WO2016139924A1

WO2016139924A1 - Voltage measuring device

Info

Publication number: WO2016139924A1
Application number: PCT/JP2016/001087
Authority: WO
Inventors: 健一郎野坂; 佐々木　健二
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2015-03-03
Filing date: 2016-03-01
Publication date: 2016-09-09
Also published as: JP2016161449A

Abstract

This voltage measuring device is configured to measure a voltage to be measured, i.e., a potential difference between a reference potential and the potential of a conductor. The voltage measuring device is provided with: a first electrode facing the conductor with a space therebetween; a second electrode facing the conductor with a space therebetween; a first capacitor electrically connected to the first electrode and the second electrode; a second capacitor configured to be electrically connected to the second electrode and the reference potential; a first voltage measuring unit configured to measure a first voltage, i.e., a potential difference between the reference potential and the potential of the first electrode; a second voltage measuring unit configured to measure a second voltage, i.e., a potential difference between the reference potential and the potential of the second electrode; and an arithmetic processing unit configured to calculate, using the first voltage and the second voltage, the voltage to be measured. The size of the voltage measuring device can be easily reduced.

Description

Voltage measuring device

The present invention relates to a voltage measuring device that measures a voltage applied to a conductor in a non-contact manner.

A conventional non-contact voltage detection device disclosed in Patent Document 1 includes a first voltage probe, a second voltage probe, a first voltage detection unit, a second voltage detection unit, an arithmetic processing unit, and a signal. And a generator. Each of the voltage probes has a cylindrical internal electrode and a cylindrical external electrode having a diameter larger than that of the internal electrode. The internal electrode is arranged inside the external electrode, and the cable to be measured is inside the internal electrode. It is inserted.

The first voltage detector detects a voltage (potential difference) between the internal electrode and the external electrode of the first voltage probe. The second voltage detector detects a voltage (potential difference) between the internal electrode and the external electrode of the second voltage probe. The signal generator generates an AC test voltage.

The arithmetic processing unit acquires the detection voltage of the first voltage detection unit and the detection voltage of the second voltage detection unit in a state where the AC test voltage is applied to the external electrode. The arithmetic processing unit acquires the detection voltage of the first voltage detection unit and the detection voltage of the second voltage detection unit in a state where the external electrode is grounded. The arithmetic processing unit calculates the voltage applied to the conductor of the cable to be measured from the detection voltage of the first voltage detection unit and the detection voltage of the second voltage detection unit in each state.

JP 2006-242855 A

The voltage measuring device is configured to measure a target voltage that is a potential difference between a conductor potential and a reference potential. The voltage measuring device includes a first electrode facing the conductor with a gap, a second electrode facing the conductor with a gap, a first capacitor electrically connected to the first electrode and the second electrode, A second capacitor configured to be electrically connected to the second electrode and a reference potential, and a first capacitor configured to measure a first voltage which is a potential difference between the potential of the first electrode and the reference potential. A voltage measurement unit, a second voltage measurement unit configured to measure a second voltage that is a potential difference between the potential of the second electrode and a reference potential, and a target voltage is calculated using the first voltage and the second voltage And an arithmetic processing unit configured to do so.

This voltage measuring device is easy to miniaturize.

FIG. 1 is a block diagram of a voltage measuring apparatus according to the first embodiment. FIG. 2 is a conceptual diagram for explaining a usage state of the voltage measuring apparatus according to the first embodiment. FIG. 3 is a circuit diagram showing an equivalent circuit of the voltage measuring apparatus according to the first embodiment. FIG. 4 is a circuit diagram showing an equivalent circuit of the voltage measuring apparatus according to the second embodiment. FIG. 5 is a flowchart showing the operation of the voltage measuring apparatus according to the second embodiment. FIG. 6 is a circuit diagram showing a part of an equivalent circuit of the voltage measuring device according to the third and fourth embodiments. FIG. 7 is a block diagram of a voltage measuring apparatus according to the fifth embodiment. FIG. 8 is a flowchart showing the operation of the voltage measuring apparatus according to the fifth embodiment. FIG. 9 is a circuit diagram showing a part of an equivalent circuit of the voltage measuring apparatus according to the sixth embodiment. FIG. 10 is a block diagram of a voltage measuring apparatus according to the seventh embodiment.

FIG. 1 is a block diagram of a voltage measuring apparatus 1 according to the first embodiment. The voltage measuring apparatus 1 is used for measuring the voltage of the electric wire 10 for supplying AC power from a system power supply (commercial AC power supply) to a load. The voltage measuring apparatus 1 measures a 50 Hz or 60 Hz AC voltage applied to the conductor 11 of the electric wire 10 as the target voltage Vm. However, the voltage measuring device 1 may be configured to use an AC voltage as a target voltage, and is not intended to limit the target voltage to the AC voltage supplied from the system power supply. In addition, the voltage measuring device 1 is not a line voltage between a pair of wires for supplying AC power, but a potential of the conductor 11 of one wire 10 with respect to a reference potential 1R such as a ground potential, that is, a potential of the conductor 11. And the reference potential 1R is measured as the target voltage Vm.

(Embodiment 1)
As shown in FIG. 1, the voltage measuring apparatus 1 according to the first embodiment includes an electrode 2A, an electrode 2B, a capacitor 3A, a capacitor 3B, a voltage measuring unit 4A, a voltage measuring unit 4B, a voltage measuring unit 4C, an arithmetic processing unit 5, and a buffer. 6 and an output unit 7.

The voltage measuring device 1 is configured to measure the target voltage Vm applied to the conductor 11 of the electric wire 10 in a non-contact manner. Therefore, the electrode 2A and the electrode 2B are used in a state where they are not in direct contact with the conductor 11. The electric wire 10 includes a conductor 11 and a coating 12 that covers the conductor 11. The conductor 11 is a single wire made of metal such as copper or copper alloy, for example. The coating 12 is an insulator, and is preferably formed of a synthetic resin material having electrical insulation properties such as vinyl resin.

