Voltmeter, voltage measurement method, wattmeter, and arithmetic logic device

Abstract

To provide technology with which it is possible to accurately measure the voltage of an electric wire connected to an AC power supply from the outside of an insulation coating without being affected by its thickness.SOLUTION: Provided is a voltmeter for measuring the voltage of an electric wire connected to an AC power supply and covered with an insulation coating. The voltmeter comprises: a voltage detection electrode for detecting the potential of the electric wire from the outside of the insulation coating; a reference potential output source for outputting at least a first reference potential and a second reference potential; a voltage value output unit for outputting a first voltage value representing a potential difference between at least the detection potential outputted from the voltage detection electrode and the first reference potential and a second voltage value representing a potential difference between the detection potential and the second reference potential; and a measurement voltage calculation unit for calculating the measurement value of voltage of the electric wire by using at least the first reference potential, the second reference potential, the first voltage value, and the second voltage value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a voltmeter, a voltage measuring method, a power meter, and an arithmetic device. [Background technology]

[0002] Conventionally, a method for measuring the voltage of a covered conductor has been known in which the voltage is measured from outside the covering, i.e., in a non-contact manner with respect to the conductor, for the purpose of ensuring safety, etc. When measuring voltage in this manner, the covering located between the conductor and the detection electrode functions as a capacitor, and the detected voltage does not represent an accurate line voltage due to the influence of the capacitance. For this reason, a technique is known that attempts to measure the line voltage accurately in a non-contact manner by first measuring the voltage of an uncovered conductor and then using the measured value to calibrate the voltage detected in a non-contact manner (e.g., Patent Document 1, etc.).

[0003] However, in the technology described in Patent Document 1, the position of the probe equipped with the detection electrode placed on the electric wire, the thickness of the wire coating, etc. change over time, and if this causes a change in the capacitance of the coating, it affects the measured voltage value. In other words, there was a problem that the accuracy of the measured value decreases as time passes after the probe is installed. In addition, the method of Patent Document 1 requires that the voltage of the conductor be measured in advance by a contact method in order to obtain a calibration value, which is accompanied by a problem of danger during such work. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 63-238466 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a technique that enables accurate measurement of the voltage of an electric wire connected to an AC power source from outside the insulating coating without being affected by its thickness. [Means for solving the problem]

[0006] A voltmeter according to one aspect of the present disclosure includes: A voltmeter for measuring the voltage of an insulated electric wire connected to an AC power source, comprising: a voltage detection electrode for detecting a potential of the electric wire from outside the insulating coating; a reference potential output source that outputs at least a first reference potential and a second reference potential; a voltage value output unit that outputs a first voltage value, which is a potential difference between the detection potential output from at least the voltage detection electrode and the first reference potential, and a second voltage value, which is a potential difference between the detection potential and the second reference potential; a measurement voltage calculation unit that calculates a measurement value of the voltage of the electric wire using at least the first reference potential, the second reference potential, the first voltage value, and the second voltage value; Equipped It is a voltmeter.

[0007] According to this configuration, the line voltage of the electric wire can be calculated, for example, by a linear approximation method, using a plurality of voltage values ​​for measurement processing obtained from the difference between a plurality of different reference potentials output by the reference potential output source and the potential detected by the detection electrode. Note that, hereinafter, calculating the voltage of the electric wire using the first reference potential, the second reference potential, the first voltage value, and the second voltage value as described above is also expressed as "measuring" the voltage of the electric wire.

[0008] The measurement voltage calculation unit may be configured to calculate the measurement value by a least squares method, thereby reducing the load on a device related to calculations without performing complex calculations.

[0009] The measured voltage calculation unit may be configured to calculate the measured value by the following formula:

number

[0010] The first and second reference potentials may be out of phase with each other by 180 degrees and have the same absolute value. This simplifies the calculation for measuring the voltage value and reduces the load on the device involved in the calculation.

