JP2013134078A - Capacitive physical quantity detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitive physical quantity detection apparatus capable of performing self-diagnosis even without including a movable electrode like a humidity sensor, etc.SOLUTION: A capacitive physical quantity detection apparatus comprises a sensor unit 10, first control means 50, self-diagnosis signal application means 40, and detection means 60. The sensor unit 10 includes first and second fixed electrodes 12a and 12b and a common electrode 11 facing the first and second fixed electrodes 12a and 12b. The first control means 50 applies a predetermined potential to the first and second fixed electrodes 12a and 12b and outputs a predetermined control signal during self-diagnosis. The self-diagnosis signal application means 40 brings the common electrode 11 into a predetermined state on the basis of the control signal from the first control means 50 during self-diagnosis. The detection means 60 detects a current flowing to the sensor unit 10 during self-diagnosis. Thus, abnormality in the sensor unit 10 is detected by detecting a current flowing to the sensor unit 10, so that self-diagnosis can be performed even in a capacitive physical quantity detection apparatus which does not include a movable electrode.

Description

  The present invention relates to a capacitive physical quantity detection device that detects a physical quantity in accordance with a capacitance, and is preferably applied to, for example, a humidity sensor that detects humidity.

  Conventionally, for example, Patent Document 1 has proposed a capacitive physical quantity detection device capable of performing self-diagnosis. Specifically, such a capacitive physical quantity detection device includes a sensor unit having first and second fixed electrodes and a movable common electrode facing these fixed electrodes.

  Then, at the time of self-diagnosis, first, a predetermined voltage is applied between the common electrode and the first and second fixed electrodes to generate an electrostatic attractive force so that the common electrode is brought into contact with one fixed electrode. That is, the common electrode is stuck to the fixed electrode. After that, the self-diagnosis is performed to determine whether or not there is an abnormality in the sensor unit by returning to the normal state and detecting whether or not the common electrode is separated from the fixed electrode.

JP 2005-43309 A

  However, although the above-described capacitive physical quantity detection device can perform self-diagnosis by intentionally generating sticking, it is difficult to apply to a device such as a humidity sensor where the common electrode is a fixed electrode. There is a problem that.

  In view of the above points, an object of the present invention is to provide a capacitive physical quantity detection device that can perform self-diagnosis even in a device that does not have a movable electrode such as a humidity sensor.

  In order to achieve the above object, according to the first aspect of the present invention, the semiconductor substrate (13) is used, and the first and second fixed electrodes (12a, 12b) and the first and second fixed electrodes (12a, 12b) and a sensor unit (10) having a common electrode (11) opposite to the first and second fixed electrodes (12a, 12b) at the time of self-diagnosis, and a predetermined control signal is output. 1 control means (50), self-diagnosis signal applying means (40) for setting the common electrode (11) in a predetermined state based on a control signal from the first control means (50) during self-diagnosis, and a sensor during self-diagnosis Detecting means (60) for detecting the current flowing through the section (10), and applying a predetermined potential from the first control means (50) to the first and second fixed electrodes (12a, 12b) during self-diagnosis The common electrode (11) Self-diagnostic means (40 to 60) for detecting an abnormality of the sensor section (10) by making the diagnosis signal applying means (40) a predetermined state and detecting the current flowing through the sensor section (10) by the detection means (60). ).

  According to this, by applying a predetermined potential to the first and second fixed electrodes (12a, 12b), setting the common electrode (11) in a predetermined state, and detecting the current flowing through the sensor unit (10), the sensor Since the abnormality of the part (10) is detected, the self-diagnosis can be performed even in the capacitive physical quantity detection device having no movable electrode.

  In this case, as in the invention described in claim 2, the self-diagnosis means (40-60) is connected to the first control means (50) at the first and second fixed electrodes (12a, 12b) during the self-diagnosis. A high level potential higher than the ground potential is applied to the common electrode (11) to be in a floating state by the self-diagnosis signal applying means (40).