FIG. 2 is a conceptual diagram for explaining the usage state of the voltage measuring apparatus 1. The

electrodes

2A and 2B have the same configuration and function as voltage measurement probes. As shown in FIG. 2, the electrode 2 A and the electrode 2 B are formed in a sheet shape or a plate shape with a conductive material such as copper, and are arranged so as to be in contact with the surface of the covering 12 of the electric wire 10. The

electrodes

2A and 2B are preferably configured to be curved along the outer peripheral surface of the electric wire 10 so as to be in contact with the coating 12 with almost no gap. In other words, the electrode 2 A and the electrode 2 B are arranged so as to face the conductor 11 through the coating 12 without removing the coating 12 in the electric wire 10 having a structure in which the conductor 11 is covered with the coating 12. Therefore, the distance from each of the electrode 2A and the electrode 2B to the conductor 11 is substantially equal to the thickness dimension of the coating 12. Thus, the

electrodes

2A and 2B are capacitively coupled to the conductor 11 by being spaced from the conductor 11 by the thickness dimension of the covering 12. However, the electrode 2 A and the electrode 2 B may be configured to be formed on a plate-like member having no flexibility and pressed against the coating 12. Alternatively, the electrode 2A and the electrode 2B may be arranged inside the synthetic resin clamp and arranged in the vicinity of the coating 12 by sandwiching the coating 12 with the clamp. The

electrodes

2A and 2B may be provided integrally with the main body 100 of the voltage measuring device 1, but are provided separately from the main body 100 and electrically connected to the main body 100 with a cable. May be.

FIG. 3 shows an equivalent circuit of the voltage measuring apparatus 1. The electrostatic capacity component formed between the electrode 2A and the conductor 11 is called a coupling capacity 20A, and the electrostatic capacity component formed between the electrode 2B and the conductor 11 is called a coupling capacity 20B (see FIG. 3). . The capacitance values of the

coupling capacitors

20A and 20B are the distances from the

electrodes

2A and 2B to the surface of the conductor 11, and the dielectric constant of the inclusion (coating 12) interposed between the

electrodes

2A and 2B and the conductor 11. It depends on. That is, the capacitance values of the

coupling capacitors

20A and 20B are not constant, and change depending on the thickness dimension of the coating 12, the material (dielectric constant) of the coating 12, and the like. Note that an interval is formed between each of the

electrodes

2A and 2B and the conductor 11 so that the

coupling capacitors

20A and 20B are formed. In addition, it is not essential that the coating 12 is interposed between each of the electrode 2A and the electrode 2B and the conductor 11, for example, even if a gap (air) exists between the electrode 2A and the electrode 2B and the conductor 11. Good.

The capacitor 3A has a terminal 30A and a terminal 31A, and is composed of a capacitor such as an electrolytic capacitor, a film capacitor, or a ceramic capacitor having a known capacitance value. A terminal 30A of the capacitor 3A is electrically connected to the electrode 2A and the voltage measuring unit 4A. The terminal 31A of the capacitor 3A is electrically connected to the output terminal 6B of the buffer 6 and the voltage measuring unit 4C (see FIG. 1). A terminal 31A of the capacitor 3A is electrically connected to the electrode 2B through the buffer 6. The capacitor 3B has a terminal 30B and a terminal 31B, and is constituted by a capacitor such as an electrolytic capacitor, a film capacitor, or a ceramic capacitor having a known capacitance value. Terminal 30B of capacitor 3B is electrically connected to electrode 2B and voltage measurement unit 4B. The terminal 31B of the capacitor 3B is electrically connected (grounded) to the reference potential 1R.

The voltage measuring unit 4A is configured to measure a voltage V1 that is a potential difference between the reference potential 1R and the electrode 2A. Similarly, the voltage measuring unit 4B is configured to measure a voltage V2 that is a potential difference between the reference potential 1R and the electrode 2B. The voltage measuring unit 4C is configured to measure a voltage V3 that is a potential difference between the potential of the terminal 31A of the capacitor 3A and the reference potential 1R.

The buffer 6 is preferably composed of any one of a voltage follower circuit, an inverting amplifier circuit, and a non-inverting amplifier circuit. The input terminal 6A of the buffer 6 is electrically connected to the electrode 2B, and the output terminal 6B of the buffer 6 is electrically connected to the terminal 31A of the capacitor 3A. In the following description, it is assumed that the buffer 6 is composed of a voltage follower circuit.

The arithmetic processing unit 5 includes, for example, a microcontroller and a program executed by the microcontroller. The arithmetic processing unit 5 is configured to calculate the target voltage Vm from the voltage values of the voltage V1, the voltage V2, and the voltage V3 by executing a program with a microcontroller.

The output unit 7 has a display device such as a liquid crystal display, for example, and is configured to display the voltage value of the target voltage Vm under the control of the arithmetic processing unit 5 (see FIG. 2). However, since the target voltage Vm is an AC voltage, the value displayed on the output unit 7 is, for example, an effective value, an instantaneous value, an amplitude value, or the like of the target voltage Vm.

As shown in FIG. 3, the terminal 30A of the capacitor 3A is capacitively coupled to the conductor 11 via the electrode 2A and the coupling capacitor 20A. The terminal 30B of the capacitor 3B is capacitively coupled to the conductor 11 via the electrode 2B and the coupling capacitor 20B. That is, since the electrode 2A and the electrode 2B are capacitively coupled to the conductor 11 via the coupling capacitance 20A and the coupling capacitance 20B, respectively, the potential of the electrode 2A and the potential of the electrode 2B become the potential of the conductor 11 (target voltage Vm). Correspondingly, it changes like a sine wave.

The voltage measuring unit 4A samples (samples) a voltage V1 that is a potential difference between the potential of the electrode 2A and the reference potential 1R, and quantizes each sample value (sampling value), thereby obtaining an instantaneous value of the voltage V1. It is configured to measure a certain voltage value. The voltage measuring unit 4A can also calculate the effective value of the voltage V1 as a voltage value from a plurality of instantaneous values.

The voltage measurement unit 4B samples (samples) the voltage V2 which is the potential difference between the potential of the electrode 2B and the reference potential 1R, and quantizes each sample value (sampling value), thereby obtaining an instantaneous value of the voltage V2. It is configured to measure a certain voltage value. The voltage measuring unit 4B can also calculate the effective value of the voltage V2 as a voltage value from a plurality of instantaneous values.

Similarly, the voltage measuring unit 4C samples (samples) a potential difference (voltage V3) between the potential of the terminal 31A of the capacitor 3A and the reference potential 1R, and quantizes each sample value (sampling value). It is configured to measure a voltage value that is an instantaneous value of the voltage V3. Note that the voltage measurement unit 4C can also calculate the effective value of the voltage V3 as a voltage value from a plurality of instantaneous values.

The voltage measuring unit 4A, the voltage measuring unit 4B, and the voltage measuring unit 4C output the measured voltage values (the voltage value of the voltage V1, the voltage value of the voltage V2, and the voltage value of the voltage V3) to the arithmetic processing unit 5.