[0011] The reference potential output source may be configured to output the first reference potential and the second reference potential at a frequency different from the frequency of the AC power supply. For example, by configuring the reference potential output source to output an AC voltage at a frequency different from the frequency of the AC power supply by about 1 Hz to 5 Hz, it is possible to output a plurality of potentials having different differences from the detected potential of the electric wire in a time series. Among the plurality of potentials, values ​​that are 180 degrees out of phase with each other and have the same absolute value can be used as the first reference potential and the second reference potential.

[0012] Moreover, the first reference potential and the second reference potential may be lower than the output voltage of the AC power supply. By setting the reference potentials to low values ​​in this manner, the load on the device can be reduced and safety can be increased.

[0013] The power meter further includes a correction value calculation unit that calculates a correction value for the detected potential based on the measured value calculated by the measured voltage calculation unit and the detected potential. The device may further include a wire voltage determination unit that determines, as the value of the voltage of the wire, either the measurement value calculated by the measurement voltage calculation unit or a value obtained by correcting the detected potential using the correction value.

[0014] By calculating the correction value as described above and calibrating the detected potential with the correction value to obtain the voltage value of the electric wire, the voltage value of the electric wire can be obtained more quickly than by constantly measuring it using a measured voltage calculation unit. This reduces the load on the device related to calculations and also makes it possible to detect so-called momentary sags.

[0015] Moreover, the measurement voltage calculation unit calculates the measurement value when a preset trigger condition is satisfied, the correction value calculation unit calculates the correction value when the trigger condition is satisfied; The electric wire voltage determination unit determines, when the measured value is calculated, the measured value as the value of the voltage of the electric wire, and, when the trigger condition is not satisfied, determines a value obtained by correcting the detected potential using the most recently calculated correction value as the value of the voltage of the electric wire. The device may be configured to:

[0016] Even if the correction value is calculated once, the capacitance of the wire coating gradually changes due to factors such as the temperature characteristics, humidity characteristics, and changes over time, and the accuracy of the voltage measurement value decreases accordingly. In this regard, with the above-described configuration, the correction value is recalculated when a predetermined trigger condition is satisfied, so that the effect of changes in the coating capacitance can be suppressed and good measurement accuracy can be maintained even after the voltmeter is installed and time has passed.

[0017] The present invention also provides a method for producing a semiconductor device comprising the steps of: A voltage measurement method for non-contact measurement of a voltage of an insulated electric wire connected to an AC power source, comprising: acquiring a first voltage value which is a potential difference between a detected potential detected from the electric wire and a first reference potential; acquiring a second voltage value that is a potential difference between a detection potential detected from the electric wire and a second reference potential; calculating a voltage measurement of the electric wire using at least the first reference potential, the second reference potential, the first voltage value, and the second voltage value; Equipped It can also be considered as a voltage measurement method.

[0018] The present invention also provides a method for producing a semiconductor device comprising the steps of: 1. A computing device for measuring a voltage of an electric wire, the computing device being used together with a voltage detection electrode that is connected to an AC power source and detects a potential of the electric wire from an outside of the insulating coating of the electric wire, the computing device comprising: outputting at least a first reference potential and a second reference potential, the values ​​of which are set in advance; acquiring a first voltage value that is a potential difference between a detected potential detected from the electric wire and the first reference potential; acquiring a second voltage value that is a potential difference between the detected potential detected from the electric wire and the second reference potential; configured to calculate a measurement of the voltage of the electric wire using at least the first reference potential, the second reference potential, the first voltage value, and the second voltage value. It can also be considered as a computing device.

