Capacitance measurement circuit and load detection device

Abstract

The present disclosure addresses the problem of providing a capacitance measurement circuit capable of improving capacitance measurement accuracy. A capacitance measurement circuit (A1) comprises a plurality of detection circuits (20), a switching circuit (30), and a control circuit (10). Each of the detection circuits (20) includes a power supply unit (1), a potential generation unit (3), and a detection unit (2). The potential generation unit (3) outputs, to a part to be measured, a potential for making two electrodes of the part to be measured have the same potential. The detection unit (2) detects a voltage corresponding to the capacitance of the part to be measured. The switching circuit (30) includes a switching unit (33). On the basis of control from the control circuit (10), the switching unit (33) changes the two electrodes of the part to be measured to have one of the same potential and different potentials. The control circuit (10) calculates the capacitance of the part to be measured on the basis of the difference between a first capacitance corresponding to the voltage detected by the detection unit (2) when the two electrodes of the part to be measured have different potentials, and a second capacitance corresponding to the voltage detected by the detection unit (2) when the two electrodes of the part to be measured have the same potential.

Description

Capacitance measurement circuit and load detection device 【0001】 The present disclosure generally relates to a capacitance measurement circuit and a load detection device, and more particularly to a capacitance measurement circuit that measures capacitance and a load detection device that detects a load based on the measurement result of the capacitance. 【0002】 An example of the capacitance measurement circuit described in Patent Document 1 is illustrated. The capacitance measurement circuit measures the capacitance of the element portion based on the change in voltage when a voltage is applied to the element portion of the load sensor. The capacitance measurement circuit includes a control unit, a plurality of switch elements, a measurement unit, an equipotential generation unit, and a plurality of element selection units. 【0003】 In the capacitance measurement circuit described in Patent Document 1, there may be cases where it is desired to further improve the measurement accuracy of the capacitance. 【0004】 International Publication No. 2024 / 105923 【0005】 An object of the present disclosure is to provide a capacitance measurement circuit and a load detection device capable of further improving the measurement accuracy of capacitance. 【0006】A capacitance measuring circuit according to one aspect of the present disclosure comprises a plurality of detection circuits, a switching circuit, and a control circuit. The plurality of detection circuits are electrically connected to one or more capacitance units among the plurality of capacitance units. The switching circuit switches the connection state between the plurality of capacitance units and the plurality of detection circuits. The control circuit controls the plurality of detection circuits and the switching circuit. Each of the plurality of detection circuits has a power supply unit, a potential generation unit, and a detection unit. The power supply unit supplies a voltage to the unit to be measured, which is the capacitance unit to be measured among the plurality of capacitance units. The potential generation unit generates a potential to set the first electrode and the second electrode of the unit to be measured to the same potential, and outputs the generated potential to the unit to be measured via the switching circuit. The detection unit detects a voltage corresponding to the capacitance of the unit to be measured. The switching circuit has a switching unit. Based on control from the control circuit, the switching unit switches the first electrode and the second electrode of the unit to be measured to either the same potential or different potentials. The control circuit calculates the capacitance of the part under test by the difference between a first capacitance corresponding to the voltage detected by the detection unit when the first and second electrodes of the part under test are at different potentials, and a second capacitance corresponding to the voltage detected by the detection unit when the first and second electrodes of the part under test are at the same potential. 【0007】 A load detection device according to one aspect of the present disclosure comprises a capacitance measuring circuit and a load sensor. The load sensor has a plurality of capacitance sections. The load sensor further comprises a plurality of first conductors and a second conductor. The plurality of first conductors are arranged in a line in one direction and are electrically connected one-to-one with the plurality of detection circuits. The second conductors are arranged to intersect with the plurality of first conductors and are electrically connected with the switching circuit. Each of the plurality of capacitance sections is interposed at the intersection of the plurality of first conductors and the second conductors. 【0008】Figure 1 is a circuit diagram of a load detection device equipped with a capacitance measurement circuit according to Embodiment 1. Figure 2 is an explanatory diagram illustrating the operation of the load detection device. Figure 3 is a circuit diagram of a load detection device equipped with a capacitance measurement circuit according to a comparative example. Figure 4 is a graph showing the relationship between the capacitance of the part to be measured and the detection voltage of the detection unit, relating to the load detection device equipped with a capacitance measurement circuit according to Embodiment 1. Figure 5 is a perspective view of the load sensor in the load detection device with the second base member removed. Figure 6 is a perspective view of the load sensor in the load detection device. Figure 7 is a cross-sectional view of the load sensor in the load detection device with no load applied. Figure 8 is a cross-sectional view of the load sensor in the load detection device with a load applied. Figure 9 is a circuit diagram of a load detection device equipped with a capacitance measurement circuit according to Embodiment 2. 【0009】 The load detection device equipped with a capacitance measurement circuit according to Embodiments 1 and 2 will be described below with reference to the drawings. The figures described in each embodiment below are schematic diagrams, and the ratios of the size and thickness of each component do not necessarily reflect the actual dimensional ratios. Furthermore, the configurations described in each embodiment below are merely examples of this disclosure. This disclosure is not limited to the embodiments below, and various modifications are possible depending on the design, etc., as long as the effects of this disclosure can be achieved. Furthermore, this disclosure can also be applied by appropriately combining at least some of the configurations of each embodiment below. 【0010】 (Embodiment 1) Hereinafter, a load detection device B1 equipped with a capacitance measurement circuit A1 according to Embodiment 1 will be described with reference to Figures 1 to 8. Figures 7 and 8 are cross-sectional views taken along the line X-X in Figure 6. Furthermore, the capacitance measurement circuit A1 will be described first, followed by the load detection device B1. 【0011】(1) Capacitance Measurement Circuit The capacitance measurement circuit A1 shown in Figure 1 measures the capacitance of the capacitance part to be measured. For example, the capacitance measurement circuit A1 measures the capacitance of each of the multiple (nine in the example in Figure 1) capacitance parts 41 to 49 in the load sensor 50. In this embodiment, the multiple capacitance parts 41 to 49 are arranged in a matrix (a 3x3 matrix in the example in Figure 1). 【0012】 The capacitance measurement circuit A1 comprises a plurality of detection circuits 20 (three in the example shown in Figure 1), a switching circuit 30, and a control circuit 10. The plurality of detection circuits 20 include a first detection circuit 21, a second detection circuit 22, and a third detection circuit 23. 