from each other, which results in C1 <C2 or C1> C2. Capacitance detection circuit 26
Sets the capacitance between the pendulum 23 and the counter electrode 24 to C1
When the capacitance between the pendulum 23 and the other counter electrode 25 is C2, the capacitances C1, C2
Are represented by the following equations.

[0024]

(Equation 1)

The capacitance detecting means 26 derives a voltage V3 depending on the capacitances C1 and C2 on a line 27.

[0026]

(Equation 2)

Here, the composite value (C1-C2) / (C1 + C
2) is proportional to the acceleration applied to the sensor element 16.

The capacitance detecting means 26 led out to the line 27
Is supplied to a low-pass filter 35. The low-pass filter 35 filters and selectively derives a signal having a center frequency component of the seismic wave of about 2 to about 10 Hz, and preferably filters and selectively derives a signal of about 2 to 5 Hz. This selectively derives only seismic waves, for example, about 10
Blocks shock waves around Hz. Thus, the cutoff frequency f0 of the low-pass filter 35 is determined.

The determination circuit 36 responds to the output of the low-pass filter 35 and, when an output of the low-pass filter 35 exceeding a predetermined discrimination level is obtained, an electromagnetic valve interposed in the pipe for supplying gaseous fuel. At the same time, a warning is issued by operating the display means 18 such as a display lamp and a buzzer.

The oscillation circuit 28 calculates the voltage V3 corresponding to the capacitances C1 and C2 by the capacitance
And a bridge for obtaining the voltage V3 corresponding to the capacitances C1 and C2 may be formed.

The DC power of the power source 37 is supplied from the constant voltage circuit 38 to the line 33, and is supplied to the oscillation circuit 28 and the capacitance detecting means 26.
Is applied to the counter electrode 25.

The output of the power supply 37 is also supplied from another constant voltage circuit 39 to the electric circuit 40. The electric circuit 40 includes an oscillation circuit 41 for self-diagnosis and an inversion circuit 4.
2 and analog switches 43 and 44. The oscillating circuit 41 includes an operational amplifier 45, a resistor 46, and a capacitor 47, generates a rectangular wave having a duty of about 1 to about 400 Hz, particularly preferably about 2 to 10 Hz, and still more preferably about 2 to 10 Hz. It is set to 2 to about 5 Hz. Thus, the frequency of the oscillation circuit 41 has a frequency approximating the center frequency component of the seismic wave. The oscillation output of the oscillation circuit 41 is supplied from the line 48 via the analog switch 43 to one counter electrode 24 from the line 49. The oscillation output of the line 48 is inverted by the inverting circuit 42, and is supplied from the line 50 to another counter electrode 25 via the analog switch 44. Thus, the oscillation circuit 41 and the inversion circuit 4
2 and the analog switches 43 and 44 are connected to a constant voltage circuit 39.
Is supplied.

The test terminal 19 is connected to a line 51 connected to the above-described line 33 via a diode 52 and a resistor 53, and is grounded via a capacitor 54. Another test terminal 20 is grounded. Resistance 53
The capacitor 54 and the anode of the diode 52 are connected to a connection point 55. The output of the connection point 55 is supplied to the operational amplifier 56, amplified, and supplied to the timer 57. The output of the timer 57 is supplied to the analog switches 43 and 44.
As an on / off control signal. In the state where the self-diagnosis is not performed and the test terminals 19 and 20 are cut off, the voltage of the connection point 55 is changed to the line 51,
At this time, the output of the operational amplifier 56 is at the H level, the output of the timer 57 remains at the L level, and the analog switches 43 and 44 are kept off. Therefore, the operation mode is such that acceleration such as seismic waves can be detected.

When performing self-diagnosis, the test terminal 1
9 and 20 are connected by a conductor 21, for example, a conductor. As a result, the electric charge of the capacitor 54 is discharged through the diode 52 and the conductor 21, and the connection point 55 is set to the grounded L level. As a result, the output of the operational amplifier 56 becomes L level,
Supplies a signal in which the H level and the L level are alternately repeated for a predetermined time W1 (for example, about 1 second) to the analog switches 43 and 44, and turns on / off the analog switches 43 and 44.

