JP2012037341A - Electrostatic capacitance type acceleration detection apparatus and calibration method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calibration function for adjusting sensitivity and adjusting offset by accurately detecting an electrostatic capacitance between detection electrodes disposed while opposing a weight.SOLUTION: A capacitance/voltage conversion circuit 403 includes a function for converting a capacitance between one detection electrode and a weight and a capacitance between another detection electrode and the weight into a voltage, and a function for converting a difference between the capacitance between the one detection electrode and the weight and the capacitance between the other detection electrode and the weight into a voltage. An EEPROM 410 stores a sensitivity correction value and an offset correction value. A variable gain amplifier 404 adjusts an output from the capacitance/voltage conversion circuit 403 on the basis of the sensitivity correction value. An offset correction circuit 406 adjusts an output from a demodulation circuit 405 on the basis of the offset correction value. A digital interface 408 writes the sensitivity correction value and the offset correction value into the EEPROM 410.

Description

  The present invention relates to a capacitance type acceleration detection apparatus having a calibration function for performing sensitivity adjustment and offset adjustment using Coulomb force, and a calibration method thereof.

  In general, a device for detecting a physical quantity using a change in the distance between electrodes and an operation test method thereof are well known. For example, a detection device having a simple structure in which two substrates are arranged to face each other and electrodes are formed on the respective substrates is known. In this detection device, one substrate is displaced based on a physical quantity such as acceleration, the distance between the electrodes formed on both substrates is changed by this displacement, and this is detected as a change in capacitance between both electrodes. ing. In addition, this detection device can be used as an acceleration detection device that detects the applied acceleration if a weight body is bonded to one substrate and the substrate is displaced based on the acceleration applied to the weight body. Is.

  Usually, when a detection device of some physical quantity is commercialized, it is necessary to perform an operation test as to whether or not this detection device outputs a correct detection signal. Conventionally, in such an operation test, a method has been adopted in which a physical quantity to be detected is actually applied to the detection device and a detection signal at that time is examined. For example, in the case of an acceleration detection device, whether or not an acceleration of a predetermined magnitude is actually applied to the detection device from a predetermined direction, and the detection signal at that time is correct according to the applied acceleration. Determine.

  As this type of acceleration detection device, for example, those disclosed in Patent Documents 1 and 2 have been proposed. The acceleration detection device described in Patent Document 1 is a gravitational acceleration in each detection axis direction when measuring electrical characteristics of an acceleration sensor capable of measuring acceleration in three orthogonal axes (X axis, Y axis, and Z axis). The present invention relates to an acceleration generating device for applying a voltage and an acceleration sensor measuring device using the same.

  In addition, the acceleration detection device described in Patent Document 2 is equipped with a triaxial acceleration sensor that detects triaxial acceleration components orthogonal to each other and outputs an acceleration component signal, and a triaxial acceleration sensor. A measurement plate for measuring an acceleration detection signal of the acceleration sensor, a support plate for rotating and supporting the measurement plate, and a main rotation shaft for rotating the support plate are provided.

  However, in order to perform such an operation test, a dedicated test facility is required, and the test work is complicated and time-consuming. In particular, the quantity that can be tested with a dedicated test facility is limited, leading to a decrease in productivity. Therefore, such a conventional test method has a problem that it is not suitable as an operation test for a mass-produced apparatus.

  Thus, for example, an acceleration sensor inspection device and an operation test method thereof have been proposed as disclosed in Patent Document 3. In this patent document 3, a displacement electrode supported so as to be able to be displaced by the action of an external force, a fixed electrode fixed to an apparatus housing at a position facing the displacement electrode, and a distance between these electrodes. An acceleration detecting device operation test method for detecting an acceleration corresponding to an external force as an electrical signal, wherein a predetermined voltage is applied between both electrodes, and the applied voltage In the state where the displacement electrode is displaced by the Coulomb force generated based on the electric signal, an electric signal having a temporal variation component having a predetermined magnitude is given to one electrode of both electrodes, and transmitted to the other electrode at this time By comparing the magnitude of the fluctuation component to be applied with the applied voltage, the operation of this detection device is tested, and the acceleration detection device that detects the acceleration using the change in the distance between the electrodes is used. It is a work test method.

  In addition, a device for detecting a physical quantity using other changes in the distance between electrodes and its operation test method, that is, applying a voltage to the test electrode and displacing it by Coulomb force, the magnitude of the applied voltage and the amount of displacement (capacity change) For example, Patent Documents 4 and 5 have been proposed for performing an operation test in comparison with (1).

Japanese Patent Laid-Open No. 10-002914 JP 2007-322337 A JP 2002-221463 A International Publication WO1992 / 17759 JP 2000-146729 A

  However, the above-described inspection apparatus and its operation test method have a problem that basically only a rough operation test such as failure detection can be performed. This is because when the acceleration sensor is calibrated with respect to variations in sensitivity and offset, the Coulomb force itself used as a reference varies due to variations in the shape of the acceleration sensor, and thus the sensitivity and offset cannot be accurately calibrated.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a capacitance between a displaceable weight body and a detection electrode disposed opposite to the weight body. It is an object of the present invention to provide a capacitance type acceleration detection apparatus having a calibration function for accurately detecting and adjusting sensitivity and offset and a calibration method thereof.

  The present invention has been made in order to achieve such an object, and the invention according to claim 1 is provided with a displaceable weight body and a counterweight body, and the weight body. A capacitance-type acceleration sensor having a plurality of pairs of detection electrodes in which the capacitance between one detection electrode and the weight body increases and the capacitance between the other detection electrode and the weight body decreases. In the capacitive acceleration detection device for adjusting sensitivity and offset, an electrode selection means for selecting a pair of detection electrodes from the plurality of pairs of detection electrodes included in the capacitive acceleration sensor, and the electrode selection means Capacitance detection means for detecting the capacitance between the one detection electrode and the other detection electrode of the selected pair of detection electrodes and the weight body, and the pair of detection electrodes selected by the electrode selection means Said one detection electrode and front Voltage application means for applying a voltage to the other detection electrode; storage means for holding a sensitivity correction value and an offset correction value obtained from the capacitance detected by the capacitance detection means and the voltage applied to the detection electrode; And a sensitivity adjustment unit that performs sensitivity adjustment according to the correction value held by the storage unit, and an offset adjustment unit that performs offset adjustment using the correction value held by the storage unit.

  According to a second aspect of the present invention, in the first aspect of the present invention, the capacitive acceleration sensor includes a plurality of capacitive acceleration sensors having the same thickness of the weight body. And

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the voltage application means includes a voltage generation source, and a voltage generated by the voltage generation source is applied to the detection electrode. It is characterized by.

