JP2000097761A - Piezoelectric sensor circuit and its system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric sensor circuit which can reduce a size, is low-priced, and reduces a consumption power, and further a piezoelectric sensor circuit capable of detecting vibrations without using a circuit which can amplify until a low frequency. SOLUTION: This piezoelectric circuit sensor is provided with three piezoelectric sensors 1 for converting a force generating by vibrations in each direction of three directions to a voltage, an impedance conversion circuit 2 for converting an impedance of the piezoelectric sensor 1, a filter circuit for removing unnecessary frequency components included in an output signal of the piezoelectric sensor 1, FETs 6, 7, 8 for switching signals from the three piezoelectric sensors 1 to one output, and an amplification circuit 4 for amplifying the signal from the piezoelectric sensor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric sensor circuit using a piezoelectric sensor for converting a force such as acceleration or vibration into a voltage by a piezoelectric effect, and a system therefor.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional piezoelectric sensor circuit. This piezoelectric sensor circuit can detect acceleration and vibration in three directions perpendicular to each other. For each direction, a piezoelectric sensor 1, an impedance conversion circuit 2, a filter circuit 3, an amplification circuit 4 using an OP amplifier, and , A reference voltage generating circuit 5. Now, when a force due to acceleration or vibration is generated, the piezoelectric sensor 1
, And the output signal from the piezoelectric sensor 1 is impedance-converted by the impedance conversion circuit 2, unnecessary frequency components in the signal are removed through the filter circuit 3, and the voltage is amplified from the output terminal of the amplification circuit 4. The obtained signal is obtained for each direction. The amplifier circuit 4 is supplied with a reference voltage from the reference voltage generation circuit 5 as an operation reference when a single power supply is driven.

As the impedance conversion circuit 2, FE
A circuit using a source follower circuit of T12 is generally used. The cutoff frequency on the low frequency side of the impedance conversion circuit 2 is determined by the capacitance of the piezoelectric sensor 1 and the resistance connected in parallel to the piezoelectric sensor 1.

As shown in FIG. 9, in order to detect vibrations in three directions of X, Y, and Z, three piezoelectric sensors 1 for X, Y, and Z detection, an impedance conversion circuit 2, a filter circuit 3, And an amplifier circuit 4. When detecting vibration or acceleration having a three-dimensional vector, the direction cosine component of vibration with respect to the surface vector of the detection principal surface of the piezoelectric sensor is detected by the piezoelectric effect, and impedance conversion is performed for each component, and after unnecessary components in the signal are removed. Amplified, X,
Outputs in the Y and Z directions are obtained.

[0005] When detecting vibration due to an earthquake using a piezoelectric sensor, vibration at a low frequency of 0.2 to 0.3 Hz must be detected. Therefore, in detecting low-frequency vibration such as an earthquake, the cutoff frequency determined by the capacitance and resistance of the piezoelectric sensor and the cutoff frequency of the filter circuit 3 as a high-pass filter are set to 0.2 Hz. Since it is difficult to increase the capacity of the high-pass filter circuit due to miniaturization, the resistance of the high-pass filter circuit is increased to obtain a required cutoff frequency. The OP amplifier used in the amplifier circuit 4 also has a high-performance OP that can perform DC amplification.
An amplifier is used.

[0006]

However, in the conventional piezoelectric sensor circuit, in order to make it possible to measure up to a low frequency region, an O which can amplify a high resistance of 10 MΩ or more and a DC component can be used.
A P amplifier is used. Since these components are expensive, there is a problem that the cost of the circuit increases. In addition, there is a problem that the number of components of the circuit increases and the size of the piezoelectric sensor circuit cannot be reduced. In addition, there is a problem that when the device is driven by a power source such as a battery because of high current consumption, the use period is shortened.

The present invention has been made in consideration of the above-described problems, and the vibration can be reduced without using a piezoelectric sensor circuit that can be reduced in size, is inexpensive, and has low power consumption, and a circuit that can amplify to a low frequency. It is an object of the present invention to provide a detectable piezoelectric sensor circuit.