FIG. 2 is an electric circuit diagram showing a specific configuration of the constant voltage circuits 38 and 39. A DC voltage of, for example, +8 V from the power supply 37 is applied to a line 58, and capacitors 59 and 60 are applied to a three-terminal regulator 61a connected to an input and an output, respectively, for stabilization. Thus, a voltage of +5 V is derived. The power applied to line 51 is
And to the timer 57.

The power supplied from power supply 37 to line 58 is also supplied to the collector of control transistor 61b of constant voltage circuit 39. A resistor 62 is connected between the collector and the base of the transistor 61b, and a shunt regulator 63 is connected to the base between the resistor 62 and the ground. The control terminal 64 of the shunt regulator 63 is supplied with the output voltage of the line 65 divided by the resistors 66 and 67. Control terminal 64 and control transistor 61b
A capacitor 68 for blocking noise
Is connected. The line 65 is also connected with a capacitor 69 for smoothing. Line 65 is the electrical circuit 40
Connected to. The shunt regulator 63 has a function of flowing a base current of the control transistor 61b in accordance with a control voltage given from the control terminal 64. When the voltage of the line 65 changes, the base current of the control transistor 61b decreases. , Its control transistor 6
1b, the collector-emitter impedance becomes large, which causes the voltage on line 65 to rise
Is maintained at a constant value corresponding to the control voltage determined by This constant voltage circuit 39 is a shunt regulator 63
And the current is used to stably maintain the impedance of the control transistor 61b, so that a highly stabilized voltage can be accurately applied to the line 65 without depending on the voltage supplied from the power supply 37 to the line 58 and without depending on the temperature. Is derived.

When power is supplied from the constant voltage circuit 38 to the oscillation circuit 28 via the line 33, the oscillation circuit 28 is connected to the pendulum 23 of the sensor element 16 and the counter electrode 2.
In order to derive a voltage V3 corresponding to each capacitance between 4 and 25 on the line 27, the oscillation operation is performed as described above. Voltage waveforms applied to the coupling capacitors 29 and 30 of the oscillation circuit 28 are as shown in FIGS. 3A and 3B, respectively. Signal waveforms for detecting the capacitances applied to these coupling capacitors 29 and 30 have a phase difference of 180 degrees from each other.

FIG. 4 is a waveform chart for explaining the operation of the embodiment shown in FIGS. FIG. 4 (1)
6 shows an oscillation output waveform derived on a line 48 of the oscillation circuit 41. In this embodiment, the oscillation frequency is, for example, 2.5 Hz, the duty is 1, 0 V and 3
V of each level. The signal waveform applied from line 48 to one analog switch 43 is as shown in FIG. 4C, and the signal inverted by inverter circuit 42 and applied to analog switch 44 is shown in FIG.
It has the waveform shown in (2). When the self-diagnosis is not performed, the test terminals 19 and 20 are open as shown in FIG. 4 (4), that is, are not connected by the conductor 21, and when the self-diagnosis is performed, the test terminals 19 and 20 are not connected.
20 are connected by a conductor 21 and closed. The timer 57 derives a high-level signal on the line 71 from the time t1 at which the test terminals 19 and 20 are turned on by the conductor 21 to a time t2 after a predetermined time W1 has elapsed. 43,4
4 is conducted. Therefore, the counter electrodes 24 and 25 include
An oscillation output and an inverted output via the analog switches 43 and 44 are provided. As a result, the detection signal shown in FIG. In this embodiment, the peak-to-peak value V4 of the detection signal on line 27 is, for example, 200 mV,
This corresponds to, for example, an acceleration of 200 Gal. The determination circuit 36 detects the voltage V4 and performs level discrimination, thereby determining that the sensor element 16 is normal. When the voltage V4 cannot be obtained, it can be determined that the sensor element 16 is abnormal. Further, the output voltage on line 27 can be measured, for example, by digital voltmeter 22. When no acceleration is present, the capacitance detecting means 26 derives an output voltage of 2.5 V, and outputs the voltages of 2.5 V to 5 V and 2.5 to 0 V in accordance with the acceleration in accordance with the acceleration. Derive.