  According to a fourth aspect of the present invention, in the first, second, or third aspect of the invention, the voltage applying unit applies a voltage supplied from the outside to the detection electrode.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the capacitance detection means includes the one detection electrode and the weight of the selected pair of detection electrodes. A function of converting the capacitance between the bodies into voltage, a function of converting the capacitance between the other detection electrode and the weight body into a voltage, a capacitance between the one detection electrode and the weight body, and the other It has a function of converting a difference between a capacitance between the detection electrode and the weight body into a voltage.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the capacitance detecting means individually detects two capacitances, and the single-ended capacitance-voltage conversion circuit. A differential amplifier circuit that outputs a difference in output voltage from the voltage conversion circuit; and a selector that selects one output from the output from the single-ended capacitance voltage conversion circuit and the output from the differential amplifier circuit. It is characterized by.

  The invention described in claim 7 is characterized in that in the invention described in any one of claims 1 to 6, a parasitic capacitance removing unit is added to the sensitivity adjusting unit.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the capacitive acceleration sensor includes a comb-shaped X-axis capacitive acceleration sensor and a comb. It is a capacitive three-axis acceleration sensor in which a tooth-type Y-axis capacitive acceleration sensor and a seesaw-type Z-axis capacitive acceleration sensor are integrally formed.

  The invention described in claim 9 is the weight of the comb-shaped X-axis capacitive acceleration sensor and the comb-shaped Y-axis capacitance according to the invention described in claim 8. The weight of the acceleration sensor is the same.

  Further, the invention according to claim 10 is provided with a displaceable weight body and the weight body, and the capacitance of one detection electrode and the weight body is caused by the displacement of the weight body. A capacitance-type acceleration sensor that includes a plurality of capacitance-type acceleration sensors each having a pair of detection electrodes that increase and the capacitance between the other detection electrode and the weight body decreases, and detects a difference between the pair of capacitances In a calibration method for adjusting sensitivity and offset in the apparatus, a step of applying a reference voltage to one detection electrode facing the weight body to detect a capacitance between the other detection electrode and the weight body; A step of applying a voltage different from the reference voltage to one of the detection electrodes to detect a capacitance between the other detection electrode and the weight body, and performing a sensitivity adjustment by obtaining a sensitivity correction value from the detected capacitance Step and said one detection electrode A step of detecting a capacitance difference between the detected capacitance between the weight bodies and a detected capacitance between the other detection electrode and the weight body; and obtaining an offset correction value from the detected capacitance difference. And an offset correction step.

  The invention according to claim 11 is characterized in that, in the invention according to claim 10, the step of adjusting the sensitivity obtains a sensitivity correction value by removing parasitic capacitance from the detected capacitance. .

  Further, in the invention described in claim 12, in the invention described in claim 10 or 11, the step of adjusting the sensitivity may be performed by multiplying the sensitivity correction value by a difference between gravity and Coulomb force as a coefficient. It is used as a sensitivity correction value.

  According to a thirteenth aspect of the present invention, in the invention according to the tenth, eleventh or twelfth aspect, the step of performing the offset correction is based on a distribution of capacitance values obtained from a plurality of capacitive acceleration sensors. A sensitivity correction value is obtained.

  According to a fourteenth aspect of the present invention, in the invention according to the tenth, eleventh or twelfth aspect, the step of performing the sensitivity adjustment includes a capacitance change with respect to gravity obtained from a plurality of capacitive acceleration sensors, The sensitivity correction value is obtained from the relationship with the capacitance change due to voltage.

  According to the present invention, the displaceable weight body and the weight body are provided opposite to the weight body. The displacement of the weight body increases the capacitance between one detection electrode and the weight body, and the other detection body. A capacitive acceleration sensor having a capacitance type acceleration sensor having a plurality of pairs of detection electrodes whose capacitance between the electrode and the weight body decreases, and adjusting the sensitivity and offset. Electrode selecting means for selecting a pair of detection electrodes from a plurality of pairs of detection electrodes provided, one detection electrode of the pair of detection electrodes selected by the electrode selection means, and a capacitance between the other detection electrode and the weight body Capacitance detection means for detecting, voltage application means for applying a voltage to one detection electrode and the other detection electrode of a pair of detection electrodes selected by the electrode selection means, and capacitance and detection electrodes detected by the capacitance detection means Applied power Storage means for holding the sensitivity correction value and offset correction value obtained from the above, a sensitivity adjustment means for adjusting sensitivity according to the correction value held by the storage means, and an offset by the correction value held by the storage means Since the offset adjusting means for adjusting is provided, it is possible to provide a capacitance type acceleration detecting device having a calibration function for adjusting sensitivity and adjusting offset and a calibration method thereof.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram for demonstrating the electrostatic capacitance type acceleration sensor which concerns on this invention, (a) is a top view, (b) is the sectional view on the AA 'line of (a), (c) is (a). It is a BB 'line sectional view. It is a block diagram for demonstrating the other capacitive acceleration sensor which concerns on this invention, (a) is a perspective view, (b) is the sectional view on the AA 'line of (a), (c) is an electrode. It is a top view. BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram for demonstrating the capacitive acceleration sensor which concerns on this invention, (a) is a top view, (b) is the sectional view on the A-A 'line of (a). It is a block diagram for demonstrating the capacitance-type acceleration detection apparatus provided with the calibration function which concerns on this invention. FIG. 5 is a circuit diagram illustrating a configuration example of the capacitance-voltage conversion circuit described in FIG. 4. It is a principle figure for demonstrating the sensitivity adjustment method of the electrostatic capacitance type acceleration sensor for a X, Y-axis direction detection used for the electrostatic capacitance type acceleration detection apparatus provided with the calibration function which concerns on this invention. It is a principle figure for demonstrating the sensitivity adjustment method of the capacitive acceleration sensor for a Z-axis direction detection used for the capacitive acceleration detection apparatus provided with the calibration function which concerns on this invention. FIG. 6 is a distribution diagram of capacitance values for a plurality of capacitive acceleration sensors. FIG. 6A is a distribution diagram showing the relationship between the capacitance change due to gravity and the capacitance change due to voltage. FIG. 5A shows an example in which the thickness t of the weight body varies and d is almost constant, and FIG. In the example, the thickness t is substantially constant and the gap d varies. It is a figure which shows the flowchart for demonstrating the calibration method in the electrostatic capacitance type acceleration detection apparatus provided with the calibration function which concerns on this invention. FIG. 6 is a specific process diagram (part 1) of the sensitivity and offset correction method using the capacitance type acceleration detection device having the calibration function according to the present invention shown in FIG. FIG. 5 is a specific process diagram (part 2) of the sensitivity and offset correction method using the capacitance type acceleration detection device having the calibration function according to the present invention shown in FIG. FIG. 5 is a specific process diagram (part 3) of the sensitivity and offset correction method using the capacitance type acceleration detection apparatus having the calibration function according to the present invention shown in FIG. FIG. 6 is a specific process diagram (part 4) of the sensitivity and offset correction method using the capacitance type acceleration detection apparatus having the calibration function according to the present invention shown in FIG. 4; FIG. 6 is a specific process diagram (part 5) of the sensitivity and offset correction method using the capacitance type acceleration detection apparatus having the calibration function according to the present invention shown in FIG. FIG. 6 is a specific process diagram (part 6) of the sensitivity and offset correction method using the capacitance type acceleration detection device having the calibration function according to the present invention shown in FIG. FIG. 7 is a specific process diagram (No. 7) of the sensitivity and offset correction method using the capacitance type acceleration detection device having the calibration function according to the present invention shown in FIG. FIG. 8 is a specific process diagram (No. 8) of the sensitivity and offset correction method using the capacitance type acceleration detection apparatus having the calibration function according to the present invention shown in FIG. FIG. 9 is a specific process diagram (No. 9) of the sensitivity and offset correction method using the capacitance type acceleration detection device having the calibration function according to the present invention shown in FIG. FIG. 10 is a specific process chart (No. 10) of the sensitivity and offset correction method using the capacitance type acceleration detection apparatus having the calibration function according to the present invention shown in FIG. FIG. 11 is a specific process diagram (No. 11) of the sensitivity and offset correction method using the capacitance type acceleration detection apparatus having the calibration function according to the present invention shown in FIG. 4. FIG. 10 is a specific process diagram (No. 12) of the sensitivity and offset correction method using the capacitance type acceleration detection apparatus having the calibration function according to the present invention shown in FIG. 4. FIG. 13 is a specific process diagram (No. 13) of the sensitivity and offset correction method using the capacitance type acceleration detection apparatus having the calibration function according to the present invention shown in FIG. 4. FIG. 15 is a specific process diagram (No. 14) of the sensitivity and offset correction method using the capacitance type acceleration detection apparatus having the calibration function according to the present invention shown in FIG. 4. FIG. 15 is a specific process diagram (No. 15) of the sensitivity and offset correction method using the capacitance type acceleration detection apparatus having the calibration function according to the present invention shown in FIG. 4. It is a block diagram for demonstrating the other Example of the capacitive acceleration sensor which concerns on this invention, (a) is a top view, (b) is the sectional view on the AA 'line of (a), (c). FIG. 4 is a sectional view taken along line BB ′ in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIGS. 1A to 1C are configuration diagrams for explaining a capacitive acceleration sensor according to the present invention. FIG. 1A is a top view and FIG. 1B is FIG. FIG. 1C is a cross-sectional view taken along the line BB ′ of FIG. 1A.