[0008]

According to the first aspect of the present invention, there are provided a plurality of piezoelectric sensors for converting a force in each of a plurality of directions into a voltage, and a plurality of impedances for respectively converting the impedance of the plurality of piezoelectric sensors. The piezoelectric sensor circuit includes a conversion circuit, a switch that outputs one by switching outputs of the plurality of impedance conversion circuits, and an amplification circuit that amplifies an output signal of the switch.

According to a second aspect of the present invention, there are provided a plurality of piezoelectric sensors for converting forces in each of a plurality of directions into voltages, a switch for switching the outputs of the plurality of piezoelectric sensors to one output, and a switch for the output. And an amplifying circuit for amplifying an output signal of the impedance conversion circuit.

In each of the above structures, for example, a switch such as a field effect transistor is used as a switch.
When one of the outputs from one of the piezoelectric sensors passes, the other output is cut off, and only the signal passing through the switch is amplified. As a result, only one amplifying circuit, which is conventionally required for each piezoelectric sensor, is sufficient, and the effects of downsizing, cost reduction, and low power consumption can be obtained.

According to a fourth aspect of the present invention, there is provided the first or second aspect.
Piezoelectric sensor circuit, an A / D converter circuit for converting an output signal of an amplifier circuit of the piezoelectric sensor circuit into a digital signal, and opening / closing control of a switch, and a piezoelectric sensor for each direction from the output signal of the A / D converter circuit. And a control detecting means for detecting the output of the piezoelectric sensor circuit, and an input signal to the amplifier circuit is separated into a pulse signal by opening and closing a switch.

According to a fifth aspect of the present invention, there is provided a piezoelectric sensor circuit according to the third aspect, an A / D conversion circuit for converting an output signal of an amplifier circuit of the piezoelectric sensor circuit into a digital signal, and controlling the opening and closing of a switch. Control detection means for detecting the output of the piezoelectric sensor for each direction from the output signal of the / D conversion circuit,
This is a piezoelectric sensor circuit system in which an input signal to the amplifier circuit is separated into a pulse signal by opening and closing a switch.

In the above configuration, for example, three different voltage waveforms are sequentially switched by a switch to input to an amplifier circuit, combined as a pulse wave, and amplified to obtain three inputs as one output. Thus, when a low-frequency signal is conventionally amplified, the low-frequency cutoff frequency of the gain frequency band is required up to a low-frequency close to DC. Since it is not necessary to widen the range, a general-purpose and inexpensive amplifier can be used.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing an embodiment. (First Embodiment) FIG. 1 is a configuration diagram showing a piezoelectric sensor circuit according to a first embodiment of the present invention. In FIG. 1, 1 is a piezoelectric sensor for detecting a force such as acceleration or vibration, 2 is an impedance conversion circuit for converting the impedance of the piezoelectric sensor 1, and 3 is an unnecessary frequency component contained in a signal from the piezoelectric sensor 1. A filter circuit, which is a high-pass filter to be removed, 4 is an amplifier circuit using an OP amplifier, 5 is a reference voltage generation circuit, and 6, 7, and 8 are switches using a field effect type transistor (hereinafter, referred to as FET). In the present embodiment, in order to detect vibrations in three directions (X, Y, and Z axes) orthogonal to each other,
Filter circuit 3 and amplifying circuit 4
FET acting as a switch provided between the input stage and
By switching among 6, 7, and 8, three inputs are extracted as one output.

If there are a plurality of vibration directions to be detected, for example, only two directions, the vibration 1 in FIG.
The Z-axis piezoelectric sensor 1, the impedance conversion circuit 12, and the filter circuit 3 are unnecessary for the direction detection.
And the switch 8 becomes unnecessary. Conversely, when detecting a plurality of vibrations in n directions, n piezoelectric sensors 1, impedance conversion circuits 12, filter circuits 3, and switches corresponding to the n directions are required.

Next, the operation of the piezoelectric sensor circuit according to the first embodiment will be described with reference to the drawings.