In the above embodiment of the present invention, by turning on the two analog switches 43 and 44 at the same time, the counter electrodes 24 and 25 have the oscillation output and the inverted output whose phase is shifted by 180 degrees. Since the output is supplied, the signals supplied to the respective counter electrodes 24 and 25 do not have the same phase at the same time. As a result, the pendulum 23 can be flexibly deformed, and the diagnosis can be made sure and the diagnosis can be automated.

The electric circuit 40 is supplied with electric power having a stabilized high-precision voltage from the constant voltage circuit 39 independent of the temperature via the line 65 to the electric circuit 40.
1. Therefore, the frequency and voltage of the voltage applied to the counter electrodes 24 and 25 from the analog switches 43 and 44 are stabilized with high accuracy. Therefore, it is also possible to detect the aging of the sensor element 16 over a long period of time, for example, 10 to 20 years. By setting the oscillation frequency of the oscillation circuit 41 to, for example, the center frequency component of a seismic wave at the time of the occurrence of an earthquake as described above, an excellent effect that diagnosis can be performed during the seismic wave detection operation of the present device is achieved. You.

Furthermore, since the oscillation circuit 41 generates a rectangular wave as described above, it can be easily realized using an integrated circuit or the like. When this rectangular wave is applied to the opposing electrodes 24 and 25 as described above, the signal waveform led out to the line 27 of the capacitance detecting means 26 is, as shown in FIG. Although the embodiment includes the chute 74, the accuracy of the diagnosis can be improved in the embodiment of the present invention. The reason for this is that the voltage that changes up and down the potential of the pendulum 23 is periodically applied to the opposing electrodes 24 and 25 by the operation of the oscillation circuit 41 and the inverting circuit 42, so that the pendulum 23 has a large deflection displacement. This is because the amount of overshoot and undershoot can be obtained compared to the peak-to-peak value V4 of the voltage.
This is because the ratio of the voltages V5 and V6 of 74 (that is, V5 / V4 and V6 / V4) can be made relatively small. Further, by setting the oscillation frequency of the oscillation circuit 41 to, for example, about 2 to 400 H as described above, it is sufficiently lower than the sampling frequency of the commercially available digital voltmeter 22, for example, 500 to 1000 Hz or more. Thus, the voltage measurement error due to the overshoot and undershoot portions 73 and 74 can be reduced.

The waveform of the oscillation output led out to the line 48 of the oscillation circuit 41 may be, for example, a sine wave as shown in FIG. The section may be a rounded trapezoidal wave.

FIG. 8 is a sectional view of the sensor element 16.
FIG. 9 is a perspective view showing the sensor element 16 with a part cut away. The sensor 16 includes a pendulum 23 that is supported in a cantilever manner, and a pair of electrodes 24 and 25 that are arranged on both sides of the pendulum 23 in a direction in which the pendulum 23 reciprocates (vertical direction in FIG. 8). The pendulum 23 includes a pendulum main body 118 and a cantilever support portion 119, and the cantilever support portion 119 is connected to the mounting portion 120. The pendulum 23 and the mounting part 120 are
It is made of conductive single crystal silicon. The spacer 121 is arranged so as to face the pendulum main body 118. The electrodes 24 and 25 are formed on flat glass plates 122 and 123. The electrodes 24 and 25 are thin films made of aluminum, and are formed by, for example, a method such as vapor deposition. Glass plate 122,1
23 is a substrate 124, 1 made of conductive single crystal silicon
The electrodes 24 and 25 are connected to connection holes 126 and 127 formed in the glass plates 122 and 123, respectively.
Are electrically connected to the substrates 124 and 125 via the. Thus, the sensor 16 is configured symmetrically with respect to the symmetry plane 128 of FIG. Since the cantilevered support portion 119 is a completely elastic body, no hysteresis, brittleness and creep occur. Mounting part 120, glass plates 122 and 123, and substrate 1
24, 125 are completely fused via silicon dioxide, as are the spacers 121, so that the interior space 129 is airtight and evacuated. Distances d1 and d2 between pendulum body 118 and electrodes 24 and 25
Is about 2 to 5 μm in a natural state, that is, in a state where no acceleration is acting. In this embodiment, d1 = d2
It is. The spacer 121 is made of the same material as the pendulum 23 and the mounting portion 120. Thus, the sensor 16 is, for example, 4 × 4.5 × 3 mm in thickness, and is formed in a minute shape.