【0013】 (2) Components of the capacitance measurement circuit (2.1) Detection circuit Each of the multiple detection circuits 20 is electrically connected to one or more of the multiple capacitance units 41 to 49 (three in the example of Figure 1). Specifically, the first detection circuit 21 is electrically connected to three capacitance units 41, 44, and 47 via a connecting line 7 and a first conductor 5 (see Figures 1 and 5). The second detection circuit 22 is electrically connected to three capacitance units 42, 45, and 48 via a connecting line 7 and a first conductor 5. The third detection circuit 23 is electrically connected to three capacitance units 43, 46, and 49 via a connecting line 7 and a first conductor 5. 【0014】 Since the configurations of the multiple detection circuits 20 are the same, unless otherwise specified, the following description will focus on one detection circuit 20. 【0015】 The detection circuit 20 includes a power supply unit 1, a detection unit 2, and a potential generation unit 3. 【0016】 The power supply unit (first voltage output unit) 1 supplies voltage to the capacitance unit to be measured based on control from the control circuit 10. For example, when measuring the capacitance of the capacitance unit 41 of the first detection circuit 21, the power supply unit 1 supplies voltage to the capacitance unit 41 based on control from the control circuit 10. In the following, the capacitance unit to be measured may also be referred to as the "unit under measurement". 【0017】As shown in Figure 2, the power supply unit 1 includes a power supply V1, a first switching element 1a, a second switching element 1b, a third switching element 1c, and a capacitor 4. 【0018】 Power supply V1 is configured to output a predetermined voltage. 【0019】 Each of the first switching element 1a and the second switching element 1b is, for example, a p-channel MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor). The p-channel MOSFET is, for example, a normally-on Si-based MOSFET. The third switching element 1c is, for example, an n-channel MOSFET. The n-channel MOSFET is, for example, a normally-off Si-based MOSFET. 【0020】 Each of the first switch element 1a, the second switch element 1b, and the third switch element 1c has a first main terminal, a second main terminal, and a control terminal. In the following description to aid in understanding the embodiment, the first main terminal will be referred to as the "drain terminal," the second main terminal as the "source terminal," and the control terminal as the "gate terminal." 【0021】 The drain terminal of the first switch element 1a is electrically connected to the power supply V1. The gate terminal of the first switch element 1a is electrically connected to the control circuit 10. The source terminal of the first switch element 1a is electrically connected to the drain terminal of the second switch element 1b. In addition, the source terminal of the first switch element 1a is electrically connected to ground (circuit ground) via the capacitor 4. 【0022】 The gate terminal of the second switch element 1b is electrically connected to the control circuit 10. The source terminal of the second switch element 1b is electrically connected to the drain terminal of the third switch element 1c. The gate terminal of the third switch element 1c is electrically connected to the control circuit 10. The source terminal of the third switch element 1c is electrically connected to ground. 【0023】The detection unit 2 detects a voltage corresponding to the capacitance of the unit under measurement (in the example in Figure 2, the capacitance unit 41). The detection unit 2 also outputs the detected voltage (detected voltage) to the control circuit 10. The detection unit 2 is, for example, an ADC (Analog to Digital Converter). 【0024】 The detection unit 2 is electrically connected in parallel with the unit being measured. Furthermore, the detection unit 2 is electrically connected in parallel with the third switch element 1c. More specifically, the detection unit 2 is electrically connected between the drain terminal and the source terminal of the third switch element 1c. 【0025】 The potential generation unit (first potential output unit) 3 shown in Figure 1 generates a potential to bring the first electrode and second electrode (hereinafter referred to as "both electrodes") of the unit to be measured to the same potential (the same potential as each other), and outputs the generated potential to the unit to be measured via the switching circuit 30. In other words, the potential generation unit 3 has the function of making the potential of the connecting wire 7 and the potential of the connecting wire 8 the same potential. The potential generation unit 3 is, for example, a VF (Voltage Follower). The potential generation unit 3 is electrically connected to the power supply unit 1 and the detection unit 2. The potential generation unit 3 is also electrically connected to the switching circuit 30. Note that in Figure 2, the illustration of the potential generation unit 3 is omitted for the sake of explanation. Also, in Figure 2, the illustration of the switch circuits 31 and 32, which will be described later, is omitted for the sake of explanation. 【0026】 (2.2) Switching Circuit The switching circuit 30 shown in Figure 1 is configured to switch the connection state between the multiple capacitance units 41 to 49 and the multiple detection circuits 20. 【0027】 The switching circuit 30 includes a switch circuit 31, a switch circuit 32, and a plurality of switches 33 to 35 (three in the example shown in Figure 1). 【0028】 The switch circuit 31 is an SP3T (Single Pole 3 Throws) analog switch. The switch circuit 31 has a first input terminal, a second input terminal, a third input terminal, and an output terminal. 【0029】The first input terminal of the switch circuit 31 is electrically connected to the first detection circuit 21 (specifically, the potential generation unit 3 of the first detection circuit 21). The second input terminal of the switch circuit 31 is electrically connected to the second detection circuit 22 (specifically, the potential generation unit 3 of the second detection circuit 22). The third input terminal of the switch circuit 31 is electrically connected to the third detection circuit 23 (specifically, the potential generation unit 3 of the third detection circuit 23). The output terminal of the switch circuit 31 is electrically connected to the switch circuit 32. 【0030】 The switch circuit 31 switches the connection state between the multiple detection circuits 20 and the switch circuit 32 based on control from the control circuit 10. 【0031】 The switch circuit 32 is, for example, a DPDT (Double Poles Double Throws) analog switch. The switch circuit 32 has a first input terminal, a second input terminal, a third input terminal, a fourth input terminal, a first output terminal, and a second output terminal. 【0032】 The first and fourth input terminals of switch circuit 32 are electrically connected to ground. The second and third input terminals of switch circuit 32 are electrically connected to the output terminals of switch circuit 31. The first and second output terminals of switch circuit 32 are electrically connected to the multiple switches 33 to 35. 【0033】 The switch circuit 32 switches the connection state between the switch circuit 31 and the plurality of switches 33 to 35 based on control from the control circuit 10. In this embodiment, the switch circuit 32 is selected so that the first input terminal and the first output terminal are in a conductive state, and the third input terminal and the second output terminal are in a conductive state. 【0034】Switch 33 is an SP2T (Single Pole 2 Throws) analog switch. Switch 33 has a first input terminal, a second input terminal, and an output terminal. The first input terminal of switch 33 is electrically connected to the first output terminal of switch circuit 32. The second input terminal of switch 33 is electrically connected to the second output terminal of switch circuit 32. The output terminal of switch 33 is electrically connected to a plurality (three in the example of Figure 1) of capacitance units 41-43 via a connecting wire 8 and a second conductor 6 (see Figures 1 and 5). 