Capacitive Sensor

Abstract

To materialize a digital input compatible with both a dual power source and a single power source.SOLUTION: A capacitive sensor 1 comprises: a sensor unit 100 having capacitance changed according to physical quantity of a measurement object; a microprocessor 106 converting the capacitance into a measurement value of the physical quantity; and a digital input circuit 108 which is provided between a digital input terminal DI and an input port PI of the microprocessor 106 and is used for setting functions of the microprocessor 106. The digital input circuit 108 converts the level of voltage at the digital input terminal DI into the level of voltage at the input port PI of the microprocessor 106.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a capacitance type sensor used as a pressure sensor or the like. [Background technology]

[0002] Conventionally, capacitance sensors in which the capacitance varies according to a physical quantity have been used as pressure sensors, for example (see Patent Document 1). The circuit of a capacitance sensor is shown in Fig. 9. In a capacitance sensor, a sine wave is applied from a signal generator 101 to a sensor unit 100 whose capacitance CX varies according to the physical quantity (e.g., pressure) to be measured. A charge amplifier circuit 102 consisting of a capacitance CF and an operational amplifier A1 converts the current output from the sensor unit 100 into a voltage and amplifies it.

[0003] The detection circuit 103 full-wave rectifies the signal amplified by the charge amplifier circuit 102. A low-pass filter (LPF) 104 smoothes the output of the detection circuit 103. In this way, a capacitance signal based on the capacitance CX is obtained. This capacitance signal is converted into a digital signal by an AD converter 105 (for example, a ΔΣ type AD converter). A microprocessor 106 converts the digital signal into a pressure measurement value.

[0004] The pressure sensor has a digital input terminal, and the user can freely change the product settings by shorting the digital input terminal to ground potential. For example, when performing pressure zero point adjustment (adjusting the sensor output value to zero at zero pressure), adjustment can be made by shorting a specific digital input terminal to ground.

[0005] On the other hand, some pressure sensors are compatible with multiple power supply configurations, and one product can be used with either dual power supplies of ±15V or a single power supply of +24V simply by changing the wiring. In such power supply configurations, whether the user uses dual power supplies or a single power supply, the voltage value when the digital input is enabled and the voltage value when the digital input is disabled must be the same for each power supply configuration. However, conventional pressure sensors had an issue where the voltage value of the digital input would change depending on the power supply configuration, even if the product was compatible with multiple power supply configurations.

[0006] In recent years, pressure sensors (diaphragm vacuum gauges) mainly used in semiconductor manufacturing processes have become necessary to heat the sensor part of the pressure sensor to match the temperature inside the equipment as the temperature inside the equipment changes depending on the process, such as the semiconductor film formation process and cleaning process. In addition, it is possible to accurately measure pressure by performing zero point adjustment for the output of the pressure sensor after each process. Setting changes in pressure sensors are often performed manually by workers one by one, but if digital input to the pressure sensor can be made from a central control system, for example, setting changes can be made efficiently. In order to accommodate such setting changes from a central location, it is desirable for the digital input of the pressure sensor to support both dual and single power supplies. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2005-331328 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made to solve the above-mentioned problems, and has an object to provide a digital input that is compatible with both dual power supplies and single power supplies in a capacitance type sensor. [Means for solving the problem]

[0009] The capacitance type sensor of the present invention includes a sensor unit configured to change capacitance in response to a physical quantity of a measurement target, a processor configured to convert the capacitance into a measurement value of the physical quantity, and a digital input circuit for setting functions of the processor, the digital input circuit being provided between a digital input terminal of the capacitance type sensor and an input port of the processor, the digital input circuit including a level shift circuit for converting a high / low voltage of the digital input terminal into a high / low voltage of the input port of the processor. the input / output terminal of the PNP transistor is connected to a user power supply voltage at its emitter terminal; an NPN transistor having a collector terminal connected to an output terminal of a digital input circuit and an emitter terminal connected to ground; a first resistor having one end connected to the emitter terminal of the PNP transistor and the other end connected to a base terminal of the PNP transistor; a second resistor having one end connected to the digital input terminal and the other end connected to the base terminal of the PNP transistor; a third resistor having one end connected to the collector terminal of the PNP transistor and the other end connected to the base terminal of the NPN transistor; a fourth resistor having one end supplied with the power supply voltage for the processor and the other end connected to the collector terminal of the NPN transistor; and a fifth resistor having one end connected to the base terminal of the NPN transistor and the other end connected to the emitter terminal of the NPN transistor. It is characterized by the above.