First, when a force due to acceleration or vibration is generated, it is converted into a voltage by the piezoelectric sensor 1 by the piezoelectric effect, and an output signal from the piezoelectric sensor 1 is impedance-converted by the impedance conversion circuit 2 and passes through the filter circuit 3. Unnecessary frequency components in the signal are removed, and an amplified signal is obtained from the output terminal of the amplifier circuit 4. The impedance conversion circuit 2 is a source follower circuit using the FET 12. The amplifying circuit 4 is composed of an OP amplifier, a resistor and a capacitor. The gain G is determined by the ratio R4 / R3 of the resistors R3 and R4. The frequency is determined by 1 / (2πR4C4). Note that the amplifier circuit 4 may be configured using transistors or FETs instead of the OP amplifier (IC).

The FETs 6, 7, 8 as switches are connected in series between the filter circuit 3 and the input terminal of the amplifier circuit 4. The position of the switch is not limited to this configuration because the output signal from the piezoelectric sensor 1 is sufficiently smaller than the reference voltage, and may be provided between the impedance conversion circuit 2 and the filter circuit 3. In that case, the filter circuit can be shared and can be constituted by one.

Gate signal V for opening / closing FETs 6, 7, 8
As x1, Vx2, and Vx3, for example, a pulse wave from a port of the microcomputer is used. When a gate signal is applied to Vx1 and the inputs of the other Vx2 and Vx3 are set to zero, conduction is established between the drain and source of the FET 6, and the output signal from the piezoelectric sensor 1 that has passed through the filter circuit 3 is input to the input stage of the amplifier circuit 4. To be amplified. At this time, the other FETs 7,
Reference numeral 8 denotes a cutoff state, and the output signal from the piezoelectric sensor 1 that has passed through the filter circuit 3 is not input to the amplifier circuit 4.

Next, when a gate signal is applied to the FET 7, conduction is established between the drain and source of the FET 7, and other FETs are connected.
6 and 8 are cut off, and the output of the Y-direction component from the piezoelectric sensor 1 passes through the filter circuit 3 and then passes between the drain and the source of the FET 7 and is amplified in the amplifier circuit 4 to be amplified by the vibration in the other direction. The output of sensor 1 is FET6,8
And is not transmitted to the amplifier circuit 4. Similarly, when a gate signal is applied to the FET 8, an output corresponding to only the vibration component in the Z direction is obtained.

As described above, using the FETs 6, 7, and 8 as switching elements, the outputs from the three piezoelectric sensors 1 are sequentially switched, and the combined signal is transmitted to the amplifier circuit 4 to obtain an amplified output. Among the elements constituting the amplifier circuit 4, the OP amplifier is expensive, and has a larger dimensional size than other elements. In the present invention, since one amplifier circuit 4 is used, the amplification circuit 4 is
Since these parts are unnecessary for two directions, the effects of miniaturization and cost reduction can be expected.

In the power consumption of the piezoelectric sensor circuit,
The power consumption of the amplifier circuit accounts for a large proportion. Since the amplifier used in the amplifier circuit is reduced by two sets,
The power consumption is lower than that of the conventional example shown in FIG. 9, and the power supply such as a battery can be used for a long time. (Second Embodiment) FIG. 2 is a configuration diagram showing a piezoelectric sensor circuit according to a second embodiment of the present invention. In FIG. 2, FETs 6, 7, and 8 as switches are connected to a resistance and an impedance conversion circuit 2 connected in parallel to the piezoelectric sensor 1.
It is connected between the FET 12 inside. Therefore, the filter circuit 3 is connected between the impedance conversion circuit 2 and the amplifier circuit 4. The control of the FETs 6, 7, 8 is performed by the magnitude of the gate-source voltage. In the case of FIG.
Since the source voltages of the FETs 6, 7, and 8 are the same as the gate voltage of the FET 12 in the impedance conversion circuit, it is necessary to set an input gate signal in consideration of the operating point of the FET 12. In this case, the impedance conversion circuits connected to the respective piezoelectric sensors 1 can be shared, and two sets of impedance conversion circuits are not required, and the number of circuit components can be reduced as compared with the case of the above-described first embodiment. Therefore, further miniaturization and cost reduction are expected. In this embodiment, the switching operation is not stable, but a switching FET may be connected between the piezoelectric sensor 1 and the resistor. (Third Embodiment) FIG. 3 is a block diagram showing a piezoelectric sensor circuit system according to a third embodiment of the present invention. In the present embodiment, the first
FIG. 13 is a block diagram of a system for driving a piezoelectric sensor circuit according to a modification of the embodiment and detecting vibration. That is, the system includes three piezoelectric sensors 1,
Three impedance conversion circuits 2 connected to them, a switch 16 for switching three inputs as one output, a filter circuit 3 connected to the switch 16, an amplifier circuit 4 connected to the filter circuit 3, A switch 9 connected to the amplifier circuit 4;
An A / D conversion circuit 10 converts the output signal of the A / D into a digital signal, and a microcomputer 11 as a control detecting means for detecting vibration from the output of the A / D conversion circuit 10. Here, the configuration from the piezoelectric sensor 1 to the amplification circuit 4 is such that the switch 16 is provided between the impedance conversion circuit 2 and the filter circuit 3 in the configuration of FIG. , And is controlled by the microcomputer 11.