[0019] The present invention can also be applied to the following wattmeters in combination with a current sensor: A power meter for measuring power consumption of a load connected to an AC power source, comprising: a current sensor connected to the AC power source and configured to detect a current in the insulated electric wire from outside the insulating coating of the electric wire; a voltage detection electrode for detecting a potential of the electric wire from outside the insulating coating; a reference potential output source that outputs at least a first reference potential and a second reference potential; a voltage value output unit that outputs a first voltage value, which is a potential difference between the detection potential output from at least the voltage detection electrode and the first reference potential, and a second voltage value, which is a potential difference between the detection potential and the second reference potential; a measurement voltage calculation unit that calculates a measurement value of the voltage of the electric wire using at least the first reference potential, the second reference potential, the first voltage value, and the second voltage value; a power consumption calculation unit that calculates the power consumption of the load based on the value of the current detected by the current sensor and the value of the voltage calculated by the measured voltage calculation unit; Equipped It is a power meter. Effect of the Invention

[0020] According to the present invention, it is possible to provide a technique that enables the voltage of an electric wire connected to an AC power source to be accurately measured from outside the insulating coating without being affected by the thickness of the insulating coating. [Brief description of the drawings]

[0021] [Figure 1] Fig. 1A is a schematic diagram showing a voltmeter according to an application example of the present invention and an electric wire to be measured, and Fig. 1B is an explanatory diagram showing the concept of a voltage measurement method using the voltmeter according to this application example. [Diagram 2] FIG. 2 is a flowchart showing a process flow for determining a voltage value of an electric wire using a voltmeter according to an application example of the present invention. [Diagram 3] Fig. 3A is a schematic diagram showing an outline of the external appearance of the voltmeter according to embodiment 1. Fig. 3B is a block diagram showing the functional configuration of the voltmeter according to embodiment 1. [Figure 4] Fig. 4A is a first diagram showing the appearance of the sensor head according to embodiment 1. Fig. 4B is a second diagram showing the appearance of the sensor head according to embodiment 1. Fig. 4C is a third diagram showing the appearance of the sensor head according to embodiment 1. [Diagram 5] FIG. 5 is an exploded view illustrating each element constituting the sensor head according to the first embodiment. [Figure 6] Fig. 6A is a first cross-sectional view showing the internal configuration of the sensor head according to embodiment 1. Fig. 6B is a second cross-sectional view showing the internal configuration of the sensor head according to embodiment 1. [Figure 7]FIG. 7 is an explanatory diagram illustrating the operational amplifier circuit according to the first embodiment. [Figure 8] FIG. 8 is a cross-sectional view showing an outline of a cross section of the cable according to the first embodiment. [Figure 9] FIG. 9 is a diagram illustrating an example of a waveform of a signal output from the differential amplifier according to the first embodiment. [Figure 10] FIG. 10 is a block diagram illustrating a process performed by the measured voltage calculation unit according to the first embodiment. [Figure 11] FIG. 11 is a diagram illustrating an operational amplifier circuit according to a first modification of the first embodiment. [Figure 12] FIG. 12 is a first explanatory diagram showing the relationship between the waveform of the output signal of the differential amplifier according to the second modification of the first embodiment and the reference potential. [Figure 13] FIG. 13 is a second explanatory diagram showing the relationship between the waveform of the output signal of the differential amplifier according to the second modification of the first embodiment and the reference potential. [Figure 14] FIG. 14 is an explanatory diagram showing an image of a case where a voltage of a three-phase AC is measured in the third modified example of the first embodiment. [Figure 15] Fig. 15A is a schematic diagram showing an outline of the external appearance of a voltmeter according to embodiment 2. Fig. 15B is a block diagram showing the functional configuration of the voltmeter according to embodiment 2. [Figure 16] FIG. 16 is a block diagram illustrating the processes performed by the measured voltage calculation unit, the correction value calculation unit, the detected potential correction unit, and the wire voltage determination unit according to the second embodiment. [Figure 17] Fig. 17A is a schematic diagram showing an outline of the external appearance of the power sensor according to embodiment 3. Fig. 17B is a block diagram showing the functional configuration of the power sensor according to embodiment 3. [Figure 18] FIG. 18 is a cross-sectional view showing a schematic cross section of a cable connecting the first sensor head and the main body according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. Note that the configurations of the following embodiments are merely examples, and the present invention is not limited to the configurations of these embodiments.