The arithmetic processing unit 5 stores the voltage value of the voltage V1, the voltage value of the voltage V2, and the voltage value of the voltage V3 in the memory of the microcontroller, and then reads the voltage values from the memory to calculate the target voltage Vm. Configured as follows.

Next, the calculation processing of the target voltage Vm in the calculation processing unit 5 will be described in detail. However, “V1”, “V2”, and “V3” in the following equations represent the voltage value of the voltage V1, the voltage value of the voltage V2, and the voltage value of the voltage V3, respectively. The capacitor 3A has a capacitance value Cin1, the capacitor 3B has a capacitance value Cin2, the coupling capacitor 20A has a capacitance value Cs1, and the coupling capacitor 20B has a capacitance value Cs2. However, when the buffer 6 is composed of an inverting amplifier circuit and the voltage value is an amplitude value or an effective value, it is necessary to replace “V3” in the following formula with “−V3”.

The voltage V2 corresponds to a value obtained by dividing the target voltage Vm by the capacitor 3B and the coupling capacitance 20B, and is expressed by the following equation (1).

The voltage V1 is equal to the sum of the voltage V3 and the value obtained by dividing the difference between the target voltage Vm and the voltage V3 by the capacitor 3A and the coupling capacitor 20A, and is expressed by the following equation (2).

Here, the relationship of β1 = β2 can be satisfied by appropriately setting the capacitance value Cin1 of the capacitor 3A and the capacitance value Cin2 of the capacitor 3B. For example, the two capacitance values Cin1 and Cin2 may be equal to each other, and the capacitance value Cs1 of the coupling capacitor 20A and the capacitance value Cs2 of the coupling capacitor 20B may be equal to each other. Note that the capacitance value Cs1 of the coupling capacitor 20A and the capacitance value Cs2 of the coupling capacitor 20B are substantially equal by aligning the shapes, sizes, materials, and the like of the

electrodes

2A and 2B.

When β1 = β2 = β and subtracting the formula 2 from the formula 1 to delete the target voltage Vm, the following formula 3 is obtained.

The following formula 4 is obtained from the formula 3 above.

When the above formula 4 is substituted into the formula 1 and rearranged, the formula 5 is obtained.

Therefore, the arithmetic processing unit 5 can calculate the target voltage Vm by substituting the measured voltage value of the voltage V1, the voltage value of the voltage V2, and the voltage value of the voltage V3 into the above equation (5). it can. However, since the amplification degree (gain) α of the non-inverting amplifier circuit, the inverting amplifier circuit, or the voltage follower circuit used for the buffer 6 is known, the arithmetic processing unit 5 uses the following equation (6): The voltage value of the voltage V3 can be calculated from the voltage value of the voltage V2.

Therefore, the arithmetic processing unit 5 can calculate the target voltage Vm using at least the voltage value of the voltage V1 and the voltage value of the voltage V2. Therefore, the voltage measuring apparatus 1 of the present embodiment may not include the voltage measuring unit 4C.

Here, there are different advantages depending on whether the buffer 6 is configured by a voltage follower circuit or when the buffer 6 is configured by an inverting amplifier circuit. In the voltage follower circuit, since the output terminal of the operational amplifier is electrically and directly connected to the inverting input terminal of the operational amplifier, the voltage follower circuit is compared with the inverting amplification circuit in which a feedback resistor is connected between the input terminal and the output terminal of the operational amplifier. The error of the amplification degree α is reduced. Therefore, when the voltage follower circuit is used for the buffer 6, the accuracy in calculating the voltage V3 from the voltage V2 can be improved as compared with the case where the inverting amplifier circuit is used for the buffer 6.

On the other hand, when the inverting amplifier circuit is used for the buffer 6, the upper limit (maximum value) of the measurement range of the target voltage Vm is made higher than when the voltage follower circuit and the non-inverting amplifier circuit are used for the buffer 6. Can do. That is, the polarity of the output of the inverting amplifier circuit is inverted, and the sign of the second term on the right side of Equation 3 is negative, so that the voltage V1 is lower than the voltage V2. Therefore, the upper limit of the measurement range of the target voltage Vm is determined by the upper limit of the measurement range of the voltage measurement unit 4B that measures the voltage V2. From the upper limit value Vx2 of the measurement range of the voltage measurement unit 4B, the upper limit value Vmax of the measurement range of the target voltage Vm is expressed by Vmax = Vx2 / β from the equation (1).

When the buffer 6 is a voltage follower circuit or a non-inverting amplifier circuit, the voltage V1 is higher than the voltage V2. Therefore, the upper limit of the measurement range of the target voltage Vm is determined by the upper limit of the measurement range of the voltage measurement unit 4A that measures the voltage V1. Based on the upper limit value Vx1 of the measurement range of the voltage measuring unit 4A, the upper limit value Vmax of the measurement range of the target voltage Vm is expressed by Vmax = Vx1 / {(1 + α) × β} from the formulas 2 and 6. This is lower than when the inverting amplifier circuit is used for the buffer 6.

As described above, the voltage measuring device 1 of the present embodiment measures the voltage V1 and the voltage V2 by the voltage measuring unit 4A and the voltage measuring unit 4B, respectively, in a state where the target voltage Vm is applied to the conductor 11. Then, the arithmetic processing unit 5 calculates the target voltage Vm using the voltage V1 and the voltage V2. Therefore, the voltage measuring apparatus 1 of this embodiment does not need to measure the voltage V1 and the voltage V2 in a state where the AC test voltage is applied to the conductor 11 as in the conventional example. For this reason, the voltage measuring apparatus 1 according to the present embodiment does not require a configuration for generating an AC test voltage, and thus can be more easily reduced in size than the conventional one.

Further, in the voltage measuring apparatus 1 of the present embodiment, the arithmetic processing unit 5 uses the voltage V3 that is a potential difference between the reference potential 1R and the potential of the terminal 31A of the capacitor 3A in addition to the voltage V1 and the voltage V2. It is configured to calculate the voltage Vm. The voltage V3 may be calculated by the calculation processing unit 5 from the voltage V2, or may be measured by the voltage measurement unit 4C.

Further, in the voltage measuring apparatus 1 of the present embodiment, the capacitor 3A and the capacitor 3B are composed of a ratio β1 of the capacitance value Cin1 of the capacitor 3A and the capacitance value Cs1 of the coupling capacitor 20A, and the capacitance of the capacitor 3B and the capacitance value Cin2 It is preferable that the ratio β2 of the value Cs2 is configured to be equal. In particular, the capacitor 3A and the capacitor 3B are preferably configured so that the capacitance values Cin1 and Cin2 are equal to each other. The

electrodes

2A and 2B are preferably configured to make the capacitance value Cs1 of the coupling capacitor 20A equal to the capacitance value Cs2 of the coupling capacitor 20B.