  This capacitive acceleration sensor is a comb-shaped capacitive acceleration sensor 10, which is a displaceable weight body 16, comb-shaped movable electrodes 17a to 17f coupled to the weight body 16, and combs. The fixed electrodes 13a to 13f and the fixed electrodes 14a to 14f arranged opposite to each other with the tooth movable electrodes 17a to 17f interposed therebetween, the beam members 12a to 12d connected to the weight body 16, and the beam members 12a and 12c. A fixed anchor 11a, a fixed anchor 11b coupled to the beam members 12b and 12d, and a substrate 15 that supports the fixed anchors 11a and 11b are provided. The comb-shaped movable electrodes 17a and 17f and one detection electrode (fixed electrodes 13a and 13f) are provided. ) And a change in capacitance between the movable electrode 17a and 17f and the other detection electrode (fixed electrode 14a and 14f). It has been. In addition, the code | symbol L shows the area | region of the comb-tooth movable electrode facing a fixed electrode, and d has shown the space | interval of a fixed electrode and a comb-tooth movable electrode.

  A capacitive acceleration detecting device having an operation test function can be configured for such a comb-teeth capacitive acceleration sensor 10, and comb movable electrodes 17a to 17f of the weight body 16 generated by Coulomb force. In addition, a highly accurate operation test can be performed by a change in capacitance generated between the fixed electrodes 13a and 13f or the fixed electrodes 14a and 14f.

  2A to 2C are configuration diagrams for explaining another capacitive acceleration sensor according to the present invention. FIG. 2A is a perspective view, and FIG. 2B is FIG. FIG. 2A is a cross-sectional view taken along line AA ′ in FIG. 2A, and FIG. 2C is a top view of the electrode.

This capacitance type acceleration sensor is a seesaw type capacitance type acceleration sensor 20, which includes a displaceable weight body 26, beam members 22a to 22b coupled to the weight body 26, and the beam member. A fixed anchor 21 coupled to 22a to 22b, a substrate 25 supporting the fixed anchor 21, a left detection fixed electrode 23 disposed on the substrate and facing the weight body 26, and a fixed anchor 21 A right detection fixed electrode 24 facing the weight body 26, and a capacitance change between the weight body 26 and the left detection fixed electrode 23 and a capacitance change between the weight body 26 and the right detection fixed electrode 24. Configured to detect. Reference numeral L1 denotes a distance between the center position of the fixed anchor 21 and one end of the fixed electrode, L2 denotes a distance between the center position of the fixed anchor 21 and the other end of the fixed electrode, and W _E denotes a width of the fixed electrode.

  FIGS. 3A and 3B are configuration diagrams for explaining the capacitive acceleration sensor according to the present invention. FIG. 3A is a top view and FIG. 3B is FIG. It is AA 'line sectional drawing of.

  This capacitive acceleration sensor includes a comb-shaped capacitive acceleration sensor 10X in which the comb-shaped capacitive acceleration sensor 10 shown in FIG. 1 is arranged for the X-axis, and the configuration shown in FIG. A comb-teeth capacitive acceleration sensor 10Y having a comb-teeth capacitive acceleration sensor 10 arranged for the Y-axis and a seesaw-type capacitive acceleration sensor 20 shown in FIG. This is a capacitance type triaxial acceleration sensor 30 that is integrally configured with a seesaw type capacitance type acceleration sensor 20Z.

  That is, a capacitive acceleration sensor 10X for detecting the acceleration in the X-axis direction, a capacitive acceleration sensor 10Y for detecting the acceleration in the Y-axis direction, and an acceleration for detecting the acceleration in the Z-axis direction. The capacitive acceleration sensor 20Z is configured on the same plane, and the thicknesses of the three weight bodies 16X, 16Y, and 26Z constituting the capacitive three-axis acceleration sensor are all equal. Reference numeral 31 denotes a frame, 32 denotes a substrate, and t denotes the thickness of the weight body 26Z.