  According to this, it is possible to detect whether the first and second fixed electrodes (12a, 12b) are short-circuited with the semiconductor substrate (13).

  Further, as in the invention described in claim 3, the self-diagnosis means (40-60) is connected to the first and second fixed electrodes (12a, 12b) from the first control means (50) during the self-diagnosis. Self-diagnosis signal applying means when a high level or ground potential higher than the ground potential is applied and a high level potential is applied to the common electrode (11) and the first and second fixed electrodes (12a, 12b). When a ground potential is applied by (40) and a ground potential is applied to the first and second fixed electrodes (12a, 12b), a high level potential higher than the ground potential by the self-diagnosis signal applying means (40). Can be applied.

  According to this, it is determined whether the common electrode (11) and the first fixed electrode (12a) are short-circuited, or whether the common electrode (11) and the second fixed electrode (12b) are short-circuited. Can be detected.

  Further, as in the invention described in claim 4, the self-diagnosis means (40-60) is connected to the first and second fixed electrodes (12a, 12b) from the first control means (50) during the self-diagnosis. Self-diagnosis signal applying means when a high level or ground potential higher than the ground potential is applied and a high level potential is applied to the common electrode (11) and the first and second fixed electrodes (12a, 12b). When a high level potential higher than the ground potential is applied by (40) and the ground potential is applied to the first and second fixed electrodes (12a, 12b), the self-diagnostic signal applying means (40) Can be applied.

  According to this, it is possible to detect whether or not the common electrode (11) is short-circuited with the semiconductor substrate (13).

  Further, as in the invention described in claim 5, the self-diagnosis means (40-60) is connected to the first and second fixed electrodes (12a, 12b) from the first control means (50) during the self-diagnosis. A high level potential higher than the ground potential can be applied to one of them and a ground potential can be applied to the other, and the common electrode (11) can be brought into a floating state by the self-diagnosis signal applying means (40).

  According to this, it is possible to detect whether or not the first fixed electrode (12a) and the second fixed electrode (12b) are short-circuited.

  Further, as in the sixth aspect of the invention, the signal processing means (30) connected to the sensor section (10) to process the signal from the sensor section (10), and the signal processing means ( And a second control means (50) for stopping the operation of 30).

  And like invention of Claim 7, a sensor part (10) shall detect humidity. Further, as in the invention described in claim 8, the sensor unit (10) can detect a material having dielectric characteristics.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a block diagram of the humidity sensor in a 1st embodiment of the present invention. (A) is a top view of a sensor part, (b) is AA sectional drawing of (a). It is a timing chart at the time of the action | operation of the humidity sensor shown in FIG. It is a top view of the sensor part in other embodiments. (A) is BB sectional drawing in FIG. 4, (b) is CC sectional drawing in FIG. It is a top view of the sensor part in other embodiments. (A) is DD sectional drawing in FIG. 6, (b) is EE sectional drawing in FIG. It is a top view of the sensor part in other embodiments. (A) is FF sectional drawing in FIG. 8, (b) is GG sectional drawing in FIG. It is a top view of the sensor part in other embodiments. (A) is HH sectional drawing in FIG. 10, (b) is II sectional drawing in FIG.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the present invention is applied to a humidity sensor that detects humidity as a capacitive physical quantity detection device. FIG. 1 is a block diagram of a humidity sensor in the present embodiment.

  As shown in FIG. 1, the humidity sensor includes a sensor unit 10 and a circuit unit 20. First, the configuration of the sensor unit 10 will be briefly described. The sensor unit 10 of the present embodiment detects general humidity having the common electrode 11 and the first and second fixed electrodes 12a and 12b. 2A is a plan view of the sensor unit 10, and FIG. 2B is a cross-sectional view taken along line AA of FIG. 2A.

  As shown in FIG. 2, the sensor unit 10 is configured using a semiconductor substrate 13 such as a silicon substrate, and an insulating film 14 such as a silicon oxide film is formed on the semiconductor substrate 13. A common electrode 11 made of aluminum or the like is formed on the insulating film 14.