If the voltage measuring device 1 of the present embodiment is configured as described above, an arithmetic expression for calculating the target voltage Vm can be simplified, so that the processing time of the arithmetic processing unit 5 is shortened and the target voltage Vm is calculated. The measurement accuracy can be improved.

As described above, the voltage measuring device 1 is configured to measure the target voltage Vm that is the potential difference between the potential of the conductor 11 and the reference potential 1R. The voltage measuring apparatus 1 includes

electrodes

2A and 2B,

capacitors

3A and 3B,

voltage measuring units

4A and 4B, and an arithmetic processing unit 5. The electrode 2 A is configured to face the conductor 11 with a space therebetween and to generate a coupling capacitance 20 A between the conductor 11. The electrode 2B is configured to face the conductor 11 with a space therebetween and to generate a coupling capacitor 20B between the conductor 11 and the electrode 2B. Capacitor 3A has one terminal 30A electrically connected to electrode 2A and the other terminal 31A electrically connected to electrode 2B. Capacitor 3B has one terminal 30B electrically connected to electrode 2B and the other terminal 31B configured to be electrically connected to reference potential 1R. The voltage measuring unit 4A is configured to measure a voltage V1 that is a potential difference between the potential of the electrode 2A and the reference potential 1R. The voltage measuring unit 4B is configured to measure a voltage V2 that is a potential difference between the potential of the electrode 2B and the reference potential 1R. The arithmetic processing unit 5 is configured to calculate the target voltage Vm using the voltages V1 and V2.

The arithmetic processing unit 5 may be configured to calculate the target voltage Vm using the voltages V1 and V2 and the voltage V3 that is a potential difference between the reference potential 1R and the potential of the other terminal 31A of the capacitor 3A. .

The voltage measuring device 1 may further include a voltage measuring unit 4C configured to measure the voltage V3.

The calculation processing unit 5 may be configured to calculate the voltage V3 from the voltage V2.

The ratio of the capacitance value Cin1 of the capacitor 3A and the capacitance value Cs1 of the coupling capacitor 20A may be equal to the ratio of the capacitance value Cin2 of the capacitor 3B and the capacitance value Cs2 of the coupling capacitor 20B.

The capacitance value Cin1 of the capacitor 3A may be equal to the capacitance value Cin2 of the capacitor 3B. Furthermore, the

electrodes

2A and 2B may be configured such that the capacitance value Cs1 of the coupling capacitor 20A is equal to the capacitance value Cs2 of the coupling capacitor 20B.

The voltage measuring apparatus 1 further includes a buffer 6 that is a voltage follower circuit having an input terminal 6A electrically connected to the electrode 2B and an output terminal 6B electrically connected to the other terminal 31A of the capacitor 3A. It may be.

The voltage measuring apparatus 1 further includes a buffer 6 that is an inverting amplifier circuit having an input terminal 6A electrically connected to the electrode 2B and an output terminal 6B electrically connected to the other terminal 31A of the capacitor 3A. It may be.

(Embodiment 2)
FIG. 4 is a circuit diagram showing an equivalent circuit of the voltage measuring apparatus 1A according to the second embodiment. In FIG. 4, the same reference numerals are assigned to the same parts as those of the voltage measuring apparatus 1 according to the first embodiment shown in FIGS. As shown in FIG. 4, the voltage measurement device 1 A according to the second embodiment is different from the voltage measurement device 1 of the first embodiment in that it further includes a control unit 8 and a switching unit 9. However, the circuit configuration other than the control unit 8 and the switching unit 9 is common to the circuit configuration of the voltage measuring apparatus 1 of the first embodiment.

The switching unit 9 includes, for example, an analog switch having one common contact 90 and two switching

contacts

91 and 92. However, the switching unit 9 is not limited to an analog switch, and may be configured by, for example, a mechanical relay such as an electromagnetic relay or a semiconductor relay. The common contact 90 is electrically connected to the terminal 31A of the capacitor 3A. The switching contact 91 is electrically connected to the output terminal 6 B of the buffer 6. The switching contact 92 is electrically connected (grounded) to the reference potential 1R. The switching unit 9 connects the common contact 90 to the switching contact 91 and disconnects from the switching contact 92, and the second connection connects the common contact 90 to the switching contact 92 and disconnects from the switching contact 91. The state can be switched. The switching unit 9 can selectively connect one of the switching

contacts

91 and 92 to the common contact 90.

The control unit 8 is configured to control the switching unit 9 in response to an instruction from the arithmetic processing unit 5 and to switch the switching unit 9 between the first connection state and the second connection state. The control unit 8 may be configured by a microcontroller that constitutes the arithmetic processing unit 5, or may be configured by a logic circuit independent of the arithmetic processing unit 5. In the equivalent circuit shown in FIG. 4, the output unit 7 is connected to the arithmetic processing unit 5 via the control unit 8, but the output unit 7 may be directly connected to the arithmetic processing unit 5.

Next, the operation of the voltage measuring apparatus 1A according to the second embodiment will be described. FIG. 5 is a flowchart showing the operation of the voltage measuring apparatus 1 A and shows the processing of the arithmetic processing unit 5.

First, the arithmetic processing unit 5 instructs the control unit 8 to switch the switching unit 9 to the second connection state (step S1). In the second connection state, the arithmetic processing unit 5 causes the voltage measurement unit 4A and the voltage measurement unit 4B to measure the voltage V1 and the voltage V2, respectively, and takes in the voltage values of the voltage V1 and the voltage V2 (step S2). The arithmetic processing unit 5 stores the acquired voltage value in a memory.

Subsequently, the arithmetic processing unit 5 instructs the control unit 8 to switch the switching unit 9 to the first connection state (step S3). In the first connection state, the arithmetic processing unit 5 causes the voltage measurement unit 4A, the voltage measurement unit 4B, and the voltage measurement unit 4C to measure the voltage V1, the voltage V2, and the voltage V3, respectively, and the measured voltage V1 and voltage V2 are measured. And the voltage value of voltage V3 is taken in (step S4). The arithmetic processing unit 5 stores the acquired voltage value in a memory.

The calculation processing unit 5 reads the voltage value stored in the memory and calculates the target voltage Vm by the following calculation (step S5).

The voltage value Vmb of the target voltage Vm, the voltage value V1b of the voltage V1, and the voltage value V2b of the voltage V2 in the second connection state satisfy the following Expression 7 and Expression 8.