Next, the operation of the system of the piezoelectric sensor circuit according to the third embodiment will be described with reference to the drawings.

Now, vibration is applied to the piezoelectric sensors 1, and the force due to the vibration is converted into an electric signal in each piezoelectric sensor 1, and an output waveform as shown in FIG. 6 is obtained from the impedance conversion circuit 2. The frequency of vibration in the X, Y, and Z directions was 0.5 Hz. Next, the output signal of the piezoelectric sensor 1 may or may not be transmitted to the input stage of the amplifier circuit 4 via the filter circuit 3 by the switching of the FET of the switch 16. Switching is performed by gate signals Vx1, Vx2, and V for opening and closing the three FETs.
x3 (see FIG. 1). This gate signal is supplied from the microcomputer 11. As shown in FIG.
The frequencies of the gate signals Vx1, Vx2, Vx3 are equal,
When the phases are shifted from each other by 2π / 3 rad (or 120 degrees), when one FET is in a closed state, another FET is closed.
The two FETs are open. The switching frequency needs to be set higher than the frequency of the signal to be obtained by the sampling theorem. The switching frequency is set to 500 Hz and the duty ratio is set to 0.05. The output waveform from the X, Y, Z direction detecting piezoelectric sensor 1 is as shown in FIG. 7 by the FET 12 as a switch, and transmitted to the input stage of the amplifier circuit 4 via the filter circuit 3. And the amplification circuit 4
The output waveform amplified by the above becomes a composite wave of pulses as shown in FIG. In the case of detecting a vibration or an acceleration having a very low frequency, for example, several Hz, a high-performance amplifier that can amplify a DC component has conventionally been required as the amplifier circuit 4.

In the system of FIG. 3, this composite wave is
By controlling the opening and closing of the switch 9 by the microcomputer 11, the signal is input to the A / D conversion circuit 10 for each direction component. That is, the output waveform of FIG.
Similarly, the frequency is made equal and the phase is set to 2π / 3 rad.
If the switch is opened and closed while being shifted by (or 120 degrees) each time, it is possible to return to the state shown in FIG. 7. After demodulation in this manner, the signal is input to the A / D conversion circuit 10 and X, Y,
Z output waveforms are obtained.

Alternatively, by making the sampling frequency of the A / D conversion circuit 10 coincide with the switching frequency, the magnitudes of the vibrations in the X, Y, and Z directions are sequentially A / D converted and converted into digital values. Can be entered.

The phase difference between the gate signals Vx1, Vx2 and Vx3 of the FET 12 of the switch 16 is 2π / 3 rad.
(Or 120 degrees). When one of FET6,7,8 turns ON, the other two FETs
The switching can be controlled using signals having different phases and frequencies from each other as gate signals so that is turned off. The same applies to the detection of vibrations in a plurality of directions. When detecting the vibration in the n direction, the switching gate signal V
When the frequencies of xi (i; 1 to n) are the same and the phases are shifted from each other by 2π / nrad (or 360 / n degrees), one of the n FETs is turned on, and the other n-1 FETs are turned on.
Is turned off, and the switching can be controlled. Note that the phase difference is not limited to 2π / nrad, and the duty ratio of the gate signal Vx is reduced so that one of the n FETs is sequentially turned on and the other n−1 FETs are turned off. Just do it.