  On the common electrode 11, the 1st fixed electrode 12a facing the common electrode 11 via the 1st moisture sensitive member 15a from which a dielectric constant changes according to humidity is arrange | positioned, and the 1st moisture sensitive member 15a and A second fixed electrode 12b facing the common electrode 11 is disposed via a second moisture sensitive member 15b having a different way of changing the dielectric constant. That is, as shown in FIG. 1 and FIG. 2, the first capacitor portion CS1 is formed by the common electrode 11, the first moisture sensitive member 15a, and the first fixed electrode 12a, and the common electrode 11, the second moisture sensitive member 15b, A second capacitor portion CS2 is formed by the second fixed electrode 12b, and the first capacitor portion CS1 and the second capacitor portion CS2 have different sensitivity regarding humidity.

  The common electrode 11 is a fixed electrode and is an electrode that cannot be moved. Further, the first and second moisture sensitive members 15a and 15b are made of a material having a hygroscopic polymer material made of a polyimide polymer or the like, and the first and second fixed electrodes 12a and 12b are generally used. It is composed of noble metals such as aluminum and copper used in typical semiconductor processes and gold having excellent corrosion resistance. The above is the configuration of the sensor unit 10 in the present embodiment.

  The circuit unit 20 includes a circuit chip or the like, and includes a signal processing unit 30, a self-diagnosis signal application unit 40, a control unit 50, and a detection unit 60, as shown in FIG. In the present embodiment, the signal processing unit 30 corresponds to the signal processing unit of the present invention, the self-diagnosis signal application unit 40 corresponds to the self-diagnosis signal application unit of the present invention, and the control unit 50 corresponds to the first of the present invention. This corresponds to the second control means, and the detection unit 60 corresponds to the detection means of the present invention.

  The signal processing unit 30 is configured by a CV conversion circuit (switched capacitor circuit), and includes a first and second capacitor unit CS1 including a common electrode 11 and first and second fixed electrodes 12a and 12b. The difference in capacitance of CS2 is converted into a voltage and output. That is, one of the first and second capacitor units CS1 and CS2 in the sensor unit 10 constitutes the reference capacitor unit, and the signal processing unit 30 outputs a voltage corresponding to the relative humidity.

  The CV conversion circuit includes an operational amplifier 31, a capacitor 32, and a switch 33. The inverting input terminal of the operational amplifier 31 is connected to the common electrode 11 via a switch 34, and a capacitor 32 and a switch 33 are connected in parallel between the inverting input terminal and the output terminal. Further, the reference voltage V / 2 is inputted to the non-inverting input terminal of the operational amplifier 31, and the reference voltage V / 2 is applied to the common electrode 11 while the switch 34 is turned on. It has become so.

  The self-diagnosis signal application unit 40 sets the common electrode 11 to a predetermined state based on the SW control signal input from the control unit 50 during the self-diagnosis. Specifically, switches 41 and 42 that are controlled to be turned on and off by a SW control signal from the control unit 50 are provided. When the switch 41 is turned on by the control unit 50, a power supply 43 is connected to the common electrode 11. When a potential is applied and the switch 42 is turned on, a ground potential is applied to the common electrode 11.

  Note that applying a power supply potential to the common electrode 11 corresponds to applying a high-level potential to the common electrode 11 of the present invention, and applying a ground potential means, in other words, grounding the common electrode 11. In the present embodiment, the SW control signal input from the control unit 50 to the self-diagnosis signal application unit 40 corresponds to the control signal of the present invention.

  The control unit 50 applies a predetermined potential to the first and second fixed electrodes 12a and 12b and outputs an SW control signal to control the switches 33, 34, 41, and 42.

  Specifically, during normal operation, the controller 50 inputs the first fixed electrode signal P1 that periodically changes with a constant amplitude V to the first fixed electrode 12a, and the phase of the first fixed electrode signal P1 is 180 °. The second fixed electrode signal P2 that is shifted and has the same amplitude V is input to the second fixed electrode 12b.