Eq. 9 is obtained by eliminating Vmb from Eq. 7 and Eq.

On the other hand, the voltage value Vma of the target voltage Vm, the voltage value V1a of the voltage V1, and the voltage value V2a of the voltage V2 in the first connection state satisfy the following Expression 10 and Expression 11.

If the formula of formula 9 is substituted into the formula of formula 11 and rearranged, the formula of formula 12 is obtained.

When the formula of formula 12 is substituted into the formula of formula 10 and rearranged, the formula of formula 13 is obtained.

Therefore, the voltage value Vma of the target voltage Vm in the first connection state and the voltage value Vmb of the target voltage Vm in the second connection state are obtained by substituting the formula 13 into the formula 11 and the formula 7. They are obtained from the following formulas 14 and 15, respectively.

The expressions 14 and 15 do not include the capacitance value Cin1 of the capacitor 3A, the capacitance value Cin2 of the capacitor 3B, the capacitance value Cs1 of the coupling capacitor 20A, and the capacitance value Cs2 of the coupling capacitor 20B. Only the voltage values of V2 and V3 are included. Therefore, even when it is difficult for the arithmetic processing unit 5 to satisfy the relationship of β1 = β2 by calculating the voltage values Vma and Vmb of the target voltage Vm from the formulas (14) and (15), A decrease in measurement accuracy of the target voltage Vm can be suppressed. However, even in the voltage measuring apparatus 1A according to the second embodiment, if the value obtained by multiplying the voltage value of the voltage V2 by the amplification degree α of the buffer 6 is used as the voltage value of the voltage V3, the voltage measuring unit 4C may not be provided. .

As described above, the voltage measuring apparatus 1A includes the first connection state in which the other terminal 31A of the capacitor 3A is electrically connected to the capacitor 3B, and the other terminal 31A of the capacitor 3A is disconnected from the capacitor 3B. Is further provided with a switching unit 9 configured to switch between the second connection state and the second connection state. The arithmetic processing unit 5 is configured to calculate the target voltage Vm using at least the voltages V1 and V2 in the first connection state and the voltages V1 and V2 in the second connection state.

(Embodiment 3)
FIG. 6 is an equivalent circuit around the

capacitors

3A and 3B of the voltage measuring apparatus 1B according to the third embodiment. In FIG. 6, the same reference numerals are assigned to the same parts as those of the voltage measuring apparatus 1 according to the first embodiment shown in FIG. The voltage measuring device 1B has a circuit configuration common to the voltage measuring device 1 according to the first embodiment.

In the voltage measuring apparatus 1 of the first embodiment, stray capacitance may occur between the

electrodes

2A and 2B and the ground, or between the wiring connecting the

electrodes

2A and 2B to the main body 100 and the ground (FIG. 2). In the voltage measurement apparatus 1B according to the third embodiment, these stray capacitances are taken into consideration. In the voltage measuring apparatus 1B, the stray capacitance 21A is generated between the electrode 2A or the wiring from the electrode 2A to the main body 100 and the reference potential 1R. Similarly, a stray capacitance 21B is generated between the electrode 2B or the wiring from the electrode 2B to the main body 100 and the reference potential 1R (see FIG. 6). When the

stray capacitances

21A and 21B have non-negligible values with respect to the capacitance values of the

capacitors

3A and 3B and the capacitance values of the coupling capacitance 20A and the coupling capacitance 20B, in the calculations described in the first and second embodiments, Measurement accuracy is reduced.

Therefore, the voltage measurement apparatus 1B according to the third embodiment is configured to suppress a decrease in measurement accuracy by calculating the target voltage Vm in consideration of the stray capacitance 21A and the stray capacitance 21B.

Next, the calculation processing of the target voltage Vm in the calculation processing unit 5 will be described in detail. However, in the following description, the stray capacitance 21A has a capacitance value Cf1, and the stray capacitance 21B has a capacitance value Cf2. In the third embodiment, it is assumed that the capacitance value Cf1 of the stray capacitance 21A is equal to the capacitance value Cf2 of the stray capacitance 21B.

FIG. 6 shows a portion including only the electrode 2A, the electrode 2B, the capacitor 3A, the capacitor 3B, the

coupling capacitors

20A and 20B, and the

stray capacitors

21A and 21B in the equivalent circuit of the voltage measuring apparatus 1B according to the third embodiment. . As can be seen from the equivalent circuit of FIG. 6, the target voltage Vm is divided by the parallel circuit of the capacitor 3B and the stray capacitance 21B and the coupling capacitance 20B, and the voltage division ratio βm is expressed by the following equation (16). Is done.

Since the voltage V3 is divided by the parallel circuit of the coupling capacitance 20A and the stray capacitance 21A and the capacitor 3A, if the voltage division ratio is (1-βr), βr is expressed by the following equation (17). .

Further, the voltage V1 and the voltage V2 are expressed by the following equations 18 and 19 using the voltage dividing ratios βm and βr.

Further, subtracting the formula 19 from the formula 18 and rearranging the formula yields the following formula 20.

From the above equation (20), the following equation (21) is obtained.

The partial pressure ratio βm is expressed as the following formula 22 by deleting Cs1 from the formula 16 and the formula 17 and substituting the formula 21.

Further, the target voltage Vm is obtained from the following equation (23) from the equation (19) and the equation (22).

In the above equation 23, the arithmetic processing unit 5 can calculate the target voltage Vm as long as the capacitance value Cf1 of the stray capacitance 21A is known.

Therefore, in the voltage measurement device 1B according to the third embodiment, a correction program for performing processing for calculating the capacitance value Cf1 or the capacitance value Cf2 may be stored in the memory of the microcontroller that constitutes the arithmetic processing unit 5. preferable. For example, in the manufacturing factory of the voltage measuring device 1B, the correction program is executed by the microcontroller of the arithmetic processing unit 5 in a state where an AC reference voltage having a known voltage value (target voltage Vm) is applied to the conductor 11. Then, the arithmetic processing unit 5 calculates Equation 23 from the measured voltage value of the voltage V1, the voltage value of the voltage V2, the voltage value of the voltage V3, the capacitance value Cin1 of the capacitor 3A, and the voltage value of the target voltage Vm. Using this, the capacitance value Cf1 is calculated. The microcontroller of the arithmetic processing unit 5 stores the calculated capacitance value Cf1 in the memory of the microcontroller, and then ends the execution of the correction program.