[0023] <Application Examples> 1A and 1B are explanatory diagrams for explaining an example of application of the present invention. X from the outside of the insulating coating 992 (i.e., non-contact 1A is a schematic diagram showing an electric wire 911 covered with an insulating coating 992, and a voltmeter 9 installed on the electric wire via the insulating coating 992. As shown in FIG. 1A, the voltmeter 9 includes a voltage detection electrode 993 arranged on the outside of the insulating coating 992, a reference potential output source 994 that outputs a plurality of different reference potentials, a voltage value output unit 995, and a measured voltage calculation unit 996.

[0024] The voltage detection electrode 993 detects the potential of the electric wire 991 from the outside of the insulating coating 992. The insulating coating 992 functions as a capacitor, and its capacitance C X The reference potential output source 994 outputs at least a first reference potential and a second reference potential, each of which has a different value.

[0025] Furthermore, the voltage value output unit 995 outputs a first voltage value, which is the potential difference between the detected potential output from the voltage detection electrode 993 and the first reference potential, and a second voltage value, which is the potential difference between the detected potential and the second reference potential. Furthermore, the measured voltage calculation unit 996 calculates the measured value of the voltage of the electric wire 991 using the first reference potential, the second reference potential, the first voltage value, and the second voltage value. As described above, when the potential of the electric wire 991 is detected via the insulating coating 992, its capacitance C X Therefore, the potential detected by the voltage detection electrode 993 does not represent the accurate voltage value of the electric wire 911.

[0026] In this regard, a known prior art technique is to measure the voltage of the electric wire 911 in advance by a contact method and use the obtained measurement value to calibrate the value detected by a non-contact method. However, if the thickness (or other characteristics) of the wire insulation changes due to factors such as time, which causes a change in the capacitance of the insulation, the voltage cannot be measured correctly using the above-mentioned prior art.

[0027] In contrast, the voltmeter 9 according to this application example uses a plurality of different reference potentials and potential differences between the respective reference potentials and the detection potential to measure the potential of the electric wire 991 regardless of the capacitance of the insulating coating 992. Fig. 1B is an explanatory diagram showing the concept of a voltage measurement method using the voltmeter 9 according to this application example.

[0028] In FIG. 1B, V1 and V2 respectively indicate the first reference potential and the second reference potential on the Y axis (electric potential). O1 , V O2 indicate the first voltage value and the second voltage value on the X-axis (the output value of the voltage value output unit) corresponding to the first reference potential and the second reference potential, respectively. X indicates the voltage value of electric wire 911. The dashed line in the figure indicates a line that linearly approximates the output value of voltage value output unit 995 when the capacitance of insulating coating 992 is large (specifically, the difference between the output of voltage detection electrode 993 and the reference potential), and the dashed line indicates the case when the capacitance of insulating coating 992 is small.

[0029] As shown in FIG. 1B, the first voltage value V O1 , the second voltage value V O2 However, the first voltage value V O1 , the second voltage value V O2 1B where both are 0, the voltage of the electric wire 991 can be accurately measured regardless of the capacitance of the insulating coating 992. X can be sought.

[0030]

number

[0031] In the above formula 1, the first reference potential V1 and the second reference potential V2 output from the reference potential output source 994 are set to potentials having the same absolute value but a phase difference of 180 degrees (i.e., opposite signs). By using the potential as the voltage, the voltage value V of the electric wire 911 can be calculated more simply. X That is, since V2 = -1 × V1, the voltage value V of the electric wire 911 can be calculated by the following formula 2. X can be sought.

[0032]

number

[0033] FIG. 2 shows the voltage value V of the wire measured using a voltmeter 9. X This is a flowchart showing the process flow for determining the voltage value V X The flow of the process for obtaining the first voltage value V is as follows: the first reference voltage V1 is output from the reference voltage output source 994 (S101), and the first voltage value V O1 Furthermore, a second reference potential V2 is output from the reference potential output source 994 (S103), and a second voltage value V O2 Then, the first reference potential V1, the second reference potential V2, and the first voltage value V O1 , the second voltage value V O2 (for example, by using the above formula 1 or 2), the voltage value of the electric wire V X is calculated (S105).