【0035】 Based on control from the control circuit 10, switch 33 switches the connection state between the switch circuit 32 and the three capacitance units 41-43. In other words, switch 33 switches the connection state between the three detection circuits 20 and the three capacitance units 41-43. Also, based on control from the control circuit 10, switch 33 switches both electrodes of the unit to be measured (for example, the capacitance unit 41) to either the same potential or different potentials (potentials that are different from each other). 【0036】 Switch 34 is an SP2T (Single Pole 2 Throws) analog switch. Switch 34 has a first input terminal, a second input terminal, and an output terminal. The first input terminal of switch 34 is electrically connected to the first output terminal of switch circuit 32. The second input terminal of switch 34 is electrically connected to the second output terminal of switch circuit 32. The output terminal of switch 34 is electrically connected to a plurality (three in the example of Figure 1) of capacitance units 44-46 via a connecting wire 8 and a second conductor 6. 【0037】 Based on control from the control circuit 10, switch 34 switches the connection state between the switch circuit 32 and the three capacitance units 44-46. In other words, switch 34 switches the connection state between the three detection circuits 20 and the three capacitance units 44-46. Also, based on control from the control circuit 10, switch 34 switches both electrodes of the unit to be measured (for example, the capacitance unit 44) to either the same potential or different potentials. 【0038】Switch 35 is an SP2T (Single Pole 2 Throws) analog switch. Switch 35 has a first input terminal, a second input terminal, and an output terminal. The first input terminal of switch 35 is electrically connected to the first output terminal of switch circuit 32. The second input terminal of switch 35 is electrically connected to the second output terminal of switch circuit 32. The output terminal of switch 35 is electrically connected to a plurality (three in the example of Figure 1) of capacitance units 47-49 via a connecting wire 8 and a second conductor 6. 【0039】 Based on control from the control circuit 10, switch 35 switches the connection state between the switch circuit 32 and the three capacitance units 47-49. In other words, switch 35 switches the connection state between the three detection circuits 20 and the three capacitance units 47-49. Also, based on control from the control circuit 10, switch 35 switches both electrodes of the unit to be measured (for example, the capacitance unit 47) to either the same potential or different potentials. 【0040】 (2.3) Control circuit The control circuit 10 controls a plurality of detection circuits 20 and switching circuits 30. 【0041】 The control circuit 10 is implemented, for example, by a computer system having one or more processors and one or more memories, or by an FPGA (Field Programmable Gate Array). In other words, the functions of the control circuit 10 are realized by one or more processors executing a program stored in memory. The program may be pre-stored in memory, provided via a telecommunication line such as the Internet, or provided on a non-temporary recording medium such as a memory card. 【0042】 The control circuit 10 is electrically connected to multiple detection circuits 20. The control circuit 10 is also electrically connected to a switching circuit 30. More specifically, the control circuit 10 is electrically connected to a switch circuit 31, a switch circuit 32, and multiple switches 33-35. 【0043】The control circuit 10 controls the plurality of detection circuits 20 and the switching circuit 30 so as to acquire one by one the voltages corresponding to the capacitance of the measurement target part from among the plurality of capacitance parts 41 to 49. Further, the control circuit 10 calculates the capacitance of the measurement target part based on the voltage change of the measurement target part when a voltage is supplied to the measurement target part. Note that the voltage change of the measurement target part is assumed to be, for example, a voltage change caused by the load P1 (see FIG. 8). 【0044】 Further, when both electrodes of the measurement target part are at different potentials, the control circuit 10 calculates the capacitance of the measurement target part by the difference between the capacitance (first capacitance) corresponding to the voltage detected by the detection part 2 of the detection circuit 20 and the capacitance (second capacitance) corresponding to the voltage detected by the detection part 2 when both electrodes of the measurement target part are at the same potential. 【0045】 (3) Operation of the capacitance measurement circuit Next, the operation of the capacitance measurement circuit A1 will be described based on FIG. 2. Hereinafter, for the sake of convenience of explanation, the case of measuring the capacitance of one capacitance part 41 out of the plurality of capacitance parts 41 to 49 will be described. 【0046】 The control circuit 10 controls the switching circuit 30 so that the first detection circuit 21 and the capacitance part 41 are electrically connected. Further, the control circuit 10 controls the switch 33 so that the first electrode and the second electrode of the capacitance part 41 are at different potentials. As a result, both electrodes of the capacitance part 41 are at different potentials. 【0047】 Further, the control circuit 10 controls the switch 34 (see FIG. 1) so that the first electrode and the second electrode of each of the three capacitance parts 44 to 46 (see FIG. 1) are at the same potential. Further, the control circuit 10 controls the switch 35 (see FIG. 1) so that the first electrode and the second electrode of each of the three capacitance parts 47 to 49 (see FIG. 1) are at the same potential. As a result, both electrodes of each of the three capacitance parts 44 to 46 are at the same potential, and both electrodes of each of the three capacitance parts 47 to 49 are at the same potential. Therefore, each of the six capacitance parts 44 to 49 is in a state where it has disappeared circuitously (invalid state). 【0048】Further, the control circuit 10 controls the first detection circuit 21 so as to supply a voltage from the power supply unit 1 to the capacitance unit 41 after both electrodes of the capacitance unit 41 become non-equipotential. 【0049】 Specifically, the control circuit 10 controls the first switch element 1a, the second switch element 1b, and the third switch element 1c so that the first switch element 1a and the third switch element 1c are in the on state and the second switch element 1b is in the off state. As a result, since a predetermined voltage is supplied to the capacitor 4 from the power supply V1, charges are accumulated (charged). 【0050】 When the capacitor 4 is charged (for example, fully charged), the control circuit 10 controls the first switch element 1a so that the first switch element 1a is in the off state. 【0051】 Further, after the first switch element 1a is in the off state, the control circuit 10 controls the third switch element 1c so that the third switch element 1c is in the off state. The period from the time when the first switch element 1a is in the off state to the time when the third switch element 1c is in the off state is set to be not less than a predetermined period. The predetermined period may be, for example, a period during which the charges (remaining charges) remaining in the capacitance unit 41 can be discharged. 【0052】 Note that the control circuit 10 discharges the remaining charges of the capacitance unit 41, but the discharge of the remaining charges of the capacitance unit 41 is not essential. Further, after the first switch element 1a is in the off state, the control circuit 10 controls the first switch element 1a and the third switch element 1c so that the third switch element 1c is in the off state. However, the first switch element 1a and the third switch element 1c may be controlled so that the first switch element 1a and the third switch element 1c are simultaneously in the off state. 【0053】Furthermore, the control circuit 10 controls the second switch element 1b so that it turns ON after the residual charge in the capacitance section 41 has been discharged. As a result, the capacitance section 41 receives charge distribution or transfer from the capacitor 4, and thus accumulates charge (is charged). Charge also accumulates in the parasitic capacitance sections (hereinafter referred to as "first parasitic capacitance sections") present in the circuit between the power supply section 1 and the capacitance section 41, and in other electronic components (for example, the second switch element 1b, the detection section 2, etc.). In short, the capacitance section 41 and the first parasitic capacitance sections are charged. 