The voltage measurement device 1B according to the third embodiment calculates the capacitance value Cf1 of the stray capacitance 21A in advance as described above, so that the calculated capacitance can be obtained even when the stray capacitance 21A and the stray capacitance 21B exist. The target voltage Vm can be measured with high accuracy based on the value Cf1 and the equation of Equation 23, and a decrease in measurement accuracy can be suppressed.

As described above, the arithmetic processing unit 5 includes the capacitance value Cf1 of the stray capacitance 21A generated between the electrode 2A and the reference potential 1R, and the capacitance value Cf2 of the stray capacitance 21B generated between the electrode 2B and the reference potential 1R. Is used to correct the calculated target voltage Vm.

The arithmetic processing unit 5 is configured to calculate the capacitance values Cf1 and Cf2 of the

stray capacitances

21A and 21B using the voltages V1 and V2 and the known voltage in a state where a known voltage is applied to the conductor. It may be.

(Embodiment 4)
Since the voltage measuring device according to the fourth embodiment has a common circuit configuration with the voltage measuring device 1A according to the second embodiment, the same components are denoted by the same reference numerals, and illustration and description thereof are omitted.

Also in the voltage measurement apparatus 1A of the second embodiment, the stray capacitance 21A and the stray capacitance 21B are provided between the

electrodes

2A and 2B and the ground, or between the wiring connecting the

electrodes

2A and 2B to the main body 100 and the ground. May occur.

Therefore, the voltage measurement device according to the fourth embodiment takes into account the stray capacitance 21A and the stray capacitance 21B, and the voltage value Vma of the target voltage Vm in the first connection state and the voltage value of the target voltage Vm in the second connection state. By calculating Vmb, it is configured to suppress a decrease in measurement accuracy.

Next, the calculation processing of the voltage values Vma and Vmb of the target voltage Vm in the calculation processing unit 5 will be described in detail. However, in the following description, the stray capacitance 21A has a capacitance value Cf1, and the stray capacitance 21B has a capacitance value Cf2.

The partial pressure ratio β1m is expressed by the following equation (24).

Similarly, the partial pressure ratio β2m is expressed by the following equation (25).

On the other hand, the partial pressure ratio βr is expressed by the following equation (26).

As described in the second embodiment, the voltage value Vmb of the target voltage Vm, the voltage value V1b of the voltage V1, and the voltage value V2b of the voltage V2 in the second connection state are expressed by the following equations (27) and (28). Fulfill.

When the voltage value Vmb is deleted from the equation (27) and the equation (28), the equation (29) is obtained.

On the other hand, the voltage value Vma of the target voltage Vm, the voltage value V1a of the voltage V1, and the voltage value V1b of the voltage V2 in the first connection state satisfy the following Expression 30 and Expression 31.

When the formula of formula 29 is substituted into the formula of formula 31 and rearranged, the formula of formula 32 is obtained.

When the formula of formula 32 is substituted into the formula of formula 30 and rearranged, the formula of formula 33 is obtained.

The partial pressure ratio β1m is expressed as the following equation 34 by deleting Cs1 from the equations 24 and 26 and substituting the equation 33.

Therefore, the voltage value Vma of the target voltage Vm in the first connection state can be obtained from the following equation 35 obtained by substituting the equation 29 and the equation 34 into the equation 31.

Similarly, the voltage value Vmb of the target voltage Vm in the second connection state can be obtained from the following equation 36 obtained by substituting the equation 34 into the equation 27.

If the capacitance value Cf1 of the stray capacitance 21A is found in the equation 35 and the equation 36, the arithmetic processing unit 5 can calculate the voltage values Vma and Vmb of the target voltage Vm. However, as in the third embodiment, it is preferable that the arithmetic processing unit 5 calculates the capacitance value Cf1 of the stray capacitance 21A in advance by executing the correction program.

(Embodiment 5)
FIG. 7 is a circuit diagram showing an equivalent circuit of the voltage measuring apparatus 1C according to the fifth embodiment. In FIG. 7, the same reference numerals are assigned to the same parts as those of the voltage measuring apparatus 1 according to the first embodiment shown in FIGS. The voltage measuring device 1C is electrically connected to the input terminal 106A electrically connected to the electrode 2B and the other terminal 31A of the capacitor 3A instead of the buffer 6 of the voltage measuring device 1 shown in FIGS. And a variable gain amplifier circuit 106 having an output terminal 106B. The variable gain amplifier circuit 106 has a variable amplification factor αV. Voltage measurement apparatus 1 C further includes a control unit 108 that controls amplification factor αV of variable gain amplification circuit 106.

FIG. 8 is a flowchart showing the operation of the voltage measuring apparatus 1C. The control unit 108 sets the amplification factor αV of the variable gain amplifier circuit 106 to the amplification factor αA (step S101). The

voltage measuring units

4A, 4B, and 4C measure the voltage values V1A, V2A, and V3A of the voltages V1, V2, and V3 when the amplification factor αV of the variable gain amplifier circuit 106 is the amplification factor αA (step S102). The control unit 108 sets the gain αV of the variable gain amplifier circuit 106 to the gain αB (step S103). The

voltage measuring units

4A, 4B, and 4C measure the voltage values V1B, V2B, and V3B of the voltages V1, V2, and V3 when the amplification factor αV of the variable gain amplifier circuit 106 is the amplification factor αB (step S104). Thereby, the arithmetic processing unit 5 obtains the voltage values V1A and V1B of the voltage V1, the voltage values V2A and V2B of the voltage V2, and the voltage values V3A and V3B of the voltage V3. The arithmetic processing unit 5 calculates the target voltage Vm based on the voltage values V1A and V1B of the voltage V1, the voltage values V2A and V2B of the voltage V2, and the voltage values V3A and V3B of the voltage V3 (step S105).

Note that the voltage measuring apparatus 1C may not include the voltage measuring unit 4C. In this case, the voltage measuring apparatus 1C can obtain the voltage values V3A and V3B of the voltage V3 by multiplying the voltage values V1A and V2B of the voltage V2 by the amplification factors αA and αB, respectively.

The operation in which the arithmetic processing unit 5 calculates the target voltage Vm in step S105 will be described below.

The voltage values V1A and V1B of the voltage V1 and the voltage V2 by the voltage dividing ratios β1 and β2 expressed using the capacitance values Cin1 and Cin2 of the

capacitors

3A and 3B and the capacitance values Cs1 and Cs2 of the

coupling capacitors

20A and 20B. Values V2A and V2B are expressed by equations 37 to 40.

Since VmA = V2A / β2 is established from the equation (38), the voltage value V1A is expressed as follows when substituted into the equation (37).

If the formula of formula 41 is arranged with respect to β1, the formula of formula 42 is obtained.