  With such a configuration, the acceleration in the X-axis direction is detected by a change in capacitance between the comb-shaped movable electrode coupled to the weight body 16X in the X-axis capacitive acceleration sensor 10X and the fixed electrode, and the Y-axis direction. Is detected by a change in capacitance between the comb-shaped movable electrode coupled to the weight body 16Y in the Y-axis capacitive acceleration sensor 10Y and the fixed electrode, and the acceleration in the Z-axis direction is the static acceleration for the Z-axis. The capacitance change between the weight body 26Z and the left and right fixed electrodes in the capacitive acceleration sensor 20Z is detected.

  FIG. 4 is a block diagram for explaining a capacitance type acceleration detection apparatus having a calibration function according to the present invention. The capacitance type triaxial acceleration sensor 30 includes comb-tooth type capacitance acceleration sensors 10X and 10Y for detecting X and Y axis direction accelerations and a seesaw type capacitance acceleration sensor for detecting Z axis direction accelerations. 20Z is provided. The capacitive acceleration sensors 10X and 10Y each include one detection electrode composed of one comb-shaped movable electrode and a fixed electrode, and the other detection electrode composed of the other comb-shaped movable electrode and the fixed electrode. ing. Similarly, the capacitive acceleration sensor 20Z includes one detection electrode and the other detection electrode. The calibration function performs sensitivity adjustment and offset adjustment. More specifically, sensitivity adjustment refers to the variation of the capacitance change for each constant acceleration even if the capacitance acceleration sensor has a variation in the capacitance change. Adjustment is made so that the output becomes constant. Further, the offset adjustment is to make an adjustment so that the output of the capacitive acceleration detecting device becomes zero when no acceleration is applied to the capacitive acceleration sensor.

  The multiplexer (electrode selection means) 401 selects a pair of detection electrodes belonging to one of the three capacitive acceleration sensors for X, Y, and Z-axis direction acceleration detection. The capacitance-voltage conversion circuit (capacitance detection means) 403 has a function of converting the capacitance between one detection electrode and the weight body of the pair of detection electrodes selected by the multiplexer 401 into a voltage, and the other detection electrode. It has the function of converting the capacitance between the weights into a voltage, and the function of converting the difference between the capacitance between one detection electrode and the weight body and the capacitance between the other detection electrode and the weight body into a voltage. .

  A specific circuit diagram is shown in FIG. 5 described later. Further, as compared with the case where each of the X, Y, and Z axes has a separate capacitance / voltage conversion circuit, the multiplexer 401 and the single capacitance / voltage conversion circuit 403 are used in this way, and the X, Y, and Z axes are time-shared. When measuring the direction acceleration, since the same capacitance-voltage conversion circuit is used, a relative measurement error between the X, Y, and Z axes can be reduced.

  The voltage source 402 is for generating a voltage to be applied to the detection electrode selected by the multiplexer 401. The EEPROM 410 is a memory for writing and storing sensitivity correction values and offset correction values. The variable gain amplifier (sensitivity adjusting means) 404 is for adjusting the output from the capacitance / voltage conversion circuit 403 based on the sensitivity correction value. In addition, when adjusting the sensitivity, in addition to the capacitance of the opposing portion of the detection electrode and the weight body, the parasitic capacitance generated at the detection electrode and the weight body other than the opposing portion of the detection electrode and the weight body, There is a parasitic capacitance generated in the wiring connecting the capacitive acceleration sensor and the circuit, and it is desirable to eliminate the influence of these parasitic capacitances. For this purpose, it is necessary to estimate the influence of the parasitic capacitance in advance by simulation and to take this into consideration to obtain the sensitivity correction value. In addition, it is desirable to remove the influence resulting from the difference between gravity and Coulomb force, which will be described later. For this purpose, it is necessary to estimate the effect in advance by simulation in the same manner as the effect of the parasitic capacitance, and to calculate the sensitivity correction value in consideration of this. By adjusting the variable gain amplifier 404 based on the sensitivity correction value thus obtained, it is possible to remove the influence of the parasitic capacitance and the influence caused by the difference between the gravity and the Coulomb force. That is, the variable gain amplifier 404 can be used as a parasitic capacitance removing unit and an effect removing unit that is caused by the difference between gravity and Coulomb force.

  The oscillation circuit 409 is for applying a high-frequency voltage to the three weight bodies included in the capacitive triaxial acceleration sensor 30. The demodulation circuit 405 is for demodulating the output from the variable gain amplifier 404 that has been modulated to a high frequency into a direct current. The offset correction circuit (offset adjustment means) 406 is for adjusting the output from the demodulation circuit 405 based on the offset correction value. The analog / digital converter 407 is for converting the output voltage from the demodulation circuit 405 into a digital value.

  The digital interface 408 transmits analog / digital conversion circuit output to an external device having an arithmetic processing function, receives a command from the external device, and writes a sensitivity correction value and an offset correction value to the EEPROM 410. It is. In addition, the variable gain amplifier 404 and the offset correction circuit 406 are set based on the sensitivity correction value and the offset correction value.

  As an external device having an arithmetic processing function, a semiconductor tester for inspecting a capacitance type acceleration detection device, or a microcontroller that controls the capacitance type acceleration detection device mounted on an electronic device such as a mobile phone. Can be considered.

  How the calibration function is realized by such a configuration will be described in detail with reference to FIG. 11 described later. That is, after performing such calibration, the capacitive acceleration detection device of the present invention measures the capacitance difference between one and the other detection electrodes under a certain state of the multiplexer 401, and X, Y , Z-axis direction acceleration can be detected, and the output can be taken out from the digital interface 408 as a capacitance value.

  FIG. 5 is a circuit diagram illustrating a configuration example of the capacitance-voltage conversion circuit described in FIG. The capacitance-voltage conversion circuit 403 includes single-end capacitance-voltage conversion circuits 51a and 51b that individually detect two capacitors, and a differential amplifier circuit 52 that outputs a difference between output voltages from the single-end capacitance-voltage conversion circuits 51a and 51b. And a selector 53 that selects one output from the outputs from the single-end capacitance voltage conversion circuits 51a and 51b and the output from the differential amplifier circuit 52.

  With this configuration, as described above, the capacitance-voltage conversion circuit 403 has a function of converting a capacitance between one detection electrode and the weight body among the pair of detection electrodes selected by the multiplexer 401 into a voltage, The function of converting the capacitance between the other detection electrode and the weight body into a voltage and the difference between the capacitance between one detection electrode and the weight body and the capacitance between the other detection electrode and the weight body is converted into a voltage. With functionality.