【0054】 After the capacitance unit 41 and the first parasitic capacitance unit are charged, the control circuit 10 calculates the capacitance of the capacitance unit 41 (first capacitance) based on the detection voltage detected by the detection unit 2. Here, the first capacitance includes the capacitance of the first parasitic capacitance unit (so-called parasitic capacitance). 【0055】 The control circuit 10 calculates the first capacitance of the capacitance unit 41, and then controls the switch 33 so that the first and second electrodes of the capacitance unit 41 are at the same potential. As a result, both electrodes of the capacitance unit 41 are at the same potential. 【0056】 Furthermore, the control circuit 10 controls the first switch element 1a, the second switch element 1b, and the third switch element 1c so that, after both electrodes of the capacitance section 41 reach the same potential, the first switch element 1a and the third switch element 1c are turned ON, and the second switch element 1b is turned OFF. As a result, the capacitor 4 is charged again because a predetermined voltage is supplied from the power supply V1. Also, the stored charge in the capacitance section 41 is discharged. 【0057】The control circuit 10 controls the first switch element 1a so that it turns off once the capacitor 4 is charged. After the first switch element 1a is turned off, the control circuit 10 controls the third switch element 1c so that it turns off. After the third switch element 1c is turned off, the control circuit 10 controls the second switch element 1b so that it turns on. Since both electrodes of the capacitance section 41 are at the same potential (meaning the capacitance section 41 is effectively gone from the circuit), no charge is accumulated in the capacitance section 41, and charge is accumulated in the first parasitic capacitance section. In short, only the first parasitic capacitance section is charged. 【0058】 After the first parasitic capacitance unit is charged, the control circuit 10 calculates the capacitance of the capacitance unit 41 (second capacitance) based on the detection voltage detected by the detection unit 2. 【0059】 The control circuit 10 calculates the capacitance of the capacitance section 41 by the difference between the first capacitance (capacitance of the capacitance section 41 and the first parasitic capacitance section) and the second capacitance (capacitance of the first parasitic capacitance section). In other words, the control circuit 10 calculates the capacitance of the capacitance section 41 by canceling the capacitance of the first parasitic capacitance section. As a result, the capacitance measurement circuit A1 can accurately measure the capacitance of the capacitance section 41, improving the accuracy of capacitance measurement. 【0060】 The following is an example of a comparative capacitance measurement circuit Z1 (see Figure 3). 【0061】 The comparative example capacitance measurement circuit Z1 measures the capacitance of each of the multiple capacitance sections 41 to 49 in the load sensor 50. The comparative example capacitance measurement circuit Z1 includes, for example, one detection circuit 20, a control circuit 10, and two switching circuits 80 and 90. 【0062】The switching circuit 80 switches the connection state between the multiple capacitance units 41-49 and the one detection circuit 20. The switching circuit 80 has a switch circuit 84 and three switches 81-83. The three switches 81-83 have the same function as the three switches 33-35 in the capacitance measurement circuit A1. The switch circuit 84 has the same function as the switch circuit 32 in the capacitance measurement circuit A1. In short, the switching circuit 80 does not have the switch circuit 31 of the switching circuit 30 in the capacitance measurement circuit A1. 【0063】 The switching circuit 90 switches the connection state between the multiple capacitance units 41 to 49 and the one detection circuit 20. The switching circuit 90 has three switches 91 to 93. Each of the three switches 91 to 93 is an analog switch, just like each of the three switches 81 to 83. 【0064】 The control circuit 10 is configured to calculate the capacitance of each of the multiple capacitance units 41 to 49 using one detection circuit 20 and a switching circuit 90. 【0065】 In the comparative example capacitance measurement circuit Z1, for example, when measuring the capacitance of the capacitance section 41, the control circuit 10 controls two switching circuits 80 and 90 and calculates the capacitance of the capacitance section 41 based on the detection voltage detected by one detection circuit 20. 【0066】 In the comparative example capacitance measurement circuit Z1, the control circuit 10 calculates the capacitance of the capacitance unit 41 by canceling the capacitance of parasitic capacitance units (hereinafter referred to as "second parasitic capacitance units") present in the electrical circuit between the power supply unit 1 and the capacitance unit 41 and in other electronic components (for example, the switching circuit 90, etc.). 【0067】By the way, in the comparative example capacitance measurement circuit Z1, when measuring the capacitance of the part to be measured (for example, the capacitance part 41), a switching circuit 90 (specifically, three switches 91 to 93) is provided in the circuit between one detection circuit 20 and the capacitance part 41. As a result, the capacitance of the second parasitic capacitance part becomes larger than the capacitance of the first parasitic capacitance part in the capacitance measurement circuit A1. Consequently, in the comparative example capacitance measurement circuit Z1, for example, when the capacitance of the part to be measured is small, there is a possibility that measurement errors due to the parasitic capacitance part will occur more than in the capacitance measurement circuit A1 of this embodiment. Therefore, the measurement accuracy of the comparative example capacitance measurement circuit Z1 may be lower than that of the capacitance measurement circuit A1 of this embodiment. 【0068】 On the other hand, in the capacitance measurement circuit A1 of this embodiment, a plurality of detection circuits 20 are provided, and there is no switching circuit in the circuit between one detection circuit 20 and the part to be measured (one detection circuit 20 is directly connected to the part to be measured). Therefore, when measuring the capacitance of the part to be measured, the capacitance of the first parasitic capacitance part becomes smaller than the capacitance of the second parasitic capacitance part in the capacitance measurement circuit Z1 of the comparative example. 【0069】 Therefore, the capacitance measurement circuit A1 of this embodiment can reduce the measurement error caused by parasitic capacitance compared to the capacitance measurement circuit Z1 of the comparative example. Thus, the capacitance measurement circuit A1 of this embodiment can measure the capacitance of the part to be measured with greater accuracy than the capacitance measurement circuit Z1 of the comparative example, thereby improving the accuracy of capacitance measurement. In short, the capacitance measurement circuit A1 of this embodiment can further improve the accuracy of capacitance measurement. 【0070】 Furthermore, in the capacitance measurement circuit A1, the control circuit 10 acquires voltages corresponding to the capacitance of the part to be measured one by one from among the multiple capacitance units 41 to 49 and calculates the capacitance of the part to be measured, thereby reducing measurement errors caused by parasitic capacitance units. Therefore, the capacitance measurement circuit A1 of this embodiment can further improve the accuracy of capacitance measurement. 【0071】The detection voltage Vx of the detection unit 2 is expressed by the following formula (1), where Vdd is the voltage value of a predetermined voltage from the power supply unit 1, Cr is the capacitance of the capacitor 4, and C is the total capacitance of the part under test and the parasitic capacitance part. 