Similarly, the following formula is obtained from the formulas 39 and 40.

If β1 is deleted from the equations 42 and 43 and β2 is arranged, the following equation 44 is obtained.

As shown in Equation 44, the voltage division ratio β2 is obtained from the voltages V1 to V3 to be measured.

Therefore, the voltage value VmA of the target voltage Vm of the conductor 11 in the state where the amplification factor αV is the amplification factor αA and the amplification factor αV is the amplification factor αB, from the obtained voltage dividing ratio β2, Equations 38, and Equation 40. VmB is required.

Since V3A = αA × V2A and V3B = αB × V2B, the voltage values VmA and VmB can be obtained without measuring the voltage values V3A and V3B.

As described above, the voltage measuring device 1 C according to the fifth embodiment does not need to include an AC voltage generation unit, and can measure the AC voltage of the conductor 11 with a simple configuration without being directly connected to the conductor 11 of the wire 10. Become.

The voltage values V3A and V3B of the voltage V3 can be calculated from the amplification factors αA and αB and the voltage values V2A and V2B of the voltage V2. However, since the voltage V3 can be obtained without error due to amplification by directly measuring the voltage V3 by the voltage measuring unit 4C, the target voltage Vm can be measured with a simple configuration with high accuracy.

(Embodiment 6)
FIG. 9 is an equivalent circuit around the

capacitors

3A and 3B of the voltage measuring apparatus 1D according to the sixth embodiment. 9, the same reference numerals are assigned to the same portions as those of the voltage measuring device 1C according to the fifth embodiment shown in FIG. The voltage measuring device 1D has a common circuit configuration with the voltage measuring device 1D according to the fifth embodiment.

In the voltage measurement apparatus 1D of the fifth embodiment, stray capacitance may occur between the

electrodes

2A and 2B and the ground, or between the wiring connecting the

electrodes

2A and 2B to the main body 100 and the ground. In the voltage measurement apparatus 1D according to the sixth embodiment, these stray capacitances are taken into consideration. In the voltage measuring device 1D, the stray capacitance 21A is generated between the electrode 2A or the wiring from the electrode 2A to the main body 100 and the reference potential 1R. Similarly, the

stray capacitances

21A and 21B in which the stray capacitance 21B is generated between the electrode 2B or the wiring from the electrode 2B to the main body 100 and the reference potential 1R have capacitance values Cf1 and Cf2, respectively. When the stray capacitance 21A exists, the target voltage Vm is divided by the capacitance value Cs1 with respect to the parallel combined capacitance (Cin1 + Cf1) of the capacitance values Cin1 and Cf1, and thus a voltage division ratio that is a ratio between the target voltage Vm and the voltage V1. β1m is expressed by the equation (46).

Similarly, when the stray capacitance 21B exists, the target voltage Vm is divided by the capacitance value Cs2 with respect to the parallel combined capacitance (Cin2 + Cf2) of the capacitance values Cin2 and Cf2, so that the ratio of the target voltage Vm to the voltage V2 is obtained. A certain partial pressure ratio β2m is expressed by the equation (47).

On the other hand, V3 is divided by the capacitance value Cin1 with respect to the parallel combined capacitance value (Cs1 + Cf1) of the capacitance values Cs1 and Cf1, so if the voltage dividing ratio between the voltage V3 and the voltage V1 is (1−β1r), β1r Is as shown in the equation 48.

The voltage values V1A and V1B of the voltage V1 and the voltage values V2A and V2B of the voltage V2 are expressed by equations 49 to 52.

Since VmA = V2A / β2m is established from the formula 50, the following formula is obtained by substituting into the formula 49.

If this formula is arranged for β1m and β2m, the formula 54 is obtained.

Mathematical formula 55 is obtained similarly from mathematical formulas 51 and 52.

[Equation 56 is obtained by eliminating β1m and β2m from the equations 54 and 55 and rearranging β1r.

[Equation 57 is obtained by eliminating Cs1 from the equations 46 and 48 and organizing β1m.

When the formula 56 is substituted into the formula 57, the formula 58 is obtained.

The following formula is obtained from the formula of Formula 49.

Therefore, when formulas 56 and 58 are substituted and arranged, formula 60 is obtained.

The following is obtained from the equation of Formula 51.

Therefore, substituting and arranging the formulas 56 and 58 yields the following formula.

If the capacitance value Cf1 of the stray capacitance 21A is known from the formulas 60 and 62, the voltage values VmA and VmB of the target voltage Vm can be calculated.

Further, if the voltages V1 to V3 to which the target voltage Vm having a known voltage value is applied in the manufacturing process or the like are measured in advance and are combined with the known capacitance value Cin1, the capacitance of the stray capacitance 21A is calculated from the formulas 60 and 62. The value Cf1 can be determined.

Thus, if the capacitance value Cf1 of the stray capacitance 21A is known, correction by the stray capacitance 21A that affects the voltage estimation accuracy is possible, and the voltage estimation accuracy can be improved.

Even when the capacitance value Cf1 of the stray capacitance 21A is unknown, the target voltage Vm can be corrected by the stray capacitance 21A that affects the voltage estimation accuracy, and the voltage estimation accuracy can be improved.

(Embodiment 7)
FIG. 10 is a block diagram of a voltage measuring apparatus 1E according to the seventh embodiment. 10, the same parts as those of the voltage measuring apparatus 1C according to the fifth embodiment shown in FIG. The voltage measuring device 1E includes a variable gain amplifying circuit 406 instead of the variable gain amplifying circuit 106 of the voltage measuring device 1C according to the fifth embodiment shown in FIG. The variable gain amplifier circuit 406 includes

amplifier circuits

206 and 306 and a switching unit 109. The amplifier circuit 206 has an input terminal 206A electrically connected to the electrode 2B and an output terminal 206B. The amplifier circuit 206 has an amplification factor αA. The amplifier circuit 306 has an input terminal 306A electrically connected to the electrode 2B, and an output terminal 306B. The amplifier circuit 306 has an amplification factor αB. The switching unit 109 has switching

contacts

191 and 192 and a common contact 190. The control unit 108 switches the common contact 190 from the first connection state in which the common contact 190 is disconnected from the switching contact 192 and connected to the switching contact 191. It is configured to switch between the second connection state disconnected from the contact 191 and connected to the switching contact 192. In the first connection state, the other terminal 31A of the capacitor 3A is disconnected from the output terminal 306B of the amplifier circuit 306 and electrically connected to the output terminal 206B of the amplifier circuit 206. In the second connection state, the other terminal 31A of the capacitor 3A is disconnected from the output terminal 206B of the amplifier circuit 206 and electrically connected to the output terminal 306B of the amplifier circuit 306. Thereby, the variable gain amplifier circuit 406 operates in the same manner as the variable gain amplifier circuit 106 according to the fifth embodiment, and the same effect can be obtained.