  FIGS. 6A to 6E show a sensitivity adjustment method for a capacitive acceleration sensor for detecting the X- and Y-axis directions used in the capacitive acceleration detecting device having a calibration function according to the present invention. It is a principle diagram for explaining. Here, a sensitivity adjustment method for the X-axis direction acceleration detection comb-shaped capacitive acceleration sensor 10X will be described. Reference numeral 60L denotes one detection electrode, which corresponds to 13a to 13f in FIG. 1, and 60R denotes the other detection electrode, which corresponds to 14a to 14f in FIG.

First, FIG. 6A shows a normal acceleration detection state in which a capacitance change due to gravitational acceleration is detected. From the gravity M · g applied to the weight body 16X having the mass M and the capacitance change due to the gravity M · g, the capacitance change per force k _g [F / N] can be expressed as follows.

Here, C _LX represents a capacitance between one detection electrode 60L and the weight body 16X, and C _RX represents a capacitance between the other detection electrode 60R and the weight body 16X.

On the other hand, the capacity change k _c [F / N] per force can also be obtained by using Coulomb force instead of gravity. This will be described with reference to FIGS. 6B to 6E. First, as shown in FIG. 6B, the capacitance C _RX0 between the other detection electrode 60R and the weight body 16X is detected with the reference voltage VCOM applied to the one detection electrode 60L. Next, as shown in FIG. _6C , the capacitance C _RXd between the other detection electrode 60R and the weight body 16X is detected in a state where the voltage VDD is applied to the one detection electrode 60L. The Coulomb force F _CL acting between the other detection electrode 60R to which VDD is added and the weight body 16X can be expressed as follows.

  S represents an area where the detection electrode and the weight body overlap, d represents a gap between the detection electrode and the weight body, and N represents the number of sets of the fixed electrode and the movable electrode of the capacitive acceleration sensor 10X. , L represents the length at which the fixed electrode and the movable electrode overlap.

Next, as shown in FIG. _6D , the capacitance C _LX0 between the one detection electrode 60L and the weight body 16X is detected with the reference voltage VCOM applied to the other detection electrode 60R. Next, as shown in FIG. _6E , the capacitance C _LXd between the one detection electrode 60L and the weight body 16X is detected with the voltage VDD applied to the other detection electrode 60R. Coulomb force F _CR acting between the other detection electrodes 60R and the weight body 16X plus VDD can be expressed as follows.

Here, the capacity per force due to the Coulomb force is determined from the capacity change due to the applied force F _CL and F _CL (C _RXd −C _RX0 ) and the capacity change due to the applied force F _CR and F _CR (C _LXd −C _LX0 ). The change k _c [F / N] can be expressed as:

When k _c and k _g are equal, if the mass M of the weight is known, the capacitance change due to gravity Mg, that is, the sensitivity of the capacitive acceleration sensor 10X is predicted using k _c as follows. Can do.

  Here, the following formula can be obtained by substituting Formulas 2 and 3 into Formula 5.

A represents the area of the weight, and ρ _Si represents the density of the weight.

  The following relationship exists between the detection capacitor and the gap d between the detection electrode and the weight body.

  By substituting Equation 7 into Equation 6, the following equation can be obtained.

  In the case of Equation 6, the sensitivity is proportional to the square of the gap d between the detection electrode and the weight body, and variation in d becomes an error in prediction sensitivity. On the other hand, in Expression 8, the sensitivity is proportional to the square of the thickness t of the weight body, and the variation in t becomes an error in the predicted sensitivity. Sensitivity is predicted using Equation 6 or Equation 8 according to the cause of variation, and a sensitivity correction value is obtained.

Note that when the sensitivity is predicted using Equation 8, the capacitances C _LX0 and C _RX0 include a parasitic capacitance C _p irrelevant to the Coulomb force, which is one of the error factors. Therefore, the error can be reduced by _obtaining C _p by simulation and using the value obtained by removing C _p from the measured C _LX0 and C _RX0 when obtaining the Coulomb force. _{Alternatively} , the Coulomb forces corresponding to the values of C _LX0 and C _RX0 may be obtained directly from the simulation.

  Further, even if the shape of the capacitive acceleration sensor 10X is formed with a typcal value, and there is no variation in the thickness t and the gap d of the weight body, the sensitivity obtained from the gravity and the sensitivity obtained from the Coulomb force are: There is an error. One reason is that gravity is also applied to the weight body and the beam member that acts as a spring coupled to the weight body, but the Coulomb force is applied only between the detection electrode and the weight body. As for this error, a correction coefficient is calculated by calculating a difference between the sensitivity obtained from the Coulomb force and the sensitivity obtained from gravity, thereby reducing the error in the prediction sensitivity.

  The sensitivity adjustment method for the comb-teeth capacitive acceleration sensor 10Y for detecting the acceleration in the Y-axis direction is the same.

  7 (a) to 7 (e) illustrate a sensitivity adjustment method of a capacitive acceleration sensor for detecting the Z-axis direction used in a capacitive acceleration detecting device having a calibration function according to the present invention. It is a principle figure for doing. Here, a sensitivity adjustment method of the seesaw type capacitive acceleration sensor 20Z will be described.

First, FIG. 7A shows a normal acceleration detection state in which a capacitance change due to gravitational acceleration is detected. The weight body 26Z rotates around the fixed anchor 21 by the torque MgR due to gravity applied to the weight body 26Z having the mass M and the center of gravity at a distance R from the fixed anchor 21. As a result, the capacitance between the detection electrode and the weight body 26Z changes. From the torque MgR and the capacity change resulting from the torque MgR, the capacity change k _Tg [F / (N · m)] per torque can be expressed as follows.

Here, C _LZ is the capacitance between the left detection electrode 23L (corresponding to the detection electrode 23 in FIG. 2) and the weight body 26Z, and C _RZ is the weight of the right detection electrode 24R (corresponding to the detection electrode 24 in FIG. 2). This represents the capacity between the weights 26Z.

On the other hand, the capacity change k _Tg [F / (N · m)] per torque can be obtained by using Coulomb force instead of gravity. This will be described with reference to FIGS. 7B to 7E. First, as shown in FIG. 7B, the capacitance C _LZ0 between the left detection electrode 23L and the weight body 26Z is detected with the reference voltage VCOM applied to the right detection electrode 24R. Next, as shown in FIG. 7C, the capacitance C _LZd between the left detection electrode 23L and the weight body 26Z is detected with the voltage VDD applied to the right detection electrode 24R. The torque T _CL due to the Coulomb force acting between the right detection electrode 24R to which VDD is added and the weight body 26Z can be expressed as follows.

L ₁ represents the distance from the center of the fixed anchor 21 to the end of the electrode on the side of the fixed anchor, L ₂ represents the distance from the center of the fixed anchor 21 to the other end of the fixed electrode, and W _E represents the electrode. Represents the width of.