[0034] As a result, when measuring the voltage of the electric wire 911 in a non-contact manner via the insulating coating 992, the voltage of the electric wire 911 can be measured with high accuracy even if the magnitude of the capacitance of the insulating coating 992 changes.

[0035] <Embodiment 1> (Device Overview) Next, an example of an embodiment of the present invention will be described in more detail. Fig. 3A is a schematic diagram showing an outline of a voltmeter 1 according to this embodiment. Fig. 3B is a block diagram showing a functional configuration of the voltmeter 1. The voltmeter 1 according to this embodiment includes two sensor heads that are installed so as to cover an electric wire from above the wire's insulation as described below, and is configured to be able to measure, in a non-contact manner, a (line-to-line) voltage in an electric wire of, for example, a single-phase two-wire power distribution system.

[0036] 3A, the voltmeter 1 has a cubic main body 10 and a sensor head 20a, 20b provided at the tip of each of two cables extending from the main body 10. In the following, when there is no need to distinguish between the sensor head 20a and the sensor head 20b, such as when describing matters common to both, the sensor heads will be referred to as sensor head 20. The sensor head and the cable will also be collectively referred to as a "measurement probe."

[0037] As shown in Fig. 3B, the sensor head 20a and the sensor head 20b are included in a sensor unit 200 as a functional unit. The sensor head 20a includes a first potential detection unit 201 including an operational amplifier circuit (not shown in Fig. 3B) described later, and the sensor head 20b similarly includes a second potential detection unit 202. Furthermore, by attaching each sensor head to an electric wire connected to an AC power source through its insulation, the potential of the electric wire is detected and the signal is output to the main unit 10. This makes it possible to measure the line voltage of a single-phase AC (two-wire system).

[0038] The main body 10 also includes functional units, such as an A / D (Analog-to-Digital) converter 12, a D / A (Digital-to-Analog) converter 13, a memory unit 14, a power supply unit 15, a communication unit 16, a display unit 17, and a control unit 100. The analog signal output from the sensor head 20b is converted into a digital signal by the A / D conversion unit 12 and input to the control unit 100. The control unit 100 processes the input signal to measure the voltage value of the electric wire on which each sensor head 20 is installed.

[0039] (Main body configuration) The following is a further description of the configuration of the main body 10. The main body 10 is configured such that a circuit board (not shown) is housed in a cubic housing, and one end of a cable is connected to the sensor head 20, and the other end of the cable is connected to the circuit board.

[0040] The A / D conversion unit 12 converts the analog signal input from the sensor head 20 into a digital signal and outputs it to the control unit 100. In addition, the D / A conversion unit 13 converts the digital value of a reference potential generated by a reference potential generation unit 101 (described later) into an analog signal and outputs it to each sensor head 20.

[0041] The storage unit 14 includes a main storage device (not shown), such as a RAM (Random Access Memory) or a ROM (Read Only Memory), and an auxiliary storage device (not shown), such as a removable SD (Secure Digital) memory card. The main storage device is a storage medium that stores programs executed by the control unit 100 and operation setting information. The auxiliary storage device stores data such as the effective values ​​of the measured voltages, information related to the times when these data were obtained, and predetermined setting values ​​set for voltage measurement.

[0042] The power supply unit 15 is a power source for the entire voltmeter 1 including the main body 10 and the sensor head 20, and may be, for example, a removable storage battery. Alternatively, the power supply unit 15 may be connected to a PoE (Power over Ethernet) hub via a LAN (Local Area Network) cable.

[0043] The communication unit 16 includes an antenna (not shown) for wireless communication, and has a function of communicating with other devices such as an information processing terminal by at least BLE (Bluetooth (registered trademark) Low Energy) communication. It may also include a terminal for wired communication. When performing wired communication, it may be connected to a PoE hub, for example, and receive power supply via a LAN cable.