【0072】 【0073】 In the capacitance measurement circuit A1 of this embodiment, as can be seen from equation (1), the value of the detection voltage Vx can be increased by decreasing the value of C / Cr, thereby increasing the detection sensitivity of the detection voltage Vx. As a result, the capacitance measurement circuit A1 can achieve high sensitivity of the capacitance of the part to be measured. 【0074】 Furthermore, in the capacitance measurement circuit A1, the value of Cr in equation (1) is constant, so by decreasing the value of C in equation (1), the value of C / Cr in equation (1) can be decreased. 【0075】 In the capacitance measurement circuit A1 of this embodiment, as described above, the capacitance of the parasitic capacitance portion included in the capacitance of the part to be measured is smaller than that of the comparative example capacitance measurement circuit Z1, so the value of C / Cr in equation (1) can be reduced. Therefore, the capacitance measurement circuit A1 of this embodiment can achieve higher sensitivity of the capacitance of the part to be measured than the capacitance measurement circuit Z1 of the comparative example (see Figure 4). In Figure 4, K1 represents the relationship when the capacitance of the parasitic capacitance portion included in the capacitance of the part to be measured (parasitic capacitance) is smallest. In Figure 4, K2 represents the relationship when the parasitic capacitance is larger than that of K1 in Figure 4. In Figure 4, K3 represents the relationship when the parasitic capacitance is larger than that of K2 in Figure 4. 【0076】 (4) Load detection device Hereinafter, the load detection device B1 will be described with reference to Figures 1 and 5 to 8. 【0077】 The load detection device B1 shown in Figure 1 is configured to detect a load P1 (see Figure 8) using a load sensor 50. 【0078】 The load detection device B1 comprises a capacitance measurement circuit A1 and a load sensor 50. 【0079】The load sensor 50 is a capacitive type sensor, and is also called a capacitive pressure sensor element, a capacitive pressure detection sensor element, or a pressure switch element. 【0080】 The load sensor 50 includes a plurality of (three in the example in Figure 1) first conductors 5, a plurality of (three in the example in Figure 1) second conductors 6, a first base member 51 (see Figure 6), a second base member 52 (see Figure 6), and a plurality of capacitance parts 41 to 49. Since the configuration of each of the plurality of first conductors 5 is common, unless otherwise specified, one first conductor 5 will be described below. Similarly, since the configuration of each of the plurality of second conductors 6 is common, unless otherwise specified, one second conductor 6 will be described below. 【0081】 As shown in Figure 5, the first base member 51 has a plate-like shape (for example, a rectangular plate shape). The first base member 51 is elastic and non-conductive. The material of the first base member 51 is, for example, a non-conductive resin. 【0082】 The second conductor 6 has an elongated plate shape. The second conductor 6 is elastic and conductive. The material of the second conductor 6 is, for example, a resin containing a conductive filler. 【0083】 Multiple second conductors 6 are arranged on one surface of the first base member 51. Furthermore, multiple second conductors 6 are arranged in a line along the second direction D2. 【0084】 A connecting wire 8 is electrically connected to one end of the second conductor 6 in the first direction D1. 【0085】 The first conductor 5 is a covered wire. The first conductor 5 includes a linear conductive portion 5a (see Figure 7) and a dielectric 5b (see Figure 7) that covers the surface of the conductive portion 5a. 【0086】 The conductive part 5a is conductive. The material of the conductive part 5a is, for example, copper. The dielectric 5b is nonconductive. The material of the dielectric 5b is, for example, a nonconductive resin. 【0087】The first conductor 5 is arranged across multiple second conductors 6. The multiple first conductors 5 are arranged in a line along the first direction D1. Also, the multiple first conductors 5 are arranged intersecting with the multiple second conductors 6. For example, the multiple first conductors 5 are arranged perpendicular to the multiple second conductors 6. Note that the multiple first conductors 5 are not limited to being arranged perpendicular to the multiple second conductors 6; for example, they may be arranged parallel to the multiple second conductors 6. 【0088】 The first conductor 5 is attached to the first base member 51 by multiple (four in the example of Figure 5) threads 9. More specifically, the first conductor 5 is attached to the first base member 51 by multiple threads 9 so as to overlap with multiple (three in the example of Figure 5) second conductors 6. 【0089】 The material of each of the multiple threads 9 is, for example, a synthetic fiber, a natural fiber, or a blended fiber. 【0090】 A connecting wire 7 is electrically connected to one end of the first conductor 5 in the second direction D2. 【0091】 As shown in Figure 6, the second base member 52 has a plate-like shape (for example, a rectangular plate shape). The second base member 52 is the same size as the first base member 51 when viewed from a third direction D3. 【0092】 The second base member 52 is non-conductive. The material of the second base member 52 is, for example, a non-conductive resin. 【0093】 The second base member 52 is fixed to the first base member 51. For example, the second base member 52 is fixed to the first base member 51 via a connecting member (for example, an adhesive). As a result, the first conductor 5 is sandwiched between the second conductor 6 and the second base member 52 (see Figure 7). 【0094】 Each of the multiple capacitance portions 41 to 49 is interposed at a position where the multiple first conductors 5 and the multiple second conductors 6 intersect (orthogonal in this embodiment), as shown in Figure 5. 【0095】The load sensor 50 can be used in a state where it is inverted from the state shown in Figure 6. As shown in Figure 7, when no load P1 (see Figure 8) is applied to the first base member 51, the force applied between the first conductor 5 and the second conductor 6, and the force applied between the first conductor 5 and the second base member 52 are approximately zero. 【0096】 Furthermore, as shown in Figure 8, when a load P1 is applied to the first base member 51, the first conductor 5 deforms the second conductor 6 and the first base member 51. At this time, at least a portion of the first conductor 5 is enveloped by the second conductor 6. 【0097】 Therefore, in the load sensor 50, the contact area between the first conductor 5 and the second conductor 6 increases, so the capacitance of the capacitance portion between the first conductor 5 and the second conductor 6 changes. Consequently, in the load detection device B1, the load P1 can be detected by measuring the capacitance (capacitance of the part being measured) that changes between the first conductor 5 and the second conductor 6 in the capacitance measurement circuit A1. Furthermore, since the load detection device B1 is equipped with the capacitance measurement circuit A1, the accuracy of capacitance measurement can be further improved. 【0098】 (5) Modified Example The first switch element 1a and the second switch element 1b are each p-channel MOSFETs, but they may be analog switches other than p-channel MOSFETs. The third switch element 1c is an n-channel MOSFET, but it may be an analog switch other than an n-channel MOSFET. 【0099】 Each of the first switch element 1a, the second switch element 1b, and the third switch element 1c is an analog switch, but other types of switches may also be used. For example, each of the first switch element 1a, the second switch element 1b, and the third switch element 1c may be a physical switch. 【0100】 The switch 33 is electrically connected to three capacitance units 41-43, but it may also be electrically connected to two capacitance units, or to four or more capacitance units. In other words, the switch 33 is electrically connected to at least two capacitance units. 【0101】 The switch 34 is electrically connected to three capacitance units 44-46, but it may be electrically connected to two or fewer capacitance units, or to four or more capacitance units. 【0102】 The switch 35 is electrically connected to three capacitance units 47-49, but it may be electrically connected to two or fewer capacitance units, or to four or more capacitance units. 