The characteristics of such a sensor 16 are stable over a long period of time, and it is possible to detect acceleration with high accuracy in a wide temperature range of -40 to + 125 ° C. Since the sensor 16 is symmetrical with respect to the plane 28 and therefore expands uniformly as a whole due to thermal expansion, the combined value of the capacitance of the pendulum body 118 and each of the electrodes 24 and 25 does not change. The sensor 16 detects the over-impact of, for example, about 4000 g (g is the gravitational acceleration), that is, the swing of the pendulum main body 118 due to the over-acceleration.
5, that is, by limiting with the glass plates 122 and 123,
No excessive flexing force acts on the cantilever support portion 119 supporting the pendulum body 118, and therefore the cantilever support portion 1
19 can be prevented from being damaged. Further, according to the configuration of this embodiment, the selectivity in the sensitivity direction is excellent. That is, pendulum 2
Since the sensor 16 includes the layered structure in the vertical direction in FIG. 8, the sensitivity is excellent in the vertical direction in FIG. 8, and the sensitivity in the direction perpendicular to the paper of FIG. 8 is extremely low.

Further, the pendulum 23 and the mounting portion 120
The microfabrication is easy by the semiconductor etching technology, the quality can be stabilized and the price can be reduced by the mass production effect by greatly reducing the number of manufacturing steps by automating the sensor 16. In addition, since the sensor 16 can be manufactured by the silicon wafer technology and has a very low temperature coefficient, the sensor 16 can be adjusted and shipped at room temperature, thereby greatly reducing the number of manufacturing steps. In addition, a micro-etching technique can be adopted, and miniaturization can be achieved.

FIG. 10 is an overall electric circuit diagram of another embodiment of the present invention. In this embodiment, the above-described FIGS.
And the corresponding parts are denoted by the same reference numerals. It should be noted that in this embodiment, an analog switch 76 is interposed in the line 48 from which the output of the oscillation circuit 41 is derived. The output of the analog switch 76 is applied to the counter electrodes 24 and 25 via a line 49 and from the inverting circuit 42 via a line 50, respectively. The analog switch 76 has the same configuration as the analog switches 43 and 44 described above. According to such an embodiment, the self-diagnosis of the present apparatus can be performed in the same manner as in the above-described embodiment.

In the embodiment shown in FIGS. 1 to 9, since two analog switches 43 and 44 are used, if any one of the analog switches 43 and 44 breaks down, it remains disconnected. In this case, the capacitance detecting means 26 derives half of the output waveform (= V4 / 2) shown in FIG. 4 (6) on the line 27, whereby one of the analog switches 43 and 44 fails. You can easily know that you are.

FIG. 11 is an electric circuit diagram showing the entire configuration of another embodiment of the present invention. This embodiment is similar to the above-described embodiment, and corresponding portions are denoted by the same reference numerals. The control signal derived from the timer 57 to the line 71 is directly supplied to the analog switch 43, and the control signal is inverted by the inverting circuit 77 and supplied to the other analog switch 44. Other configurations are the same as those of the embodiment shown in FIGS. Also in this embodiment, the self-diagnosis of the present apparatus can be performed automatically.