[0044] In this embodiment, an external information processing terminal connected via the communication unit 16 plays the role of an input / output I / F (interface). That is, the measured voltage value measured by the voltmeter 1, the current setting value related to the operation of the voltmeter 1, and the like are transmitted from the communication unit 16, and these pieces of information can be referred to via an external information processing terminal (e.g., a notebook PC, a smartphone, etc.). The setting of the voltmeter 1 is also performed by receiving information inputted at the information processing terminal by the communication unit 16. Furthermore, data such as measured values ​​stored in the storage unit 14 may be transmitted to a server device (not shown). In this case, the timing of transmission can be, for example, automatically transmitting data at a predetermined time or at a predetermined time interval, automatically transmitting data when a predetermined amount of data or more is accumulated, or transmitting data upon receiving a data transmission request from the server.

[0045] In this way, the voltmeter 1 according to this embodiment does not have a configuration for directly receiving input and a configuration for outputting information in a perceptible manner, which allows the main body 10 to be simplified (reduced in cost) and made smaller, and also allows the power consumption for these components to be saved, thereby extending the life of the storage battery.

[0046] The control unit 100 is, for example, a CPU (Central Processing Unit) etc. The control unit 100 measures (calculates) the voltage of the electric wire using a signal input from the sensor head 20 in accordance with a predetermined program. It also controls the entire voltmeter 1, such as transmitting and receiving information to and from external devices via the communication unit 16. The predetermined program is stored in the memory unit 14 and is read out from there. The control unit 100 also includes, as functional modules, a reference potential generating unit 101, a measured voltage calculating unit 102, and a line voltage calculating unit 103. Each of these functional modules will be described in detail later.

[0047] (Sensor head structure) The structure of the sensor head 20 will be described in more detail below. Figures 4A to 4C are diagrams showing the external appearance of the sensor head 20. The sensor head 20 has a generally hollow cylindrical appearance, and is formed by assembling a plurality of components described below to a base portion 21 constituted by two resin base members 21a and 21b. The base portion 21 is formed so as to be freely deformed between a hollow cylindrical state as shown in Figure 4A (hereinafter referred to as a closed state) and a state in which two arch-shaped structures are adjacent to each other as shown in Figures 4B and 4C (hereinafter referred to as an open state) by pivotally supporting the base members 21a and 21b at two hinge portions 29 provided at both ends of the cylinder in the axial direction at one point on the circumference of the cylinder.

[0048] The sensor head 20 is adapted to open and close at a location on the opposite side of the circumference to the hinge portion 29, and is configured to be lockable in a closed state by fitting a convex portion 211 provided on one of the base members 21a and 21b into a concave portion (not shown) provided at a corresponding position on the other of the base members 21a and 21b at both axial ends of the cylinder at the location, thereby allowing the sensor head 20 to be locked in a closed state. When the sensor head 20 is in a closed state, the convex portion 211 and the concave portion are released by applying a force to pull apart the locked portions of the base members 21a and 21b, and the sensor head 20 can be opened. When the sensor head 20 is attached to an electric wire, the sensor head 20 is opened and the covered electric wire is sandwiched between the arch-shaped recesses of the base members 21a and 21b, and the sensor head 20 is closed, whereby the covered electric wire is inserted into the hollow portion of the cylinder and locked, completing the attachment of the sensor head 20.

[0049] Next, a description will be given of the internal structure of the sensor head 20. Fig. 5 is an exploded view illustrating each element constituting the sensor head 20. Fig. 6A is a cross-sectional view of the sensor head 20 taken along the dashed line in Fig. 4A, and Fig. 6B is a cross-sectional view of the sensor head 20 taken along the dashed line in Fig. 4B.

[0050] As shown in Figures 5, 6A, and 6B, the sensor head 20 is composed of the following components: a base portion 21, a potential detection electrode 22, an FPC (Flexible Printed Circuits) 23, an operational amplifier circuit 24, an electric field shield 25, an insulating seal 26, a magnetic field shield 27, and a cover member 28.