【0103】 Each of the switches 33 to 35 is an analog switch, but they may be other types of switches. For example, each of the switches 33 to 35 may be a physical switch. 【0104】 The number of detection circuits 20 is three, but it may be two or four or more. In other words, the number of detection circuits 20 should be at least two. 【0105】 The detection circuit 20 is electrically connected to three capacitance units, but it may be electrically connected to two or fewer capacitance units, or to four or more capacitance units. In other words, the detection circuit 20 only needs to be electrically connected to at least one capacitance unit. 【0106】 The switching circuit 30 has three switches 33 to 35, but it may have two or fewer switches, or four or more switches. In other words, the switching circuit 30 only needs to have at least one switch (for example, switch 33). 【0107】 The switch circuit 32 is selected such that the first input terminal and the first output terminal are in a conducting state, and the third input terminal and the second output terminal are in a conducting state, but it may also be selected such that the second input terminal and the first output terminal are in a conducting state, and the fourth input terminal and the second output terminal are in a conducting state. 【0108】In this embodiment, the switching circuit 30 has a switch circuit 32, but it does not have to have a switch circuit 32. In this case, the first input terminals of switches 33, 34, and 35 are electrically connected to ground. The second input terminals of switches 33, 34, and 35 are electrically connected to the output terminals of the switch circuit 31. 【0109】 The multiple capacitance units 41 to 49 are arranged in a 3x3 matrix, but they may also be arranged in an 8x8 matrix or a 2x2 matrix. Furthermore, the multiple capacitance units 41 to 49 may be arranged in a configuration other than a 3x3 matrix. For example, the multiple capacitance units may be arranged in a 2x1 linear configuration. 【0110】 The material of the first base member 51 is not limited to a non-conductive resin, but may also be, for example, a non-conductive rubber. 【0111】 The material of the second conductor 6 is not limited to a resin containing a conductive filler, but may also be, for example, rubber containing a conductive filler. 【0112】 The material of the dielectric 5b is not limited to resin; for example, it may be ceramic, metal oxide, or the like. 【0113】 The second base member 52 is non-conductive, but like the first base member 51, it may also be elastic and non-conductive. 【0114】 The number of first conductors 5 is 3, but it may be 2 or 4 or more. In other words, the number of first conductors 5 may be 2 or more. The number of second conductors 6 is 3, but it may be 2 or less or 4 or more. In other words, the number of second conductors 6 may be 1 or more. 【0115】The capacitance measurement circuit A1 measures multiple capacitance portions 41 to 49 in the load sensor 50, but it may also measure capacitance portions other than the multiple capacitance portions 41 to 49 in the load sensor 50. The capacitance measurement circuit A1 may measure capacitance portions such as those in a capacitive touch panel, a semiconductor device, an electrolytic capacitor, or a ceramic capacitor. 【0116】 (Embodiment 2) The capacitance measurement circuit A2 (see Figure 9) according to Embodiment 2 differs from the capacitance measurement circuit A1 according to Embodiment 1 in that it further includes a potential application circuit 60. Regarding the capacitance measurement circuit A2 according to Embodiment 2, components similar to those in the capacitance measurement circuit A1 according to Embodiment 1 are denoted by the same reference numerals and their descriptions are omitted. 【0117】 The capacitance measurement circuit A2 according to Embodiment 2 will be described below with reference to Figure 9. 【0118】 (1) Capacitance measurement circuit Embodiment 2's capacitance measurement circuit A2 further includes a potential application circuit 60. Furthermore, capacitance measurement circuit A2 does not include the switch circuit 31 of capacitance measurement circuit A1. Note that the capacitance measurement circuit A2 of Embodiment 2 may be used in the load detection device B1 instead of the capacitance measurement circuit A1 of Embodiment 1. 【0119】 The potential application circuit (common potential output circuit) 60 is configured to apply (output) a common potential to a plurality of capacitance units 41 to 49. The potential application circuit 60 includes a power supply unit 61, a detection unit 62, a potential generation unit 63, and a variable capacitor 64. 【0120】 The power supply unit (second voltage output unit) 61, like the power supply unit (first voltage output unit) 1, is configured to output a predetermined voltage based on control from the control circuit 10. The power supply unit 61 also supplies a predetermined voltage to the potential generation unit 63 based on control from the control circuit 10. The power supply unit 61 is electrically connected to the control circuit 10 and the potential generation unit 63. 【0121】The detection unit 62 is configured to detect the common potential generated by the potential generation unit 63. The detection unit 62 is, for example, an ADC. The detection unit 62 is electrically connected to the control circuit 10 and the potential generation unit 63. As a result, the control circuit 10 can monitor the common potential generated by the potential generation unit 63 using the detection unit 62. 【0122】 The potential generation unit (second potential output unit) 63 generates a common potential based on a predetermined voltage from the power supply unit 61. The potential generation unit 63 is, for example, VF. The potential generation unit 63 also applies (outputs) the common potential to multiple measurement units (for example, three capacitance units 41 to 43) from among the multiple capacitance units 41 to 49 based on control from the control circuit 10. More specifically, the potential generation unit 63 applies (outputs) the common potential to at least one of the first electrode and second electrode of each of the multiple measurement units based on control from the control circuit 10. As a result, the control circuit 10 can simultaneously acquire the voltage corresponding to the capacitance of each of the multiple measurement units. 【0123】 The potential generation unit 63 is electrically connected to the power supply unit 61, the detection unit 62, and the switching circuit 30. 【0124】 The second and third input terminals of the switch circuit 32 in the switching circuit 30 are electrically connected to the potential generation unit 63. 【0125】 The variable capacitor 64 is an adjustment unit for adjusting the common potential generated by the potential generation unit 63. The first end of the variable capacitor 64 is electrically connected to the potential generation unit 63. The second end of the variable capacitor 64 is electrically connected to ground. 【0126】 The control circuit 10 controls the potential application circuit 60. For example, when the control circuit 10 calculates the capacitance of each of the three capacitance units 41 to 43, it controls the potential application circuit 60 and the switching circuit 30 so that the potential application circuit 60 applies a common potential to the three capacitance units 41 to 43. 【0127】Furthermore, the control circuit 10 controls three detection circuits 21 to 23, which are electrically connected one-to-one with the three capacitance units 41 to 43, and a switching circuit 30, so as to simultaneously acquire the voltage corresponding to the capacitance of each of the three capacitance units 41 to 43. Note that "simultaneously acquiring the voltage corresponding to the capacitance of each of the three capacitance units 41 to 43" does not mean that the voltage corresponding to the capacitance of each of the three capacitance units 41 to 43 is acquired perfectly simultaneously, but that there may be some difference (error). 【0128】 (2) Operation of the Capacitance Measurement Circuit The operation of the capacitance measurement circuit A2 of Embodiment 2 will be described below. For the sake of explanation, the case in which the capacitance of three of the multiple capacitance sections 41 to 49 is measured simultaneously will be described below. Furthermore, in the following, only the differences between the capacitance measurement by the capacitance measurement circuit A2 and the capacitance measurement by the capacitance measurement circuit A1 will be described. 