Next, as shown in FIG. 7D, the capacitance C _RZ0 between the right detection electrode 24R and the weight body 26Z is detected in a state where the reference voltage VCOM is applied to the left detection electrode 23L. Further, as shown in FIG. 7E, the capacitance C _RZd between the right detection electrode 24R and the weight body 26Z is detected with the voltage VDD applied to the left detection electrode 23L. The torque T _CR due to the Coulomb force acting between the left detection electrode 23L to which VDD is added and the weight body 26Z can be expressed as follows.

Here, the capacity change per torque k _Tc from the capacity change due to the applied torque T _CL and T _CL (C _RXd −C _RX0 ) and the capacity change due to the applied torque T _CR and T _CR (C _LXd −C _LX0 ). [F / (N · m)] can be obtained from the following equation.

If k _Tc is equal to k _Tg , and the mass M of the weight is known, the capacitance change due to the torque MgR due to gravity, that is, the sensitivity of the capacitive acceleration sensor should be predicted using k _Tc as follows: Can do.

  By substituting Equations 10 and 11 into Equation 13, the following equation can be obtained.

A represents the area of the weight body, and ρ _Si represents the density of the weight body.

  Further, when the weights of the weights of the capacitive acceleration sensors 10X and 10Y and the capacitive acceleration sensor 20Z are equal, t is obtained from the relationship of Equation 7 and is substituted into Equation 14 to obtain the following equation: Obtainable.

  In the case of Formula 14, the sensitivity formula is proportional to the thickness t of the weight body, and variation in t becomes a sensitivity error. On the other hand, in the case of Expression 15, the sensitivity is proportional to the gap d between the detection electrodes of the capacitive acceleration sensors 10X and 10Y and the weight body, and the variation in d becomes an error in the predicted sensitivity. Sensitivity is predicted using Formula 14 or 15 according to the variation factor, and a sensitivity correction value is obtained.

Note that when the sensitivity is predicted using Equation 14 or 15, the capacitances C _LZ0 and C _RZ0 include a parasitic capacitance C _p irrelevant to the Coulomb force, which is one of the error factors. Therefore, the error can be reduced by _obtaining C _p by simulation and using the value obtained by removing C _p from the measured C _LZ0 and C _RZ0 when obtaining the Coulomb force. _{Alternatively} , the Coulomb force corresponding to the values of C _LZ0 and C _RZ0 may be obtained directly from the simulation.

  Further, the shape of the capacitive acceleration sensors 10X and 10Y is formed by a typcal value, and even when there is no variation in the thickness t and the gap d of the weight body, the sensitivity obtained from the gravity and the sensitivity obtained from the Coulomb force are obtained. There is an error. One reason is that gravity is also applied to the weight body and the beam member that acts as a spring coupled to the weight body, but the Coulomb force is applied only between the detection electrode and the weight body. As for this error, a correction coefficient is calculated by calculating a difference between the sensitivity obtained from the Coulomb force and the sensitivity obtained from gravity, thereby reducing the error in the prediction sensitivity.

  As shown in FIG. 3, when the sensitivity prediction is performed using the mathematical expression 6 in the capacitive acceleration sensors 10X and 10Y, the mathematical expression 15 is used in the capacitive acceleration sensor 20Z. Alternatively, when the sensitivity prediction is performed using the mathematical expression 8 in the capacitive acceleration sensors 10X and 10Y, the mathematical expression 14 is used in the capacitive acceleration sensor 20Z. Thereby, the error factor becomes the same between the capacitive acceleration sensors 10X, 10Y and 20Z, and the relative error of the prediction sensitivity can be reduced.

  Next, a method for predicting the thickness t of the weight body by measuring the capacitance of a plurality of capacitive acceleration sensors and improving the prediction accuracy of sensitivity correction will be described.

Even if lot-to-lot and wafer-to-wafer variations are included, the variation in weight thickness t is considered to be small when a single wafer is considered. Capacitance measurement was performed on the plurality of capacitive acceleration sensors 10X and 10Y on the wafer to obtain a distribution of capacitance values as shown in FIG. The distribution of the appearing capacitance is considered to be caused mainly by the variation in the gap d between the detection electrode and the weight body, and the mode value of the capacitance is considered as the capacitance C (d _typ ) at the typical value d _typ of the gap d. It is done.
On the other hand, there is the following relationship between C (d _typ ) and d _typ .

  From Equation 16, the thickness t of the weight body formed on the wafer can be obtained. Further, instead of such a simple expression, the relationship between C and t can be obtained from simulation, and the accuracy of t can be increased. Thus, t calculated | required can be applied to Numerical formula 8 and Numerical formula 14, and the prediction precision of a sensitivity can be improved. That is, performing sensitivity adjustment means obtaining a sensitivity correction value from a distribution of capacitance values obtained from a plurality of capacitive acceleration sensors.

Under the condition where the process is actually fixed, the distribution representing the relationship between the capacitance change dC _g with respect to gravity and the capacitance change dC (3.3 V) due to the voltage is narrow and close to a straight line. As one of the distribution factors, FIG. 9A shows an example in which the thickness t of the weight body varies and d is substantially constant. FIG. 9B shows an example in which the weight t has a substantially constant thickness t and the gap d varies. In the distributions shown in FIGS. 9A and 9B, the capacitance change with respect to gravity can be obtained on a one-to-one basis from the measurement value of the capacitance change due to the voltage. It can be performed. That is, performing sensitivity adjustment means obtaining a sensitivity correction value from the relationship between the capacitance change with respect to gravity obtained from a plurality of capacitive acceleration sensors and the capacitance change due to voltage.

  FIG. 10 is a flow chart for explaining a calibration method in the capacitance type acceleration detection apparatus having a calibration function according to the present invention. FIGS. 11A to 11O are diagrams illustrating the present invention shown in FIG. It is a specific process figure of the correction method of the sensitivity and offset using the capacitance-type acceleration detection apparatus provided with the calibration function which concerns on this.

  First, the comb-teeth capacitive acceleration sensors 10X and 10Y for detecting X and Y-axis direction accelerations and the seesaw-type electrostatic capacitance for detecting Z-axis direction accelerations included in the capacitive acceleration detecting device 30. The type acceleration sensor 20Z is set in a horizontal state (step S1). Next, the comb-teeth capacitive acceleration sensor 10X for detecting the acceleration in the Y-axis direction is selected by the multiplexer 401 (step S2).

Next, one detection electrode of the selected capacitive acceleration sensor 10X is connected to the capacitive voltage converter 403 via the multiplexer 401, and the other detection electrode is connected to the reference voltage VCOM via the multiplexer 401. The capacitance C _LXO between one detection electrode and the weight body is measured (step S3; FIG. 11A).