  At the time of self-diagnosis, a high level potential or a ground potential is applied to the first and second fixed electrodes 12a and 12b every predetermined period. Furthermore, at the time of self-diagnosis, the SW control signal is output, the switch 34 is turned off to cut off the connection between the signal processing unit 30 and the sensor unit 10, and the on / off of the switches 41 and 42 is controlled. In the present embodiment, disconnecting the connection between the signal processing unit 30 and the sensor unit 10 corresponds to stopping the operation of the signal processing means of the present invention.

  The detection unit 60 is connected to the sensor unit 10 and detects whether or not there is an abnormality in the sensor unit 10 by detecting whether or not a current flows through the sensor unit 10.

  The current flows through the sensor unit 10 when the common electrode 11 and the semiconductor substrate 13 are short-circuited or when the common electrode 11 and the first and second fixed electrodes 12a and 12b are short-circuited. It is a flowing current. The above is the configuration of the humidity sensor in the present embodiment.

  Next, the operation of the humidity sensor will be described. FIG. 3 is a timing chart of the humidity sensor. Note that the potential of the common electrode 11 in FIG. 3 indicates a potential state when there is no abnormality. First, the operation during normal operation of the humidity sensor will be described.

  As shown in FIG. 3, the first fixed electrode 12a has a high-level potential (5v in FIG. 3) and a low-level potential (0V in FIG. 3 and a ground potential with a period φ1 as one cycle (for example, 10 μs). The first fixed electrode signal P1 of a rectangular wave signal with a constant amplitude that changes) is applied from the control unit 50, and the rectangular wave signal whose voltage level is inverted with respect to the first fixed electrode signal P1 is applied to the second fixed electrode 12b. The second fixed electrode signal P2 is applied from the controller 50. Further, since a voltage of V / 2 (2.5 V in FIG. 3) is applied to the non-inverting input terminal of the operational amplifier 31, a constant voltage of V / 2 is also applied to the common electrode 11.

  The switch 33 is opened and closed by the control unit 50 at the timing shown in FIG. When the switch 33 is on (period φ2), the capacitor 32 is reset. On the other hand, when the switch 33 is off, the humidity is detected. That is, a period other than the period φ2 in the period φ1 is a period for detecting humidity. In this detection period, the output voltage V0 output from the signal processing unit 30 is shown below.

(Equation 1) V0 = (CS1-CS2) .V '/ Cf + V / 2
Note that V ′ in Equation 1 is the voltage between the first and second fixed electrodes 12 a and 12 b, and Cf is the capacitance of the capacitor 32.

  When the humidity changes, the dielectric constants of the first and second moisture sensitive members 15a and 15b change, and the balance of the capacitances of the first and second capacitor parts CS1 and CS2 changes. Then, a voltage corresponding to the capacity difference (CS1-CS2) based on the above formula 1 is output as an output voltage V0 (for example, 0 to 5 V) in a form in which the output voltage of the reference humidity is added as a bias. This output voltage V0 is then signal-processed by a signal processing circuit (not shown) provided with an amplifier circuit, a low-pass filter, etc., and output as a humidity detection signal.

  Next, the operation of the humidity sensor during self-diagnosis will be described. In the humidity sensor of this embodiment, as a self-diagnosis, the first and second fixed electrodes 12a and 12b and the semiconductor substrate 13 are short-circuited, or the first and second fixed electrodes 12 and 12b and the common electrode 11 are short-circuited. It is possible to perform four items: whether the common electrode 11 and the semiconductor substrate 13 are short-circuited, or whether the first fixed electrode 12a and the second fixed electrode 12b are short-circuited. . At the time of self-diagnosis, the switch 34 is turned off by the SW control signal from the control unit 50, and the connection between the sensor unit 10 and the signal processing unit 30 is cut off.