【0129】 The control circuit 10 controls the switching circuit 30 so that the three detection circuits 20 and the three capacitance units 41 to 43 are electrically connected. 【0130】 The control circuit 10 controls the switch 33 so that the first and second electrodes of each of the three capacitance units 41 to 43 are at different potentials. As a result, both electrodes of each of the three capacitance units 41 to 43 are at different potentials. 【0131】 The control circuit 10 controls the potential application circuit 60 so that, after both electrodes of each of the three capacitance units 41 to 43 are at different potentials, the potential application circuit 60 applies a common potential to the three capacitance units 41 to 43. As a result, the potentials of each of the three capacitance units 41 to 43 become the same potential (common potential). 【0132】Furthermore, the control circuit 10 controls the three detection circuits 20 to supply voltage from the power supply unit 1 of each of the three detection circuits 20 to the three capacitance units 41 to 43 after both electrodes of each of the three capacitance units 41 to 43 have become at different potentials. As a result, the three capacitance units 41 to 43 and the three parasitic capacitance units corresponding to each of the three capacitance units 41 to 43 (hereinafter referred to as "the three third parasitic capacitance units") are charged. 【0133】 The control circuit 10 controls the three detection circuits 20 and the switching circuit 30 so as to simultaneously acquire the three detection voltages detected by the three detection units 2 corresponding to each of the three detection circuits 20 after the three capacitance units 41-43 and the three third parasitic capacitance units have been charged (for example, fully charged). The control circuit 10 also calculates the three capacitances (first capacitances) corresponding to each of the three capacitance units 41-43 based on the three detection voltages. 【0134】 The control circuit 10 calculates the first capacitance of each of the three capacitance units 41 to 43, and then controls the switch 33 so that the first and second electrodes of each of the three capacitance units 41 to 43 are at the same potential. As a result, both electrodes of each of the three capacitance units 41 to 43 are at the same potential. 【0135】 Furthermore, the control circuit 10 controls the three detection circuits 20 so that, after both electrodes of each of the three capacitance units 41 to 43 reach the same potential, voltage is supplied from the power supply unit 1 of each of the three detection circuits 20 to the three capacitance units 41 to 43. 【0136】 Since both electrodes of each of the three capacitance units 41 to 43 are at the same potential (meaning the three capacitance units 41 to 43 are effectively eliminated from the circuit), no charge is accumulated in each of the three capacitance units 41 to 43, and only the three third parasitic capacitance units corresponding to each of the three capacitance units 41 to 43 are charged. 【0137】The control circuit 10 controls the three detection circuits 20 and the switching circuit 30 so as to simultaneously acquire the three detection voltages detected by the three detection units 2, each corresponding to one of the three detection circuits 20, after the three third parasitic capacitance units have been charged (for example, fully charged). The control circuit 10 also calculates the three capacitances (second capacitances) corresponding to each of the three capacitance units 41 to 43 based on the three detection voltages. 【0138】 The control circuit 10 calculates the capacitance of each of the three capacitance sections 41 to 43 by the difference between the first capacitance and the second capacitance of each of the three capacitance sections 41 to 43. As a result, the capacitance measurement circuit A2 of Embodiment 2 can simultaneously measure the capacitance of the three capacitance sections 41 to 43. Furthermore, since the capacitance measurement circuit A2 of Embodiment 2 can measure the capacitance of more sections under test than the capacitance measurement circuit A1 of Embodiment 1, the measurement of multiple capacitance sections can be accelerated. 【0139】 Furthermore, in the capacitance measurement circuit A2 of Embodiment 2, similar to the capacitance measurement circuit A1 of Embodiment 1, the three detection circuits 20 are directly connected to the three capacitance sections 41 to 43, respectively. Therefore, the capacitance of each of the three capacitance sections 41 to 43 can be measured with greater accuracy than in the comparative example capacitance measurement circuit Z1 (see Figure 3), where other electronic components are provided. In other words, the capacitance measurement circuit A2 of Embodiment 2 can improve the measurement accuracy of multiple capacitances. 【0140】 Furthermore, in the capacitance measurement circuit A2 of Embodiment 2, when the potential application circuit 60 applies a common potential to the three capacitance sections 41 to 43, the common potential can be adjusted with the variable capacitor 64, thereby further improving the measurement accuracy of multiple capacitances. 【0141】 (3) Modified control circuit 10 simultaneously acquires the voltage corresponding to the capacitance of each of the three capacitance units 41 to 43, but it may also simultaneously acquire the voltage corresponding to the capacitance of each of the three capacitance units 44 to 46, or it may also simultaneously acquire the voltage corresponding to the capacitance of each of the three capacitance units 47 to 49. 【0142】In other words, the control circuit 10 simultaneously acquires the voltage corresponding to the capacitance of each of the multiple units to be measured (in this embodiment, three capacitance units 41 to 43), which are electrically connected one-to-one with the multiple detection circuits 20. More specifically, the control circuit 10 simultaneously acquires the voltage corresponding to the capacitance of each of the multiple units to be measured, which are electrically connected one-to-one with the multiple detection circuits 20 and arranged in a line in one direction (first direction D1 in the example of Figure 5). 【0143】 Furthermore, the control circuit 10 simultaneously acquires the voltage corresponding to the capacitance of each of the three capacitance units 41 to 43, but it may also simultaneously acquire the voltage corresponding to the capacitance of two capacitance units, or it may simultaneously acquire the voltage corresponding to the capacitance of four or more capacitance units. In other words, the control circuit 10 simultaneously acquires the voltage corresponding to the capacitance of two or more capacitance units. 【0144】 The potential application circuit 60 applies a common potential to the three capacitance units 41-43, but for example, it may apply a common potential to two capacitance units, or to four or more capacitance units. In other words, the potential application circuit 60 only needs to apply a common potential to two or more capacitance units. 【0145】 In Embodiment 2, the potential application circuit 60 includes a detection unit 62, but it does not need to include the detection unit 62. Also, in Embodiment 2, the potential application circuit 60 includes a variable capacitor 64, but it does not need to include the variable capacitor 64. 【0146】 (Aspects) The following aspects are disclosed in this specification. 