It goes without saying that the circuit having the configuration shown in FIG. 1 may be used as a circuit having a configuration from the piezoelectric sensor 1 to the amplifier circuit 4. (Fourth Embodiment) FIG. 4 is a block diagram showing a system of a piezoelectric sensor circuit according to a fourth embodiment of the present invention. In the present embodiment, the second
FIG. 3 is a block diagram of a system for driving a piezoelectric sensor circuit and detecting vibration according to the embodiment. That is, the system includes three piezoelectric sensors 1 and three piezoelectric sensors 1
, An impedance conversion circuit 2 connected to the switch 16, a filter circuit 3 connected to the impedance conversion circuit 2, an amplification circuit 4 connected to the filter circuit 3, It comprises a switch 9 connected to the circuit 4, an A / D conversion circuit 10 for converting an output signal of the switch 9 into a digital signal, and a microcomputer 11 for detecting vibration from the output of the A / D conversion circuit 10. . Here, the configuration from the piezoelectric sensor 1 to the amplification circuit 4 is the same as the configuration in FIG. 2, and the switch 16 and the switch 9 are controlled by the microcomputer 11.

The operation of the system of the piezoelectric sensor circuit according to the present embodiment is basically the same as that of the above-described third embodiment, and a description thereof will be omitted. In this system, as described in the second embodiment, since only one impedance conversion circuit 2 is required, further reduction in size and cost can be achieved.

As a modification of this embodiment, FIG.
As shown in (2), the configuration may be such that the switch 16 is used only between the piezoelectric sensor 1 and the impedance conversion circuit 2 and the demodulation signal switching element (the switch 9 in FIG. 4) is not used. As described above, it is assumed that vibration occurs, the output of the piezoelectric sensor 1 is switched by the FET of the switch 16, and the signal as shown in FIG. 8 is amplified and A / D converted. The digital signal is read in time series using the microcomputer 11, and the magnitudes of the vibrations in the three directions X, Y, and Z can be determined. In this system, since no switching element is required at the time of demodulation, the number of system components is reduced, and the size and cost can be further reduced as compared with the system of FIG.

The signal shown in FIG. 6 is converted into a pulse wave by the switching element. Assuming that the rising time of the pulse waveform is tr, the frequency of reciprocal frHz of tr is a high-frequency cutoff frequency necessary for observing the wave front. Therefore, the frequency band of the gain required for the amplifier circuit 4 is 10 kHz to
frHz. In each embodiment of the present invention, tr is 1 μm.
sec, and the frequency band of the amplifier circuit 4 is 10 k to 1.
0 MHz. As described above, the cutoff frequency in the conventional low frequency range is a low frequency close to DC, but is shifted to a frequency determined by the pulse width by being split into pulse waves, and the gain required for the amplifier circuit 4 is obtained. The frequency band on the low frequency side becomes narrower toward the high frequency side, and the high-performance OP amplifier capable of amplifying a DC component used in the amplifier circuit 4 can be replaced with an OP amplifier for AC amplification. As a result, the amplifier circuit 4 becomes inexpensive, which leads to a reduction in the cost of the piezoelectric sensor circuit.

As described above, according to the present invention, a vibration having a three-dimensional vector is made one output by using a pulse method by switching and a modulation method by combining three waveforms. Then, by performing demodulation, the vibration of each of the three-dimensional directional components is detected. The number of amplifier circuits is reduced to one third as compared with the conventional case, and the number of components used is reduced. Further, since the low-frequency signal is split into pulse waves, the frequency band of the gain of the amplifier circuit may be a frequency band capable of amplifying the pulse wave, and a highly versatile AC amplifier circuit can be used. The effects of miniaturization, cost reduction, and low power consumption can be obtained as compared with the related art.

In each of the above embodiments, an example of a configuration using three piezoelectric sensors has been described. However, the present invention is not limited to this.
The present invention can be applied to a case where two or four or more piezoelectric sensors are used in accordance with the number of vibration directions to be detected.

In the above embodiment, the microcomputer is used as the control detecting means. Alternatively, the control detecting means may be constituted by dedicated hardware having the same function.