FIG. 12 is an electric circuit diagram showing a gas pressure sensor diagnostic device 77 according to another embodiment of the present invention. In the gas pressure sensor 78, a gas whose gas pressure is measured is introduced into a casing 80 forming a measurement space 79 via a pipe 81. The conductive diaphragm 82 elastically deforms according to the gas pressure in the measurement space 79. A pair of opposing electrodes 83, 8 are spaced apart in the direction of displacement of diaphragm 82 (vertical direction in FIG. 12).
4 are arranged. Signals having a phase difference of 180 degrees from each other are supplied from the oscillation circuit 28 to the respective counter electrodes 83 and 84 via the coupling capacitors 29 and 30. Diaphragm 8
2 is supplied to the capacity detecting means 26 via a line 85, and the output via the line 27 is supplied to a control circuit 86. When the pressure becomes lower than a predetermined value and when the pressure becomes higher than a predetermined value. When it becomes abnormally large, a signal is issued and visual or acoustic display is performed by the display means 18, and the electromagnetic valve 17 is shut off. Line 27
Can be measured by the digital voltmeter 22, for example. Parts corresponding to the above-described embodiment of the embodiment of the present invention shown in FIG. 12 are denoted by the same reference numerals.

An oscillation circuit 41 and an operation switch 87 are provided to enable automatic diagnosis of the apparatus. The output of the oscillation circuit 41 is connected to one counter electrode 83 from a line 88 via an operation switch 87.

FIG. 13 is a sectional view of the gas pressure sensor 78, and FIG. 14 is a plan view of the gas pressure sensor 78. The gas pressure sensor 78 includes a diaphragm 82 formed of conductive single crystal silicon or the like, and a counter electrode 8 formed on almost the entire surface of a glass substrate 89 by aluminum evaporation or the like.
3, 84, and a spacer 90 made of a glass plate or the like for keeping a constant gap between the diaphragm 82 and the counter electrodes 83, 84. The diaphragm 82 is, as shown in FIG.
An extremely thin deformed film is formed at the center of a rectangular substrate having a certain thickness by etching or the like. A silicon plate 91 is adhered on the diaphragm 82 to form a measurement space 79. A through hole 92 communicating with the measurement space 79 is formed. The fluid pressure to be measured is introduced into the measurement space 79.

The glass substrate 89 on which the counter electrodes 83 and 84 are formed is bonded on an electrically insulating substrate made of ceramic or the like. Surface of glass substrate 89 and spacer 90
Of the diaphragm 82 is connected to the counter electrode 8
3, 84 are formed so as not to be short-circuited. The above-described silicon and glass are bonded by heat fusion or the like, and the outer shape of the gas pressure sensor 78 is, for example, 4 mm × 4.5 mm × 3.
mm.

Next, the operation will be described. At the time of pressure measurement, the switch 87 is shut off. When the gas to be measured is introduced from the pipe 81 and the internal pressure of the measurement space 79 increases,
The deformable membrane of the diaphragm 82 is elastically deformed so as to expand outward (downward in FIG. 13). When the deformable film swells outward, the distance between the opposed electrodes 83 and 84 becomes short, and thus the capacitance between the diaphragm 82 and the opposed electrodes 83 and 84 increases. Therefore, as the gas pressure increases, the capacitance increases, and the relationship between the two is linearly proportional in a range where the amount of deformation of the deformable film is small.

Conversely, when the internal pressure of the measurement space 79 decreases, the deformable film of the diaphragm 82 becomes inward (upward in FIG. 13).
It is elastically deformed so as to be recessed. Then, the opposing electrodes 83, 8
4, the capacitance between the diaphragm 82 and the opposing electrodes 83 and 84 decreases.

As described above, since the diaphragm 82 is formed of conductive single-crystal silicon, it functions as a completely elastic body having no hysteresis, brittleness, creep, etc., and measurement accuracy is improved. In addition, high quality mass production is possible by utilizing semiconductor manufacturing technology for silicon wafers.

The room 93 on the opposite side of the diaphragm 82 of the pressure sensor 78 from the measurement space 79 is open to the atmosphere.