【0147】The capacitance measurement circuit (A1; A2) according to the first embodiment comprises a plurality of detection circuits (20), a switching circuit (30), and a control circuit (10). The plurality of detection circuits (20) are electrically connected to one or more capacitance units from among the plurality of capacitance units (41-43; 44-46; 47-49). The switching circuit (30) switches the connection state between the plurality of capacitance units (41-43; 44-46; 47-49) and the plurality of detection circuits (20). The control circuit (10) controls the plurality of detection circuits (20) and the switching circuit (30). Each of the plurality of detection circuits (20) has a power supply unit (1), a potential generation unit (3), and a detection unit (2). The power supply unit (1) supplies voltage to the unit to be measured, which is the capacitance unit to be measured from among the plurality of capacitance units (41-43; 44-46; 47-49). The potential generation unit (3) generates a potential to bring the first and second electrodes of the part under test to the same potential, and outputs the generated potential to the part under test via the switching circuit (30). The detection unit (2) detects a voltage corresponding to the capacitance of the part under test. The switching circuit (30) has switching units (33; 34; 35). Based on control from the control circuit (10), the switching units (33; 34; 35) switch the first and second electrodes of the part under test to either the same potential or different potentials. The control circuit (10) calculates the capacitance of the part under test by the difference between the first capacitance corresponding to the voltage detected by the detection unit (2) when the first and second electrodes of the part under test are at different potentials, and the second capacitance corresponding to the voltage detected by the detection unit (2) when the first and second electrodes of the part under test are at the same potential. 【0148】 According to this embodiment, the measurement accuracy of capacitance can be further improved. 【0149】 In the second embodiment of the capacitance measurement circuit (A1), the control circuit (10) controls a plurality of detection circuits (20) and switching circuits (30) so as to acquire one voltage each from a plurality of capacitance units (41-43; 44-46; 47-49) corresponding to the capacitance of the unit to be measured. 【0150】 According to this embodiment, the measurement accuracy of capacitance can be further improved. 【0151】The capacitance measurement circuit (A2) according to the third embodiment further comprises a potential application circuit (60) capable of applying a common potential to a plurality of capacitance sections (41-43; 44-46; 47-49) in the first embodiment. When the control circuit (10) calculates the capacitance of two or more sections to be measured, including the section to be measured, from among the plurality of capacitance sections (41-43; 44-46; 47-49), the control circuit (10) controls the potential application circuit (60) so that the potential application circuit (60) applies a common potential to the two or more sections to be measured. 【0152】 According to this embodiment, the voltage corresponding to the capacitance of each of the multiple parts under measurement can be acquired simultaneously. 【0153】 In the fourth embodiment, the capacitance measurement circuit (A2) has, in the third embodiment, an adjustment unit (64) for adjusting the common potential in the potential application circuit (60). 【0154】 According to this embodiment, the measurement accuracy of multiple capacitances can be further improved. 【0155】 In the fifth embodiment, the capacitance measurement circuit (A2) is configured such that, in the third or fourth embodiment, the control circuit (10) controls two or more detection circuits (20) and a switching circuit (30) among a plurality of detection circuits (20) that are electrically connected one-to-one with two or more parts to be measured, so as to simultaneously acquire voltages corresponding to the capacitance of two or more parts to be measured. 【0156】 According to this embodiment, the measurement of multiple capacitance units can be accelerated. 【0157】The load detection device (B1) according to the sixth embodiment comprises a capacitance measurement circuit (A1; A2) according to any one of the first to fifth embodiments, and a load sensor (50). The load sensor (50) has a plurality of capacitance sections (41-43; 44-46; 47-49). The load sensor (50) further comprises a plurality of first conductors (5) and a second conductor (6). The plurality of first conductors (5) are arranged in a line in one direction (D1) and are electrically connected one-to-one with the plurality of detection circuits (20). The second conductor (6) is arranged to intersect with the plurality of first conductors (5) and is electrically connected with a switching circuit (30). Each of the plurality of capacitance sections (41-43; 44-46; 47-49) is interposed at the position where the plurality of first conductors (5) and the second conductor (6) intersect. 【0158】 According to this embodiment, the measurement accuracy of capacitance can be further improved. 【0159】 1 Power supply unit 2 Detection unit 3 Potential generation unit 5 First conductor 6 Second conductor 10 Control circuit 20 Detection circuit 30 Switching circuit 33-35 Switch (switching unit) 41-49 Capacitance unit 50 Load sensor 60 Potential application circuit 64 Variable capacitor (adjustment unit) A1-A2 Capacitance measurement circuit B1 Load detection device D1 First direction (unidirectional)

Claims

1. The device comprises: a plurality of detection circuits electrically connected to one or more capacitance units among a plurality of capacitance units; a switching circuit for switching the connection state between the plurality of capacitance units and the plurality of detection circuits; and a control circuit for controlling the plurality of detection circuits and the switching circuit, each of the plurality of detection circuits having: a power supply unit that supplies voltage to the unit to be measured, which is the capacitance unit to be measured among the plurality of capacitance units; a potential generation unit that generates a potential to bring the first electrode and the second electrode of the unit to be measured to the same potential and outputs the generated potential to the unit to be measured via the switching circuit; and a detection unit that detects a voltage corresponding to the capacitance of the unit to be measured, the switching circuit having a switching unit that switches the first electrode and the second electrode of the unit to be measured to either the same potential or a different potential based on control from the control circuit. The control circuit is a capacitance measurement circuit that calculates the capacitance of the part to be measured by the difference between a first capacitance corresponding to the voltage detected by the detection unit when the first electrode and the second electrode of the part to be measured are at different potentials, and a second capacitance corresponding to the voltage detected by the detection unit when the first electrode and the second electrode of the part to be measured are at the same potential.

2. The capacitance measurement circuit according to claim 1, wherein the control circuit controls the plurality of detection circuits and the switching circuit so as to acquire one voltage each from the plurality of capacitance units corresponding to the capacitance of the unit to be measured.

3. The capacitance measuring circuit according to claim 1, further comprising a potential application circuit capable of applying a common potential to the plurality of capacitance portions, wherein the control circuit controls the potential application circuit so that it applies the common potential to the two or more portions to be measured when calculating the capacitance of two or more portions to be measured from among the plurality of capacitance portions.

4. The capacitance measuring circuit according to claim 3, wherein the potential application circuit has an adjustment unit for adjusting the common potential.

5. The capacitance measuring circuit according to claim 3 or 4, wherein the control circuit controls two or more detection circuits electrically connected one-to-one with the two or more units to be measured, and the switching circuit, so as to simultaneously acquire voltages corresponding to the capacitances of the two or more units to be measured.

6. A load detection device comprising: a capacitance measuring circuit according to claim 1; and a load sensor having a plurality of capacitance sections, wherein the load sensor further comprises: a plurality of first conductors arranged in a line in one direction and electrically connected one-to-one with the plurality of detection circuits; and a second conductor arranged intersecting the plurality of first conductors and electrically connected with the switching circuit, wherein each of the plurality of capacitance sections is interposed at a position where the plurality of first conductors and the second conductor intersect.

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