1, 1A, 1B Voltage measuring device 1R Reference potential 2A Electrode (first electrode)
2B electrode (second electrode)
3A capacitor (first capacitor)
3B capacitor (second capacitor)
4A Voltage measurement unit (first voltage measurement unit)
4B Voltage measurement unit (second voltage measurement unit)
4C voltage measurement unit (third voltage measurement unit)
5 Arithmetic processor 6 Buffer (Voltage follower circuit, inverting amplifier circuit)
9 Switching unit 10 Electric wire 11 Conductor 20A Coupling capacity (first coupling capacity)
20B coupling capacity (second coupling capacity)
21A stray capacitance (first stray capacitance)
21B stray capacitance (second stray capacitance)
106 variable gain amplifier circuit 206 amplifier circuit (first amplifier circuit)
306 Amplifier circuit (second amplifier circuit)
406 Variable gain amplifier circuit 109 switching unit Vm target voltage V1 voltage (first voltage)
V2 voltage (second voltage)
V3 voltage (third voltage)

Claims

A voltage measuring device configured to measure a target voltage that is a potential difference between a potential of a conductor and a reference potential,
A first electrode configured to face the conductor at an interval and to create a first coupling capacitance with the conductor;
A second electrode configured to face the conductor at an interval and to generate a second coupling capacitance between the conductor;
A first capacitor having one terminal electrically connected to the first electrode and the other terminal electrically connected to the second electrode;
A second capacitor having one terminal electrically connected to the second electrode and the other terminal configured to be electrically connected to the reference potential;
A first voltage measuring unit configured to measure a first voltage that is a potential difference between the potential of the first electrode and the reference potential;
A second voltage measuring unit configured to measure a second voltage that is a potential difference between the potential of the second electrode and the reference potential;
An arithmetic processing unit configured to calculate the target voltage using the first voltage and the second voltage;
A voltage measuring device comprising:
The arithmetic processing unit calculates the target voltage using the first voltage, the second voltage, and a third voltage that is a potential difference between the reference potential and the potential of the other terminal of the first capacitor. The voltage measuring device according to claim 1, wherein the voltage measuring device is configured to calculate.
The voltage measurement device according to claim 2, further comprising a third voltage measurement unit configured to measure the third voltage.
The voltage measurement device according to claim 2, wherein the arithmetic processing unit is configured to calculate the third voltage from the second voltage.
A first connection state in which the other terminal of the first capacitor is electrically connected to the second capacitor; and the other terminal of the first capacitor is disconnected from the second capacitor and the reference potential is A switching unit configured to switch between a second connection state and an electrical connection state;
The arithmetic processing unit includes at least the voltage value of the first voltage and the voltage value of the second voltage in the first connection state, and the voltage value of the first voltage and the second voltage value in the second connection state. The voltage measuring device according to any one of claims 1 to 4, wherein the voltage measurement device is configured to calculate the target voltage using a voltage value of a voltage.
The ratio between the capacitance value of the first capacitor and the capacitance value of the first coupling capacitance is equal to the ratio of the capacitance value of the second capacitor and the capacitance value of the second coupling capacitance. The voltage measuring device according to claim 1.
The capacitance value of the first capacitor is equal to the capacitance value of the second capacitor,
The voltage measurement device according to claim 6, wherein the first electrode and the second electrode are configured such that a capacitance value of the first coupling capacitance is equal to a capacitance value of the second coupling capacitance.
The voltage follower circuit further comprising: an input terminal electrically connected to the second electrode; and an output terminal electrically connected to the other terminal of the first capacitor. The voltage measuring device according to any one of the above.
The inverting amplifier circuit further comprising an input terminal electrically connected to the second electrode and an output terminal electrically connected to the other terminal of the first capacitor. The voltage measuring device according to any one of the above.
A variable gain amplifier circuit having an input terminal electrically connected to the second electrode and an output terminal electrically connected to the other terminal of the first capacitor and having a variable gain. In addition,
The arithmetic processing unit includes at least a voltage value of the first voltage and a voltage value of the second voltage when the amplification factor of the variable gain amplification circuit is a first amplification factor, and the variable gain amplification circuit. The target voltage is calculated using the voltage value of the first voltage and the voltage value of the second voltage when the amplification factor is a second amplification factor different from the first amplification factor. The voltage measuring device according to claim 1, wherein
The arithmetic processing unit includes at least the voltage value of the first voltage, the voltage value of the second voltage, and the first capacitor when the gain of the variable gain amplifier circuit is the first gain. A voltage value of a third voltage that is a potential difference between the potential of the other terminal of the second terminal and the reference potential, and a voltage of the first voltage when the amplification factor of the variable gain amplifier circuit is the second amplification factor. The voltage measurement device according to claim 10, configured to calculate the target voltage using a value, a voltage value of the second voltage, and a voltage value of the third voltage.
The voltage measuring device according to claim 11, further comprising a third voltage measuring unit that measures the third voltage.
The voltage measurement device according to claim 11, wherein the arithmetic processing unit is configured to calculate the third voltage from the second voltage.
The variable gain amplifier circuit includes:
A first amplifier circuit having an input terminal electrically connected to the second electrode and an output terminal and having the first amplification factor;
A second amplifier circuit having an input terminal electrically connected to the second electrode and an output terminal and having the second amplification factor;
A first connection state in which the other terminal of the first capacitor is disconnected from the output terminal of the second amplifier circuit and electrically connected to the output terminal of the first amplifier circuit; The other terminal of the capacitor is disconnected from the output terminal of the first amplifier circuit and switched to a second connection state in which the capacitor is electrically connected to the output terminal of the second amplifier circuit. A switching unit;
The voltage measuring device according to claim 10, comprising:
The arithmetic processing unit includes a capacitance value of a first stray capacitance generated between the first electrode and the reference potential, and a capacitance value of a second stray capacitance generated between the second electrode and the reference potential. The voltage measurement device according to claim 1, wherein the voltage measurement device is configured to correct the calculated target voltage using the.
The arithmetic processing unit uses the first voltage, the second voltage, and the known voltage in a state where a known voltage is applied to the conductor, and the capacitance value of the first stray capacitance and the first voltage The voltage measurement device according to claim 15, wherein the voltage measurement device is configured to calculate a capacitance value of two stray capacitances.