In performing the self-diagnosis of the present device,
With the measurement space 79 in communication with the atmosphere, the switch 87
Is operated to make the state of conduction. As a result, the output of the oscillation circuit 41 is given to one counter electrode 83, and the diaphragm 82 moves up and down in FIG. The capacitance detection circuit 26 derives a voltage corresponding to the capacitance between the diaphragm 82 corresponding to the oscillation output of the oscillation circuit 41 and the counter electrodes 83 and 84. As described above, when the measurement space 79 and the space 93 are at the atmospheric pressure, by conducting the switch 87, the capacitance detecting means 26 sets the line 27 on the basis of 0.5 V as shown in FIG. A waveform having a peak value V7 is derived. When the switch 87 is shut off, the line 2
7 is maintained at 0.5V.

When the gas whose gas pressure is to be measured is introduced into the measurement space 79, as shown in FIG. 15 (2), a value obtained by adding the voltage V8 corresponding to the gas pressure to 0.5 V ( = 0.5V + V8) is derived.
By conducting the switch 87 during the self-diagnosis, a pulse 94 corresponding to the oscillation output of the oscillation circuit 41 is obtained.
Diagnosis such as secular change can be performed by the peak value V8 of the pulse 94. Other configurations are the same as those of the above-described embodiment.

[0059]

According to each of the first, second and third aspects of the present invention, an oscillation output and an inverted output obtained by inverting the oscillation output are provided to a pair of counter electrodes provided on both sides of the sensor element in the displacement direction of the pendulum.
Since the voltage is applied through the switching means at the time of diagnosis, the same voltage is not simultaneously applied to the pair of opposed electrodes, and the diagnosis can be reliably performed by a simple operation.

Further, according to the present invention, the oscillation output and the inverted output are given to each of the pair of counter electrodes to cause the pendulum to flex and deform. Therefore, the flexural displacement due to the electrostatic force of the pendulum is as shown in FIG. 14 and FIG. For example, it can be twice as large as that of a certain proposed technique described in connection with the related art, so that the accuracy of the capacitance detecting means at the time of diagnosis can be increased.

According to the present invention, power is supplied from a constant voltage source using a shunt regulator to components such as an oscillation circuit and an inversion circuit for performing diagnosis. Even if there is a variation in the above, a predetermined constant voltage can be supplied to these oscillation circuit and inversion circuit, and the accuracy of diagnosis can be improved. As a result, a diagnostic measurement of a long-term aging of a sensor element or the like can also be accurately performed.

According to the fifth aspect of the present invention, the oscillation frequency is set to about 2 to about 400 Hz, so that it can be accurately diagnosed whether the operation of the sensor element in actual use is normal or not. become.

According to the sixth aspect of the present invention, the oscillating frequency is particularly set to about 2 to about 10 Hz, whereby it is determined whether the detection of the seismic wave at the time of the occurrence of the earthquake is performed normally.
Diagnosis can be made accurately.

According to the seventh aspect of the present invention, the oscillation output waveform is a rectangular wave, and the configuration of the oscillation circuit can be easily realized by, for example, an integrated circuit. , The duty of the square wave is 1
Accordingly, the waveforms applied to the pair of counter electrodes are the same for each half cycle of the rectangular wave, and the acceleration of the sensor element in both the forward and reverse directions can be diagnosed with high accuracy.

According to the eighth aspect of the present invention, the pendulum is made of conductive single-crystal silicon, which can improve the measurement accuracy and realize mass production, and can provide a small, high-quality and low-cost sensor element. .

According to the ninth aspect of the present invention, even a person who does not receive special training for diagnosis can make an accurate diagnosis with a simple operation.

According to the tenth and eleventh aspects of the present invention, a diagnosis in an actual use state can be performed with high accuracy, similarly to the above-described third and fifth aspects of the present invention.

According to the twelfth aspect of the present invention, the diagnosis of the gas pressure sensor can be automatically performed with high accuracy and simple operation.

According to the thirteenth aspect of the present invention, the diaphragm of the gas pressure sensor is made of conductive wire single crystal silicon, thereby improving measurement accuracy and mass production.
In addition, even if it is a gas that enables miniaturization and has corrosiveness such as metal, the gas exists only in the measurement space,
Since it does not come in contact with the counter electrode, the types of gases that can be measured are widened, and applications are expanded. Further, since the counter electrode does not face the measurement space, an explosion-proof structure is possible.