[0011] The capacitance type sensor of the present invention a sensor unit configured to change capacitance in response to a physical quantity of a measurement target, a processor configured to convert the capacitance into a measurement value of the physical quantity, and a digital input circuit for setting functions of the processor, the digital input circuit being provided between a digital input terminal of the capacitance type sensor and an input port of the processor, the digital input circuit including a level shift circuit for converting a high / low voltage of the digital input terminal into a high / low voltage of the input port of the processor, The user power supply voltage is supplied to the source terminal. RuP A type MOSFET with its drain terminal connected to the output terminal of the digital input circuit and its source terminal connected to ground. N a first resistor having one end connected to the digital input terminal and the other end connected to the gate terminal of the P-type MOSFET; a second resistor having one end connected to the digital input terminal and the other end connected to the gate terminal of the P-type MOSFET; a third resistor having one end connected to the drain terminal of the P-type MOSFET and the other end connected to the gate terminal of the N-type MOSFET; a fourth resistor having one end supplied with a power supply voltage for the processor and the other end connected to the drain terminal of the N-type MOSFET; and a fifth resistor having one end connected to the gate terminal of the N-type MOSFET and the other end connected to the source terminal of the N-type MOSFET.

[0012] The capacitance type sensor of the present invention a sensor unit configured to change capacitance in response to a physical quantity of a measurement target, a processor configured to convert the capacitance into a measurement value of the physical quantity, and a digital input circuit for setting functions of the processor, the digital input circuit being provided between a digital input terminal of the capacitance type sensor and an input port of the processor, the digital input circuit including a level shift circuit for converting a high / low voltage of the digital input terminal into a high / low voltage of the input port of the processor, The user power supply voltage is supplied to the emitter terminal. RuP An NP type transistor with its drain terminal connected to the output terminal of the digital input circuit and its source terminal connected to ground. Na first resistor having one end connected to the emitter terminal of the PNP transistor and the other end connected to the base terminal of the PNP transistor, a second resistor having one end connected to the digital input terminal and the other end connected to the base terminal of the PNP transistor, a third resistor having one end connected to the collector terminal of the PNP transistor and the other end connected to the gate terminal of the N-type MOSFET, a fourth resistor having one end supplied with a power supply voltage for the processor and the other end connected to the drain terminal of the N-type MOSFET, and a fifth resistor having one end connected to the gate terminal of the N-type MOSFET and the other end connected to the source terminal of the N-type MOSFET.