  In the period φ3, the control unit 50 applies a high-level potential to the first and second fixed electrodes 12a and 12b, and the switches 41 and 42 are turned off. That is, the common electrode 11 is in a floating state. At this time, if at least one of the first and second fixed electrodes 12 a and 12 b is short-circuited with the semiconductor substrate 13, a current flows through the sensor unit 10. Therefore, the detection unit 60 can detect whether or not there is an abnormality in the sensor unit 10 by detecting whether or not a current flows through the sensor unit 10. The common electrode 11 is in a floating state. As shown in FIG. 3, when there is no abnormality, the common electrode 11 is attracted to the potentials of the first and second fixed electrodes 12a and 12b, and the potential becomes 5V.

  Next, in the period φ4, the control unit 50 applies a high-level potential to the first and second fixed electrodes 12a and 12b. Then, the switch 42 is turned on by the SW control signal and the ground potential is applied to the common electrode 11 from the self-diagnosis signal application unit 40. At this time, if the common electrode 11 and the first fixed electrode 12a, or the common electrode 11 and the second fixed electrode 12b are short-circuited, a current flows through the sensor unit 10. Therefore, the detection unit 60 can detect whether or not there is an abnormality in the sensor unit 10 by detecting whether or not a current flows through the sensor unit 10.

  Subsequently, in the period φ5, the control unit 50 applies a high-level potential to the first and second fixed electrodes 12a and 12b. Then, the switch 41 is turned on by the SW control signal and the power supply potential is applied to the common electrode 11 from the self-diagnosis signal application unit 40. At this time, if the common electrode 11 is short-circuited with the semiconductor substrate 13, a current flows through the sensor unit 10. Therefore, the detection unit 60 can detect whether or not there is an abnormality in the sensor unit 10 by detecting whether or not a current flows through the sensor unit 10.

  In the period φ6, the control unit 50 applies a high level potential to the first fixed electrode 12a, applies a ground potential to the second fixed electrode 12b, and turns off the switches 41 and 42. That is, the common electrode 11 is in a floating state. At this time, if the first fixed electrode 12 a and the second fixed electrode 12 b are short-circuited, a current flows through the sensor unit 10. Therefore, the detection unit 60 can detect whether or not there is an abnormality in the sensor unit 10 by detecting whether or not a current flows through the sensor unit 10. The common electrode 11 is in a floating state. As shown in FIG. 3, when there is no abnormality, the common electrode 11 is attracted to the intermediate potential between the first and second fixed electrodes 12a and 12b and the potential is 2.5V. It becomes.

  The above is the operation of the humidity sensor in the present embodiment. Here, the example in which the self-diagnosis is performed in all the periods φ3 to φ6 has been described. However, for example, when the detection unit 60 detects an abnormality of the sensor unit 10 in the period φ3 (the sensor unit 10 has a current) In the case where it is detected that an error is flowing, a signal indicating that an abnormality has been detected may be input to the control unit 50 so that the self-diagnosis after the period φ4 is not performed.

  As described above, in the present embodiment, the sensor is obtained by applying a predetermined potential to the first and second fixed electrodes 12a and 12b, setting the common electrode 11 in a predetermined state, and detecting the current flowing through the sensor unit 10. An abnormality of the unit 10 is detected. For this reason, self-diagnosis can be performed even in a humidity sensor or the like having no movable electrode.

(Other embodiments)
In the first embodiment, in the period φ4, the ground potential can be applied from the control unit 50 to the first and second fixed electrodes 12a and 12b. In this case, the switch 41 is turned on by the SW control signal to the common electrode 11 so that the power supply voltage is applied from the self-diagnosis signal application unit 40, and the current flowing through the sensor unit 10 is detected by the detection unit 60. Thus, it is possible to detect whether the common electrode 11 and the first fixed electrode 12a or the common electrode 11 and the second fixed electrode 12b are short-circuited.

  Similarly, in the first embodiment, a ground potential can be applied from the control unit 50 to the first and second fixed electrodes 12a and 12 in the period φ5. In this case, the switch 42 is turned on by the SW control signal to the common electrode 11 so that the ground potential is applied from the self-diagnosis signal application unit 40, and the current flowing through the sensor unit 10 is detected by the detection unit 60. Thus, it is possible to detect whether or not the common electrode 11 and the semiconductor substrate 13 are short-circuited.