Next, the other detection electrode connected to the reference voltage VCOM is connected to the voltage VDD via the multiplexer 401, and one detection electrode is connected to the electrode capacitance voltage converter 403 via the multiplexer 401. The capacitance C _LXd between the weight bodies is measured (step S4; FIG. 11B).

Next, one detection electrode connected to the electrode capacitance voltage converter 403 is connected to the reference voltage VCOM via the multiplexer 401, and the other detection electrode is connected to the electrode capacitance voltage converter 403 via the multiplexer 401. Then, the capacitance C _RXO between the other detection electrode and the weight body is measured (step S5; FIG. 11C).

Next, one detection electrode connected to the reference voltage VCOM is connected to the voltage VDD via the multiplexer 401, the other detection electrode is connected to the electrode capacitance voltage converter 403 via the multiplexer 401, and the other detection electrode is connected. The capacitance C _RXd between the electrode and the weight body is measured (step S6; FIG. 11D).

Next, it is determined whether or not the measured capacity is within a certain threshold (step S7), and if it is not within the threshold, it is disposed as a defective product. That is, a non-defective product / defective product is determined based on whether or not the obtained capacitances C _LX0 , C _LXd , C _LY0 , C _LYd , C _LZ0 , C _LZd are within a certain threshold.

  Next, if it is within the threshold value, it is determined whether or not the capacitance measurement has been completed for all the sensors of the X, Y, and Z axes (step S8), and if not completed, the process returns to step S2, and the processing after step 3 is performed. repeat. That is, steps S3 to S7 are repeated for the comb-tooth capacitive acceleration sensor 10Y for detecting the Y-axis direction acceleration and the seesaw-type capacitive acceleration sensor 20Z for detecting the Z-axis direction acceleration (FIG. 11E to 11L).

Next, when all the capacitance measurements are completed, the parasitic capacitance is removed from the measured capacitance (step S9). That is, the parasitic capacitance is removed from the obtained capacitances C _LX0 , C _LXd , C _LY0 , C _LYd , C _LZ0 , and C _LZd .

  Next, the sensitivity of the X, Y, and Z-axis sensors is obtained from the capacitance from which the parasitic capacitance has been removed using Equation 8 and Equation 14 (step S10). Next, the error is corrected with a correction value resulting from the difference between gravity and Coulomb force (step S11). Next, a sensitivity correction value is obtained based on the obtained sensitivity, and the variable gain amplifier 404 is adjusted (step S12).

Next, again, the comb-teeth capacitive acceleration sensor 10X for X-axis direction acceleration detection is selected by the multiplexer 401 (step S13). Next, a pair of detection electrodes are connected to the capacitance-voltage converter 403, and the capacitance between one detection electrode and the weight body and the capacitance difference (C _LXO −C _RXO ) between the other detection electrode and the weight body are _calculated . Measurement is performed (step S14; FIG. 11M).

  Next, an offset is obtained from the measured capacity difference (step S15). Next, it is determined whether or not the capacitance measurement has been completed for all the sensors of the X, Y, and Z axes (step S16). If not completed, the process returns to step S13 and the processes of steps 14 and 15 are repeated. That is, steps S14 and 15 are repeated for the comb-tooth capacitive acceleration sensor 10Y for Y-axis direction acceleration detection and the seesaw-type capacitive acceleration sensor 20Z for Z-axis direction acceleration detection (FIG. 11N). And FIG.

  Next, the offset correction circuit 406 is adjusted based on the obtained capacitance difference (step S17). Next, the obtained sensitivity correction value and offset correction value are stored in the EEPROM 410 (step S18).

  After performing such calibration, the capacitive acceleration detection device of the present invention measures the capacitance difference between the two detection electrodes in the state of the multiplexer 401 as shown in FIGS. , Acceleration detection in the Z-axis direction can be performed.

  FIGS. 12A to 12C are configuration diagrams for explaining another embodiment of the capacitive acceleration sensor according to the present invention. FIG. 12A is a top view, and FIG. 12A is a cross-sectional view taken along the line AA ′ in FIG. 12A, and FIG. 12C is a cross-sectional view taken along the line BB ′ in FIG.

  This capacitive acceleration sensor includes a comb-shaped capacitive acceleration sensor 10X arranged for the X-axis shown in FIG. 3 and a comb-shaped capacitive acceleration sensor 10Y arranged for the Y-axis. Are combined to realize a comb-teeth capacitive acceleration sensor 120 that also serves as an XY axis. That is, this means that the weight body of the comb-shaped X-axis capacitive acceleration sensor and the weight body of the comb-shaped Y-axis capacitive acceleration sensor are the same.

  Accordingly, the capacitance type acceleration detection device of the present invention in this case includes a comb-type capacitance type acceleration sensor 120 that also serves as an XY axis, and a seesaw type capacitance type acceleration sensor 20Z arranged for the Z axis. Is an electrostatic capacitance type three-axis acceleration sensor integrally configured.

  As described above, this capacitive acceleration sensor is a comb-shaped capacitive acceleration sensor 120, which is a displaceable weight body 129 and a comb-tooth movable electrode 127 a coupled to the weight body 129. 127d, comb-tooth movable electrodes 128a to 128d, fixed electrodes 123a to 123d, fixed electrodes 124a to 124d arranged opposite to each other with the comb-tooth movable electrodes 127a to 127d interposed therebetween, and comb-tooth movable electrodes 128a to 128d sandwiched therebetween. The fixed electrodes 125a to 125d, the fixed electrodes 126a to 126d, the beam members 122a to 122d coupled to the weight body 129, the fixed anchor 121a coupled to the beam member 122a, and the beam member 122b are disposed to face each other. Fixed anchor 121b, fixed anchor 121c coupled to beam member 122c, and coupled to beam member 122d A fixed anchor 121d and a substrate 130 that supports the fixed anchors 121a to 121d are provided. When detecting acceleration in the X-axis direction, the comb-tooth movable electrodes 128a to 128d and one of the detection electrodes (fixed electrodes 125a to 125d) When detecting the change in capacitance between the movable electrode 128a to 128d and the other detection electrode (fixed electrode 126a to 126d) and detecting the acceleration in the Y-axis direction, Change in capacitance between the movable electrodes 127a and 127d and one of the detection electrodes (fixed electrodes 123a and 123d), and electrostatic between the movable electrodes 127a and 127d and the other detection electrodes (fixed electrodes 124a and 124d) It is configured to detect a change in capacitance.

  The capacitive acceleration sensor 10X arranged for the X axis and the capacitive acceleration sensor 10Y arranged for the Y axis shown in FIG. 3 may be replaced with the XY axis acceleration sensor shown in FIG. Obviously, it is possible to realize a capacitance-type acceleration detecting apparatus having a calibration function for adjusting sensitivity and adjusting offset as shown in FIG.