[0013] The capacitance type sensor of the present invention a sensor unit configured to change capacitance in response to a physical quantity of a measurement target, a processor configured to convert the capacitance into a measurement value of the physical quantity, and a digital input circuit for setting functions of the processor, the digital input circuit being provided between a digital input terminal of the capacitance type sensor and an input port of the processor, the digital input circuit including a level shift circuit for converting a high / low voltage of the digital input terminal into a high / low voltage of the input port of the processor, The user power supply voltage is supplied to the source terminal. RuP The collector terminal is connected to the output terminal of the digital input circuit, and the emitter terminal is connected to ground. N a PN transistor, a first resistor having one end connected to the source terminal of the P-type MOSFET and the other end connected to the gate terminal of the P-type MOSFET, a second resistor having one end connected to the digital input terminal and the other end connected to the gate terminal of the P-type MOSFET, a third resistor having one end connected to the drain terminal of the P-type MOSFET and the other end connected to the base terminal of the NPN transistor, a fourth resistor having one end supplied with a power supply voltage for the processor and the other end connected to the collector terminal of the NPN transistor, and a fifth resistor having one end connected to the base terminal of the NPN transistor and the other end connected to the emitter terminal of the NPN transistor. In addition, the capacitance type sensor of the present invention comprises a sensor unit configured to change the capacitance depending on the pressure of the object to be measured, a processor configured to convert the capacitance into a pressure measurement value, and a digital input circuit for setting the functions of the processor, which is provided between a digital input terminal of the capacitance type sensor and an input port of the processor, the digital input circuit including a level shift circuit that converts the high and low voltage of the digital input terminal into the high and low voltage of the input port of the processor, and the processor adjusts the pressure measurement value depending on the output of the level shift circuit which corresponds to the voltage of the digital input terminal, and stores a pressure correction value as a result of the adjustment. In addition, in one configuration example of the capacitance type sensor of the present invention, the processor is characterized in that when the output of the level shift circuit becomes a voltage indicating a valid output, it automatically performs zero point adjustment and stores a pressure correction value of the adjustment result. Effect of the Invention

[0014] According to the present invention, by providing a digital input circuit including a level shift circuit that converts the high and low voltages of the digital input terminal into the high and low voltages of the input port of the processor, the voltage input to the processor becomes the same regardless of whether the power supply connected to the capacitive sensor is a dual power supply or a single power supply. Therefore, the digital input of the present invention can be used with either a dual power supply or a single power supply. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a block diagram showing the configuration of a capacitance type sensor according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a circuit diagram showing a configuration of a digital input circuit according to a first embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram for explaining the operation of the digital input circuit when both power sources are connected to the capacitance type sensor in the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing a case where a single power supply is connected to the capacitance type sensor in the first embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram for explaining the operation of the digital input circuit when a single power supply is connected to the capacitance type sensor in the first embodiment of the present invention. [Figure 6] FIG. 6 is a circuit diagram showing a configuration of a digital input circuit according to a second embodiment of the present invention. [Figure 7] FIG. 7 is a circuit diagram showing another configuration of the digital input circuit according to the second embodiment of the present invention. [Figure 8] FIG. 8 is a circuit diagram showing another configuration of the digital input circuit according to the second embodiment of the present invention. [Figure 9] FIG. 9 is a block diagram showing a circuit configuration of the capacitance type sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] [First Example] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a capacitance type sensor 1 according to a first embodiment of the present invention, and the same components as those in Fig. 9 are given the same reference numerals. In Fig. 1, the charge amplifier circuit 102, the detection circuit 103, the low-pass filter 104, and the AD converter 105 in Fig. 9 are shown as a circuit section 107.

[0017] As described above, the capacitance signal converted into a digital signal by the AD converter of the circuit section 107 is converted into a pressure measurement value by the microprocessor 106. The microprocessor 106 executes processing according to a program stored in an internal memory (not shown).

[0018] The digital input circuit 108 is provided for setting the functions of the capacitance type sensor 1, and has an input terminal connected to the digital input terminal DI of the capacitance type sensor 1 and an output terminal connected to the input port PI of the microprocessor 106. The power supply circuit 109 converts the voltage supplied from a power supply 200 connected to the capacitance type sensor 1 into a power supply voltage VCC=3.3 V for the processor.