Further, according to the present invention, since the pendulum of the sensor element and the diaphragm of the gas pressure sensor are realized using single crystal silicon, the temperature dependence of the output is reduced regardless of the change in the environmental temperature, and the measurement accuracy is reduced. Can be improved. In addition, this single crystal silicon has an effect that the molecular bonding structure is uniform and cracks are unlikely to occur. Moreover, it is made of silicon, and abundant materials are available.
Further, since the pendulum and the diaphragm can be formed by the etching technique using the manufacturing technique relating to the silicon wafer, the manufacturing is easy, and particularly, the microminiaturization is possible.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an entire configuration of an embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing a specific configuration of constant voltage circuits 38 and 39.

FIG. 3 (1) shows a coupling capacitor 29 of an oscillation circuit 28;
(2) is a waveform diagram showing a voltage waveform applied to the coupling capacitor 30.

FIG. 4 is a waveform chart for explaining the operation of the embodiment shown in FIGS. 1 to 3;

FIG. 5 is a line 27 of the capacitance detecting means 26 shown in FIG.
FIG. 4 is a waveform diagram showing a signal waveform derived from FIG.

FIG. 6 is a diagram illustrating an example of a waveform of an oscillation output led to a line 48 of the oscillation circuit 41.

FIG. 7 is a diagram showing another example of the waveform of the oscillation output led to the line 48 of the oscillation circuit 41.

FIG. 8 is a sectional view of the sensor element 16;

FIG. 9 is a perspective view showing the sensor element 16 with a part cut away.

FIG. 10 is an overall electric circuit diagram of another embodiment of the present invention.

FIG. 11 is an electric circuit diagram showing the entire configuration of another embodiment of the present invention.

FIG. 12 is an electric circuit diagram showing a gas pressure sensor diagnostic device 77 according to another embodiment of the present invention.

FIG. 13 is a cross-sectional view of the gas pressure sensor 78.

14 is a plan view of the gas pressure sensor 78. FIG.

FIG. 15A is a waveform diagram showing an example of a voltage waveform derived from the capacitance detecting means 26 to a line 27, and FIG.
FIG. 7 is a waveform diagram showing another example of a voltage waveform derived from the capacitance detecting means 26 to the line 27.

FIG. 16 is an electric circuit diagram showing the entire configuration of a conventional technique.

17 (1) is a waveform diagram showing an operation state of the switch 12, (2) is a waveform diagram showing an operation state of the switch 13, and (3) is as shown in FIG. 17 (1). FIG. 9 is a waveform diagram showing a pulse waveform obtained on line 6 in a state where switch 12 is turned on and switch 13 is turned off.
(4) is a waveform diagram showing a pulse waveform obtained on the line 6 in a state where the switch 13 is turned on and the switch 12 is turned off as shown in FIG. 17 (2).

[Description of Signs] 16 Sensor element 22 Measurement means 23 Pendulum 24, 25, 83, 84 Counter electrode 26 Capacitance detection circuit 28 Oscillation circuit 29, 30 Coupling capacitor 35 Low pass filter 38, 39 Constant voltage circuit 40 Electric circuit 43, 44, 76 Analog switch 57 Timer 61a Three-terminal regulator 61b Transistor 63 Shunt regulator 77 Gas pressure sensor diagnostic device 78 Gas pressure sensor 79 Measurement space 80 Casing 82 Diaphragm

Continuation of the front page (72) Inventor Masaki Nakasuga 3-4-9 Kikawahigashi, Yodogawa-ku, Osaka-shi, Osaka Inside Sensor Technology Research Laboratories Co., Ltd. (72) Hiroyuki Saito 3-4-2 Kigawahigashi, Yodogawa-ku, Osaka-shi, Osaka No. 9 Inside Sensor Technology Laboratory Co., Ltd. (72) Inventor Tadashi Taniuchi 3-4-9 Kigawa Higashi, Yodogawa-ku Osaka City, Osaka Inside Sensor Technology Laboratory Co., Ltd.