  Furthermore, in the first embodiment, in the period φ6, the control unit 50 may apply a ground potential to the first fixed electrode 12a and apply a high-level potential to the second fixed electrode 12b.

  In the first embodiment, for example, the present invention may be applied to a humidity sensor having the sensor unit 10 in which the first and second fixed electrodes 12a and 12b and the common electrode 11 are formed in a comb-teeth shape. it can. 4 is a plan view of the sensor unit 10 according to another embodiment, FIG. 5A is a cross-sectional view taken along the line BB in FIG. 4, and FIG. 5B is a cross-sectional view taken along the line CC in FIG.

  4 and FIG. 5, an insulating film 14 is formed on a semiconductor substrate 13, and a common electrode 11 and first and second fixed electrodes 12 a and 12 b are formed on the insulating film 14. . Specifically, the common electrode 11 and the first and second fixed electrodes 12a and 12b are formed so that their comb teeth portions face each other. The interval between the common electrode 11 and the first fixed electrode 12a is narrower than the interval between the common electrode 11 and the second fixed electrode 12b. A protective film 16 is formed so as to cover the common electrode 11, the first and second fixed electrodes 12 a and 12 b, and a moisture sensitive member 15 is formed on the protective film 16.

  Also in such a sensor unit 10, since the interval between the common electrode 11 and the first fixed electrode 12a is narrower than the interval between the common electrode 11 and the second fixed electrode 12b, the first capacitor unit CS1 and the second capacitor The sensitivity with the part CS2 can be different from each other.

  Further, the sensor unit 10 as shown in FIGS. 6 and 7 may be used. That is, the first moisture sensitive member 15a is disposed on the protective film 16 covering the common electrode 11 and the first fixed electrode 12a, and the second moisture sensitive material is disposed on the protective film 16 covering the common electrode 11 and the second fixed electrode 12b. The member 15b may be arranged. Even in such a sensor unit 10, since the first moisture-sensitive member 15a and the second moisture-sensitive member 15b have different ways of changing the dielectric constant with respect to humidity, the sensitivity of the first capacitor unit CS1 and the second capacitor unit CS2 is different. The sensor units 10 can be different from each other. In the sensor unit 10, the interval between the common electrode 11 and the first fixed electrode 12a is equal to the interval between the common electrode 11 and the second fixed electrode 12b, but the common electrode 11 and the second fixed electrode 12b are the same. It may be narrower than the interval.

  Further, the sensor unit 10 as shown in FIGS. 8 and 9 may be used. That is, with respect to the sensor unit 10 shown in FIGS. 6 and 7, the second moisture sensitive member 15b may not be disposed on the protective film 16 covering the common electrode 11 and the second fixed electrode 12b. Such a sensor unit 10 can also be a sensor unit 10 in which the sensitivity of the first capacitor unit CS1 and the second capacitor unit CS2 is different from each other.

  In the first embodiment, when all diagnoses in the period φ3 to the period φ6 are performed, the order in which the diagnosis is performed can be appropriately changed.

  In the first embodiment, the example in which the circuit unit 20 includes the signal processing unit 30, the self-diagnosis signal application unit 40, the control unit 50, and the detection unit 60 has been described, but these are provided in separate circuit units. It may be done. For example, when mounted on a vehicle, the vehicle ECU may be configured to perform the functions of the signal processing unit 30, the self-diagnosis signal application unit 40, the control unit 50, and the detection unit 60.

  Furthermore, in the first embodiment, the humidity sensor that detects the humidity is described as an example of the capacitive physical quantity detection device. However, the present invention is applicable to the detection of materials having dielectric properties such as oil, alcohol, gasoline, and organic solvents. Can be applied.