[0019] 2 is a circuit diagram showing the configuration of the digital input circuit 108 of this embodiment. The digital input circuit is composed of a PNP transistor Q1, the emitter terminal of which is supplied with a user power supply voltage VU (=VI), an NPN transistor Q2, the collector terminal of which is connected to the output terminal of the digital input circuit 108 (the input port PI of the microprocessor 106) and the emitter terminal of which is connected to the system ground GND, a resistor R1, one end of which is connected to the emitter terminal of the transistor Q1 and the other end of which is connected to the base terminal of the transistor Q1, a resistor R2, one end of which is connected to the digital input terminal DI and the other end of which is connected to the base terminal of the transistor Q1, a resistor R3, one end of which is connected to the collector terminal of the transistor Q1 and the other end of which is connected to the base terminal of the transistor Q2, a resistor R4, one end of which is supplied with a power supply voltage VCC and the other end of which is connected to the collector terminal of the transistor Q2, and a resistor R5, one end of which is connected to the base terminal of the transistor Q2 and the other end of which is connected to the emitter terminal of the transistor Q2.

[0020] Fig. 3 is a diagram for explaining the operation of the digital input circuit when both power supplies of ±15 V are connected as the power supply 200 to the positive power supply terminal VI, the COM terminal, and the negative power supply terminal VM of the capacitance type sensor 1 as shown in Fig. 1. In Fig. 3, DIs is the voltage of the digital input terminal DI in a short-circuited state, DIo is the voltage of the digital input terminal DI in an open state, CTs is the voltage of the collector terminal of the transistor Q1 when the digital input terminal DI is short-circuited, CTo is the voltage of the collector terminal of the transistor Q1 when the digital input terminal DI is open, PIs is the voltage of the output terminal of the digital input circuit 108 when the digital input terminal DI is short-circuited, and PIo is the voltage of the output terminal of the digital input circuit 108 when the digital input terminal DI is open.

[0021] When the user shorts the digital input terminal DI and the COM terminal, the transistor Q1 turns on and a voltage of CTs=30V is applied to the resistor R3. This turns on the transistor Q2 and the voltage of the output terminal of the digital input circuit 108 becomes PIs=0V. On the other hand, when the user opens the digital input terminal DI, the transistor Q1 turns off. Since the voltage of the collector terminal of the transistor Q1 becomes CTo=0V, the transistor Q2 also turns off and the voltage of the output terminal of the digital input circuit 108 becomes PIo=3.3V.

[0022] Fig. 5 is a diagram for explaining the operation of the digital input circuit when a single power supply of +24 V is connected as the power supply 200 to the positive power supply terminal VI, the COM terminal, and the negative power supply terminal VM of the capacitance sensor 1 as shown in Fig. 4. In the case of a single power supply, the COM terminal and the negative power supply terminal VM are shorted for use.

[0023] When a single power supply of +24V is connected as the power supply 200, if the user shorts the digital input terminal DI and the COM terminal, the transistor Q1 turns on and a voltage of CTs=24V is applied to the resistor R3. This turns on the transistor Q2 and the voltage of the output terminal of the digital input circuit 108 becomes PIs=0V. On the other hand, if the user opens the digital input terminal DI, the transistor Q1 turns off. Since the voltage of the collector terminal of the transistor Q1 becomes CTo=0V, the transistor Q2 also turns off and the voltage of the output terminal of the digital input circuit 108 becomes PIo=3.3V.

[0024] As described above, in this embodiment, by providing a digital input circuit 108 (level shift circuit) including two-stage transistors Q1 and Q2, the voltage input to the microprocessor 106 becomes the same voltage whether the power supply 200 connected to the capacitance sensor 1 is a dual power supply or a single power supply (PIs=0V when the digital input terminal DI is short-circuited, and PIo=3.3V when the digital input terminal DI is open). Therefore, the digital input of this embodiment can be used with either a dual power supply or a single power supply.

[0025] The microprocessor 106 provides a predefined function according to the state of the input port PI. For example, taking the pressure zero point adjustment function as an example, when the digital input becomes valid (PIs=0V), the microprocessor 106 automatically performs zero point adjustment so that the pressure measurement value becomes 0, and stores the pressure correction value resulting from the adjustment.