10 Comb-type capacitive acceleration sensor 10X X-axis comb-type capacitive acceleration sensor 10Y Y-axis comb-type capacitive acceleration sensor 11a, 11b Fixed anchor 12a and 12d Beam member 13a From 13f, 14a to 14f Fixed electrode 15 Substrate 16, 26 Weight body 16X, 16Y, 26X Weight body 17a to 17f Comb movable electrode 20 Seesaw type capacitive acceleration sensor 20Z Z-axis seesaw type electrostatic Capacitive acceleration sensor 21 Fixed anchor 22a to 22b Beam member 23 Left detection fixed electrode 24 Right detection fixed electrode 25 Substrate 30 Capacitance type three-axis acceleration sensors 51a, 51b Single-end capacitance voltage conversion circuit 52 Differential amplification circuit 53 Selector 60L One detection electrode 60R The other detection electrode 120 Comb-type capacitive acceleration sensors 121a, 12 b, 121c, 121d Fixed anchor 122a to 122d Beam member 123a to 123d, 124a to 124d, 125a to 125d, 126a to 126d Fixed electrode 127a to 127d, 128a to 128d Comb tooth movable electrode 129 Weight body 130 Substrate 401 Multiplexer 402 Voltage Source 403 Capacitance voltage conversion circuit 404 Variable gain amplifier 405 Demodulation circuit 406 Offset correction circuit 407 Analog to digital converter 408 Digital interface 409 Oscillation circuit 410 EEPROM

Claims (14)

A displaceable weight body and a weight body provided opposite to the weight body, and the capacitance between one detection electrode and the weight body increases due to the displacement of the weight body, and the other detection electrode and the weight body In a capacitance type acceleration detection device that has a capacitance type acceleration sensor having a plurality of pairs of detection electrodes whose capacitance with the body decreases and adjusts sensitivity and offset,
Electrode selection means for selecting a pair of detection electrodes from the plurality of pairs of detection electrodes provided in the capacitive acceleration sensor;
Capacitance detection means for detecting a capacitance between the one detection electrode and the other detection electrode of the pair of detection electrodes selected by the electrode selection means and the weight body;
Voltage application means for applying a voltage to the one detection electrode and the other detection electrode of the pair of detection electrodes selected by the electrode selection means;
Storage means for holding a sensitivity correction value and an offset correction value obtained from the capacitance detected by the capacitance detection means and the voltage applied to the detection electrode;
Sensitivity adjustment means for performing sensitivity adjustment according to the correction value held by the storage means;
An electrostatic capacity type acceleration detecting apparatus, comprising: an offset adjusting unit that performs an offset adjustment with a correction value held by the storage unit.   2. The capacitive acceleration detection device according to claim 1, wherein the capacitive acceleration sensor includes a plurality of capacitive acceleration sensors having the same thickness of the weight body.   The capacitive acceleration detection apparatus according to claim 1, wherein the voltage application unit includes a voltage generation source, and applies a voltage generated by the voltage generation source to the detection electrode.   4. The capacitive acceleration detecting device according to claim 1, wherein the voltage applying unit applies an externally supplied voltage to the detection electrode.   Capacitance detection means has a function of converting a capacitance between the one detection electrode and the weight body of the selected pair of detection electrodes into a voltage, and a capacitance between the other detection electrode and the weight body. And a function of converting the difference between the capacitance between the one detection electrode and the weight body and the capacitance between the other detection electrode and the weight body into a voltage. The capacitance-type acceleration detection apparatus according to claim 1, wherein:   Capacitance detecting means for detecting two capacities individually, a single-end capacitance-voltage conversion circuit, a differential amplifier circuit for outputting a difference between output voltages from the single-end capacitance-voltage conversion circuit, and the single-end capacitance-voltage conversion circuit 6. A capacitive acceleration detecting device according to claim 1, wherein the selector selects one output from an output from the differential amplifier and an output from the differential amplifier circuit. .   7. The capacitance type acceleration detection apparatus according to claim 1, wherein a parasitic capacitance removing unit is added to the sensitivity adjusting unit.   The capacitive acceleration sensor includes a comb-shaped X-axis capacitive acceleration sensor, a comb-shaped Y-axis capacitive acceleration sensor, and a seesaw-type Z-axis capacitive acceleration sensor. 8. The capacitive acceleration detecting device according to claim 1, wherein the capacitive acceleration detecting device is a capacitive three-axis acceleration sensor integrally formed with the sensor.   9. The weight body of the comb-shaped X-axis capacitive acceleration sensor and the weight body of the comb-shaped Y-axis capacitive acceleration sensor are the same. The capacitance-type acceleration detection apparatus as described. A displaceable weight body and a weight body provided opposite to the weight body, and the capacitance between one detection electrode and the weight body increases due to the displacement of the weight body, and the other detection electrode and the weight body Calibration that adjusts sensitivity and offset in a capacitive acceleration sensor that has a capacitance-type acceleration sensor that includes a plurality of pairs of detection electrodes that reduce the capacitance with the body, and detects the difference between the pair of capacitances In the method
Applying a reference voltage to one detection electrode facing the weight body to detect a capacitance between the other detection electrode and the weight body;
Applying a voltage different from the reference voltage to the one detection electrode to detect a capacitance between the other detection electrode and the weight body;
Obtaining a sensitivity correction value from the detected capacitance and performing sensitivity adjustment;
Detecting a capacitance difference between the detected capacitance between the one detection electrode and the weight body and the detected capacitance between the other detection electrode and the weight body;
A calibration method for a capacitive acceleration detecting apparatus, comprising: calculating an offset correction value from the detected capacitance difference and performing offset correction.   The calibration method for the electrostatic capacitive acceleration detecting apparatus according to claim 10, wherein the step of adjusting sensitivity obtains a sensitivity correction value by removing parasitic capacitance from the detected capacitance.   The electrostatic sensitivity according to claim 10 or 11, wherein the step of adjusting the sensitivity uses a value obtained by multiplying the sensitivity correction value by a difference between gravity and Coulomb force as a coefficient as the sensitivity correction value. Calibration method in capacitive acceleration detection apparatus.   13. The electrostatic capacitance according to claim 10, 11 or 12, wherein the step of adjusting the sensitivity obtains the sensitivity correction value from a distribution of capacitance values obtained from a plurality of capacitive acceleration sensors. Calibration method in a type acceleration detection apparatus.   12. The sensitivity correction value is obtained from a relationship between a change in capacitance with respect to gravity obtained from a plurality of capacitive acceleration sensors and a change in capacitance due to voltage in the step of performing sensitivity adjustment. Or a calibration method in the electrostatic capacitive acceleration detecting device according to 12.

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