[0051] As described above, base portion 21 is formed by connecting base members 21a and 21b with hinge portion 29, and as shown in FIG. 5, the outer circumferential side of the cylinder is recessed in stages toward the axial center, and the most recessed portion at the axial center has a shape resembling a square prism (with a circular hollow interior).

[0052] The potential detection electrode 22 is formed of, for example, copper foil, and is a member for detecting a potential generated by electrostatic induction according to the voltage of a connected electric wire. The FPC 23 is a typical flexible printed circuit board having a structure in which a conductor foil is attached to a thin-film insulator via an adhesive layer. The potential detection electrode 22 is provided on the back side of the FPC 23 (i.e., the side closer to the base portion 21). The operational amplifier circuit 24 is a circuit formed on the FPC 23 and includes a plurality of operational amplifiers. The operational amplifier circuit 24 will be described later.

[0053] The FPC 23 is adhered and fixed to the base part 21 by wrapping it around a rectangular prism. More specifically, the surface on which the potential detection electrode 22 is provided is adhered to the base part 21 so that both ends of the FPC 23 in the longitudinal direction are positioned at the opening / closing positions (corresponding to one of the corners of the rectangle) of the base part 21 (i.e., not positioned at a corner that is not in the opening / closing position or on any side). The opening / closing position of the base part 21 corresponds to the lower corner of the diamond in the center of Fig. 6A. Although not shown, one end of a cable (electric wires inside) is connected to the FPC 23, and signals are transmitted and received to and from the main body part 10 via the cable.

[0054] The electric field shield 25 is a member made of a non-magnetic metal, and is wrapped around the FPC 23 to block the influence of an external electric field. The insulating seal 26 is a sealing member made of an insulating material. The magnetic field shield 27 is a member made of a magnetic material such as iron or ferrite. The cover member 28 is made of the same resin as the base members 21a and 21b, for example, and serves as an exterior for the central portion of the sensor head 20 in the axial direction.

[0055] The magnetic field shield 27 and the cover member 28 are each a pair of two arch-shaped members that are bonded and fixed to the base portion 21 with an adhesive such as double-sided tape. At this time, the magnetic field shield 27 and the cover member 28 are positioned so that a gap G is formed on the axis on which the hinge portion 29 is provided.

[0056] If the gap G is not formed, interference will occur at a location located outside the rotation axis of the hinge portion 29 when the base portion 21 is in the open state. For this reason, the gap G is necessary, but the internal components will be exposed at the gap G. Since it is expected that bus bars without insulating coating will be used in some places inside the control panel in which the sensor head 20 is installed, there is a risk of accidents such as electric shock if the exposed parts come into contact with the bus bars. For this reason, by attaching an insulating sticker 26 so as to fill the gap G as shown in FIG. 6A, such accidents can be prevented.

[0057] Next, the operational amplifier circuit 24 will be described. Fig. 7 is an explanatory diagram for explaining the operational amplifier circuit according to this embodiment. As shown in Fig. 7, the operational amplifier circuit 24 according to this embodiment includes a reference potential amplifier 241, a potential detection amplifier 242, and a differential amplifier 243.

[0058] The reference potential amplifier 241 receives the reference potential generated by the reference potential generating unit 101 of the main body 10 and output via the D / A conversion unit 13 and GND (reference potential of the entire circuit) as input signals, and amplifies and outputs the reference potential.

[0059] The potential detection amplifier 242 detects the output signal from the reference potential amplifier 241 and the output from the potential detection electrode 22 (the capacitance C X The potential detection amplifier 242 amplifies and outputs the potential from the potential detection electrode 22 using the detection potential (detected potential influenced by the potential detection electrode 22) as an input signal. In this embodiment, the output of the potential detection amplifier 242 and the element at the inverting input (-) terminal are connected to a capacitor C f The voltage is amplified as a capacitor. A capacitor has infinite impedance for DC, but if the impedance between the op-amp output and the - terminal is infinite, it will not be stable. Therefore, a high resistance for DC bias is used as the capacitor C f It is provided in parallel with.