[0026] [Second Example] In the first embodiment, bipolar transistors are used in the digital input circuit 108, but MOSFETs may also be used. The configuration of the digital input circuit 108 when MOSFETs are used is shown in Fig. 6. In this embodiment, the PNP transistor Q1 of the first embodiment is replaced with a P-type MOSFET Q3, and the NPN transistor Q2 is replaced with an N-type MOSFET Q4.

[0027] A P-type MOSFET Q3 has a gate terminal connected to resistors R1 and R2, a source terminal to which the user power supply voltage VU is supplied, and a drain terminal connected to a resistor R3. An N-type MOSFET Q4 has a gate terminal connected to resistors R3 and R5, a drain terminal connected to the output terminal of a digital input circuit 108, and a source terminal connected to the system ground GND.

[0028] That is, the base terminal of the transistor Q1 in the first embodiment may be replaced with the gate terminal of a P-type MOSFET Q3, the collector terminal of the transistor Q1 with the drain terminal of the P-type MOSFET Q3, and the emitter terminal of the transistor Q1 with the source terminal of the P-type MOSFET Q3. Similarly, the base terminal of the transistor Q2 may be replaced with the gate terminal of an N-type MOSFET Q4, the collector terminal of the transistor Q2 with the drain terminal of the N-type MOSFET Q4, and the emitter terminal of the transistor Q2 with the source terminal of the N-type MOSFET Q4.

[0029] The on / off operation of the FETs Q3 and Q4 is the same as that of the transistors Q1 and Q2, and therefore a description thereof will be omitted.

[0030] Also, as shown in FIG. 7, the NPN transistor Q2 in the first embodiment may be replaced with an N-type MOSFET Q4. As shown in FIG. 8, the PNP transistor Q1 of the first embodiment may be replaced with a P-type MOSFET Q3. [Industrial Applicability]

[0031] The present invention can be applied to a capacitance type sensor such as a pressure sensor. [Explanation of symbols]

[0032] 1...capacitive sensor, 100...sensor section, 101...signal generator, 102...charge amplifier circuit, 103...detection circuit, 104...low-pass filter, 105...AD converter, 106...microprocessor, 107...circuit section, 108...digital input circuit, 109...power supply circuit, 200...power supply, Q1...PNP transistor, Q2...NPN transistor, Q3...P-type MOSFET, Q4...N-type MOSFET, R1 to R4...resistors.

Claims

1. A sensor unit configured such that a capacitance changes in response to a physical quantity of a measurement target; a processor configured to convert the capacitance into a measure of the physical quantity; a digital input circuit for setting functions of the processor, the digital input circuit being provided between a digital input terminal of the capacitance type sensor and an input port of the processor; the digital input circuit includes a level shift circuit that converts a high or low voltage of the digital input terminal into a high or low voltage of an input port of the processor; A PNP transistor having an emitter terminal to which a user power supply voltage is supplied; an NPN transistor having a collector terminal connected to an output terminal of the digital input circuit and an emitter terminal connected to ground; a first resistor having one end connected to the emitter terminal of the PNP transistor and the other end connected to the base terminal of the PNP transistor; a second resistor having one end connected to the digital input terminal and the other end connected to the base terminal of the PNP transistor; a third resistor having one end connected to the collector terminal of the PNP transistor and the other end connected to the base terminal of the NPN transistor; a fourth resistor having one end to which a power supply voltage for the processor is supplied and the other end connected to the collector terminal of the NPN transistor; a fifth resistor having one end connected to the base terminal of the NPN transistor and the other end connected to the emitter terminal of the NPN transistor.