Claims (13)

[Claims] 1. A sensor element, comprising: a conductive pendulum that is cantilevered and elastically bends; and a pair of opposing electrodes that are disposed on both sides in the displacement direction of the pendulum. (B) capacitance detecting means for detecting the capacitance between the pendulum and each counter electrode; (c) an oscillation circuit for deriving an output of a predetermined frequency and applying the output to one counter electrode; (E) supplying an oscillation output and an inverted output to each counter electrode;
A diagnostic device for a capacitance type sensor, comprising: a switching unit for shutting off. 2. A sensor element, comprising: a conductive pendulum that is cantilevered and elastically bends; and a pair of opposing electrodes disposed on both sides in the displacement direction of the pendulum. (B) capacitance detecting means for detecting a capacitance between the pendulum and each counter electrode; (c) an oscillation circuit for deriving an output of a predetermined frequency; and (d) supplying an output of the oscillation circuit. A diagnostic device for a capacitance type sensor, comprising: a switching unit that cuts off and applies the same to one counter electrode; and (e) an inversion unit that inverts the output of the switching unit and applies the same to the other counter electrode. 3. A sensor element comprising: a cantilever-supported and elastically-flexible conductive pendulum; and a pair of opposed electrodes disposed on both sides in the displacement direction of the pendulum. (B) capacitance detecting means for detecting a capacitance between the pendulum and each counter electrode; (c) oscillating means for deriving an output of a predetermined frequency; and (d) output of the oscillating means. A diagnostic device for a capacitive sensor, comprising: a pair of switching elements interposed between the electrodes; and (e) control means for alternately turning on / off the switching means. 4. The diagnostic apparatus according to claim 1, wherein power is supplied to the oscillation circuit and the inversion circuit from a constant voltage source using a shunt regulator. . 5. The oscillation circuit has a frequency of about 2 to about 400H.
The diagnostic device for a capacitive sensor according to claim 1, wherein z is set to z. 6. The oscillation circuit has a frequency of about 2 to about 10 Hz.
5. The method as claimed in claim 1, wherein:
A diagnostic device for a capacitance-type sensor according to any one of the above. 7. The oscillation output of the oscillation circuit is a rectangular wave,
7. The diagnostic device for a capacitive sensor according to claim 5, wherein the duty is 1. 8. The diagnostic apparatus according to claim 1, wherein a pendulum of the sensor element is made of conductive single-crystal silicon. 9. A sensor element, comprising: a conductive pendulum that is cantilevered and elastically bends; and a pair of opposing electrodes disposed on both sides in the displacement direction of the pendulum. A sensor element that provides an oscillation output having a predetermined frequency of the oscillation circuit to one counter electrode, and an inverted signal obtained by inverting the output of the oscillation circuit to the other counter electrode. And diagnosing the sensor element by detecting the capacitance of the sensor. 10. The output of the oscillation circuit is about 2 to about 400H.
10. The method for diagnosing a capacitance-type sensor according to claim 9, wherein z is set to z. 11. The method according to claim 9, wherein the oscillation output of the oscillation circuit is a rectangular wave, and the duty thereof is 1. 12. A gas pressure sensor, comprising: a casing forming a measurement space into which a gas whose gas pressure is to be measured is introduced; and a conductive diaphragm facing the measurement space and elastically deforming according to the gas pressure. A gas pressure sensor having a counter electrode spaced apart in the direction of displacement of the diaphragm; (b) capacitance detecting means for detecting a capacitance between the diaphragm and the counter electrode; and (c) a predetermined frequency. And (d) switching means for supplying / cutting off / on the oscillation output applied between the diaphragm and the counter electrode. Diagnosis device for gas pressure sensor. 13. The gas pressure sensor according to claim 12, wherein the diaphragm is made of conductive single crystal silicon.
A diagnostic device for the gas pressure sensor according to any one of the preceding claims.