[0035]

As is apparent from the above description, the present invention provides a plurality of piezoelectric sensors for converting forces in each of a plurality of directions into voltages, and a plurality of piezoelectric sensors for respectively converting the impedances of the plurality of piezoelectric sensors. Since there are provided an impedance conversion circuit, a switch for switching the outputs of the plurality of impedance conversion circuits to one output, and an amplifier circuit for amplifying an output signal of the switch, miniaturization, cost reduction, and low power consumption are provided. It has the advantage that it can be used.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a piezoelectric sensor circuit according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a piezoelectric sensor circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a piezoelectric sensor circuit system according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a piezoelectric sensor circuit system according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a modification of the fourth embodiment.

FIG. 6 is a diagram illustrating an example of a piezoelectric sensor output in each of three directions.

FIG. 7 is a diagram showing a voltage waveform before an amplifier circuit input stage at the time of sensor output of FIG. 6;

8 is a diagram showing an output waveform of an amplifier circuit when the sensor of FIG. 6 is output.

FIG. 9 is a configuration diagram of a conventional piezoelectric sensor circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 piezoelectric sensor 2 impedance conversion circuit 3 filter circuit 4 amplification circuit 5 reference voltage generation circuit 6, 7, 8, 12 FET (field effect transistor) 9, 16 switch (SW) 10 A / D conversion circuit 11 microcomputer

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoshihiro Tomita 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In-house F-term (reference) 2G064 AA11 AB02 BA02 BA03 BD18 CC02 CC13 CC22 CC46

Claims (8)

[Claims] 1. A plurality of piezoelectric sensors for respectively converting forces in each of a plurality of directions into a voltage, a plurality of impedance conversion circuits for respectively converting the impedances of the plurality of piezoelectric sensors, and outputs of the plurality of impedance conversion circuits. A piezoelectric sensor circuit, comprising: a switch that outputs one output by switching the switch; and an amplifier circuit that amplifies an output signal of the switch. 2. A plurality of piezoelectric sensors for converting a force in each of a plurality of directions into a voltage, a switch for switching the output of the plurality of piezoelectric sensors to one output, and the piezoelectric connected by the switch. An impedance conversion circuit for converting the impedance of the sensor;
A piezoelectric sensor circuit comprising: an amplifier circuit for amplifying an output signal of the impedance conversion circuit. 3. The piezoelectric sensor circuit according to claim 1, wherein the plurality of directions are three directions orthogonal to each other. 4. The piezoelectric sensor circuit according to claim 1 or 2, an A / D conversion circuit for converting an output signal of the amplification circuit of the piezoelectric sensor circuit into a digital signal, and opening and closing control of the switch, Control detection means for detecting the output of the piezoelectric sensor in each of the directions from the output signal of the A / D conversion circuit, wherein the input signal to the amplification circuit is separated into a pulse signal by opening and closing the switch. Characteristic piezoelectric sensor circuit system. 5. The piezoelectric sensor circuit according to claim 3, an A / D conversion circuit for converting an output signal of the amplification circuit of the piezoelectric sensor circuit into a digital signal, and controlling the opening and closing of the switch, thereby controlling the A / D conversion. Control detection means for detecting the output of the piezoelectric sensor for each direction from the output signal of the conversion circuit, and the input signal to the amplification circuit is separated into a pulse signal by opening and closing the switch. Piezoelectric sensor circuit system 6. A case where the plurality of directions are three directions, and a switching signal having a frequency higher than the frequency of the output signal and a phase different from each other by 120 degrees is provided for each output signal from each of the piezoelectric sensors. The piezoelectric sensor circuit system according to claim 5, wherein after opening and closing the switch to separate each signal into pulse waves, the three pulse waves are sequentially combined and input to the amplifier circuit. . 7. An amplifier according to claim 1, further comprising another switch for opening and closing the output of said amplifier circuit, and opening and closing said another switch to output an output corresponding to each of said three directions to said A / A.
The piezoelectric sensor circuit system according to claim 5, wherein after conversion by the D converter, detection is performed by the control detection unit. 8. The circuit according to claim 1, wherein the A
7. The piezoelectric device according to claim 5, wherein an output corresponding to each of the three directions is detected by the control detection unit by associating sampling of a / D converter with opening and closing of the switch. 8. Sensor circuit system.