2. A sensor unit configured such that its capacitance changes in response to a physical quantity of a measurement target; a processor configured to convert the capacitance into a measure of the physical quantity; a digital input circuit for setting functions of the processor, the digital input circuit being provided between a digital input terminal of the capacitance type sensor and an input port of the processor; the digital input circuit includes a level shift circuit that converts a high or low voltage of the digital input terminal into a high or low voltage of an input port of the processor; A P-type MOSFET having a source terminal supplied with a user power supply voltage; an N-type MOSFET having a drain terminal connected to an output terminal of the digital input circuit and a source terminal connected to ground; a first resistor having one end connected to a source terminal of the P-type MOSFET and the other end connected to a gate terminal of the P-type MOSFET; a second resistor having one end connected to the digital input terminal and the other end connected to the gate terminal of the P-type MOSFET; a third resistor having one end connected to the drain terminal of the P-type MOSFET and the other end connected to the gate terminal of the N-type MOSFET; a fourth resistor having one end to which a power supply voltage for the processor is supplied and the other end connected to the drain terminal of the N-type MOSFET; and a fifth resistor having one end connected to the gate terminal of the N-type MOSFET and the other end connected to the source terminal of the N-type MOSFET.

3. A sensor unit configured such that its capacitance changes in response to a physical quantity of a measurement target; a processor configured to convert the capacitance into a measure of the physical quantity; a digital input circuit for setting functions of the processor, the digital input circuit being provided between a digital input terminal of the capacitance type sensor and an input port of the processor; the digital input circuit includes a level shift circuit that converts a high or low voltage of the digital input terminal into a high or low voltage of an input port of the processor; A PNP transistor having an emitter terminal to which a user power supply voltage is supplied; an N-type MOSFET having a drain terminal connected to an output terminal of the digital input circuit and a source terminal connected to ground; a first resistor having one end connected to the emitter terminal of the PNP transistor and the other end connected to the base terminal of the PNP transistor; a second resistor having one end connected to the digital input terminal and the other end connected to the base terminal of the PNP transistor; a third resistor having one end connected to the collector terminal of the PNP transistor and the other end connected to the gate terminal of the N-type MOSFET; a fourth resistor having one end to which a power supply voltage for the processor is supplied and the other end connected to the drain terminal of the N-type MOSFET; and a fifth resistor having one end connected to the gate terminal of the N-type MOSFET and the other end connected to the source terminal of the N-type MOSFET.

4. A sensor unit configured such that its capacitance changes in response to a physical quantity of a measurement target; a processor configured to convert the capacitance into a measure of the physical quantity; a digital input circuit for setting functions of the processor, the digital input circuit being provided between a digital input terminal of the capacitance type sensor and an input port of the processor; the digital input circuit includes a level shift circuit that converts a high or low voltage of the digital input terminal into a high or low voltage of an input port of the processor; A P-type MOSFET having a source terminal supplied with a user power supply voltage; an NPN transistor having a collector terminal connected to an output terminal of the digital input circuit and an emitter terminal connected to ground; a first resistor having one end connected to a source terminal of the P-type MOSFET and the other end connected to a gate terminal of the P-type MOSFET; a second resistor having one end connected to the digital input terminal and the other end connected to the gate terminal of the P-type MOSFET; a third resistor having one end connected to the drain terminal of the P-type MOSFET and the other end connected to the base terminal of the NPN transistor; a fourth resistor having one end to which a power supply voltage for the processor is supplied and the other end connected to the collector terminal of the NPN transistor; a fifth resistor having one end connected to the base terminal of the NPN transistor and the other end connected to the emitter terminal of the NPN transistor.

5. A sensor unit configured such that its capacitance changes in response to the pressure of the object to be measured; a processor configured to convert the capacitance into a pressure measurement; a digital input circuit for setting functions of the processor, the digital input circuit being provided between a digital input terminal of the capacitance type sensor and an input port of the processor; the digital input circuit includes a level shift circuit that converts a high or low voltage of the digital input terminal into a high or low voltage of an input port of the processor; The processor adjusts the pressure measurement value according to an output of the level shift circuit corresponding to the voltage of the digital input terminal, and stores a pressure correction value as a result of the adjustment. A capacitance type sensor characterized by:

6. The capacitance type sensor according to claim 5, The processor automatically performs zero point adjustment when the output of the level shift circuit becomes a valid voltage, and stores a pressure correction value of the adjustment result. A capacitance type sensor characterized by:

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