  As shown in FIGS. 10 and 11, the sensor unit 10 is configured by removing the protective film 16 and the first and second moisture sensitive members 15 a and 15 b from the sensor unit 10 shown in FIGS. 4 and 5. Yes. The intervals between the common electrode 11 and the first fixed electrode 12a and the common electrode 11 and the second fixed electrode 12b are different. According to this, since the capacitance between the common electrode 11 and the first fixed electrode 12a and the common electrode 11 and the second fixed electrode 12b varies depending on the material having dielectric characteristics, the material having dielectric characteristics can be detected. it can.

  Furthermore, for example, the present invention can be applied to the case where the common electrode 11 is a movable electrode, such as an acceleration sensor or an angular velocity sensor.

DESCRIPTION OF SYMBOLS 10 Sensor part 11 Common electrode 12a 1st fixed electrode 12b 2nd fixed electrode 13 Semiconductor substrate 20 Circuit part 30 Signal processing part 40 Self-diagnosis signal application part 50 Control part 60 Detection part

Claims (8)

A sensor unit (1) configured using a semiconductor substrate (13) and having a first and second fixed electrodes (12a, 12b) and a common electrode (11) facing the first and second fixed electrodes (12a, 12b). 10) and
First control means (50) for applying a predetermined potential to the first and second fixed electrodes (12a, 12b) and outputting a predetermined control signal during self-diagnosis;
Self-diagnosis signal applying means (40) for setting the common electrode (11) in a predetermined state based on the control signal from the first control means (50) during self-diagnosis;
Detecting means (60) for detecting a current flowing through the sensor unit (10) during self-diagnosis,
At the time of self-diagnosis, a predetermined potential is applied from the first control means (50) to the first and second fixed electrodes (12a, 12b), and the common electrode (11) is applied to the self-diagnosis signal application means (40). ) And a self-diagnosis means (40-60) for detecting an abnormality of the sensor section (10) by detecting a current flowing through the sensor section (10) by the detection means (60). Capacitive physical quantity detection device characterized by the above. The self-diagnosis means (40-60)
Applying a high level potential higher than the ground potential from the first control means (50) to the first and second fixed electrodes (12a, 12b),
The capacitive physical quantity detection device according to claim 1, wherein the common electrode (11) is brought into a floating state by the self-diagnosis signal applying means (40). The self-diagnosis means (40-60)
Applying a high level or ground potential higher than the ground potential from the first control means (50) to the first and second fixed electrodes (12a, 12b),
When the high level potential is applied to the common electrode (11) to the first and second fixed electrodes (12a, 12b), a ground potential is applied by the self-diagnosis signal applying means (40). When a ground potential is applied to the first and second fixed electrodes (12a, 12b), a high level potential higher than the ground potential is applied by the self-diagnosis signal applying means (40). The capacity type physical quantity detection device according to claim 1 or 2. The self-diagnosis means (40-60)
Applying a high level or ground potential higher than the ground potential from the first control means (50) to the first and second fixed electrodes (12a, 12b),
When the high-level potential is applied to the common electrode (11) to the first and second fixed electrodes (12a, 12b), the self-diagnosis signal applying means (40) causes the high potential to be higher than the ground potential. When a potential of a level is applied and a ground potential is applied to the first and second fixed electrodes (12a, 12b), the ground potential is applied by the self-diagnosis signal applying means (40). The capacity type physical quantity detection device according to any one of claims 1 to 3. The self-diagnosis means (40-60)
A high level potential higher than the ground potential is applied to one of the first and second fixed electrodes (12a, 12b) from the first control means (50), and a ground potential is applied to the other,
The capacitive physical quantity detection device according to any one of claims 1 to 4, wherein the common electrode (11) is brought into a floating state by the self-diagnosis signal applying means (40). A signal processing means (30) connected to the sensor section (10) for processing a signal from the sensor section (10);
Capacitive physical quantity detection according to any one of claims 1 to 5, further comprising second control means (50) for stopping the operation of the signal processing means (30) during self-diagnosis. apparatus.   The capacitive physical quantity detection device according to any one of claims 1 to 6, wherein the sensor unit (10) detects humidity. The capacitive physical quantity detection device according to any one of claims 1 to 6, wherein the sensor unit (10) detects a material having dielectric characteristics.

Images