[0060] The differential amplifier 243 receives the output signal of the reference potential amplifier 241 and the output signal of the potential detection amplifier 242 as input signals, amplifies the difference between them (potential difference), and outputs the amplified signal. The output signal from the differential amplifier 243 is transmitted to the main body 10, converted into a digital signal by the A / D conversion unit 12, and input to the control unit 100.

[0061] In addition, a current flows between different potentials such as the negative terminal of the potential detection amplifier 242 and the ground (not shown). The current is C f Since the electric potential is supplied from the output terminal of the potential detection amplifier 242 through the GND, the output of the potential detection amplifier 242 changes. For this reason, in this embodiment, the electric field shield 25 is connected to the reference potential, and the operational amplifier circuit 24 is covered with a shield of the reference potential that has the same potential as the - terminal of the potential detection amplifier 242, thereby eliminating the current that flows from the - terminal of the potential detection amplifier 242 to the outside of the circuit. Furthermore, in this embodiment, further shielding is provided by setting the magnetic field shield 27 to the same potential as GND (for example, 0 V) ​​so that the reference potential is not affected from the outside.

[0062] Such shielding is also applied to the cable. Fig. 8 is a cross-sectional view showing an outline of the cable cross section. As shown in Fig. 8, a voltage sensor electric wire covered with a voltage sensor electric wire sheath 35 is disposed inside the cable according to this embodiment. The voltage sensor electric wire includes a signal line 31, an op-amp positive power supply line 32 which is an electric wire for the positive power supply (e.g., 18 V) of the op-amp, and an op-amp negative power supply line 33 which is an electric wire for the negative power supply (e.g., -18 V) of the op-amp, and these are shielded by a reference potential shield 34. Furthermore, a 0V shield 36 is provided inside the cable sheath 37, and the cable is shielded in the same manner as the op-amp circuit 24.

[0063] (Function module of the control unit) Next, each functional module of the control unit 100 will be described. The reference potential generating unit 101 generates and outputs an AC voltage whose value is lower than that of the commercial power supply (for example, about 10%) and whose frequency differs slightly from that of the commercial power supply (for example, about 1 Hz to 5 Hz). That is, the reference potential generating unit 101 outputs a plurality of reference potentials that differ according to the difference in phase.

[0064] The measured voltage calculation unit 102 calculates the voltage value of the electric wire to be measured based on the output signal of the differential amplifier 243 and the reference potential. A specific method for doing this will be described with reference to FIG. 7. X The capacitance of the wire insulation is C X The capacitance of the capacitor of the potential detection amplifier 242 is C f The output signal of the differential amplifier 243 is V O and the reference potential is V REF Then, the following equation 3 holds.

[0065]

number

[0066] That is, the reference potential is V REF1 The output signal of the differential amplifier 243 at V O1 and the reference potential is V REF2 The output signal of the differential amplifier 243 at V O2 Then, we have the following Equations 4 and 5, respectively.

[0067]

number

[0068]

number

[0069] From the formulas 4 and 5, the formula 1 explained in the application example is established (V of the formulas 4 and 5) REF1 is V1 in Equation 1, and V REF2corresponds to V2 in Equation 1). That is, the capacitance of the wire insulation, C X (And the capacitor C f ) Regardless of the voltage V of the wire to be measured, based on the output signal of the differential amplifier 243 and the reference potential, X It becomes possible to calculate

[0070] If the phase and frequency of the electric wire to be measured can be detected at all times, the first reference potential and the second reference potential can be generated and output accordingly, but this is usually difficult. For this reason, in this embodiment, the reference potential generating unit 101 outputs an AC voltage at a frequency slightly shifted from the frequency of the voltage (power supply voltage) of the electric wire to be measured. Here, the frequency of the power supply voltage is 60 Hz, and the frequency of the signal output by the reference potential generating unit 101 is 61 Hz. Since there is a frequency of 1 Hz, the phases of the electric wire potential and the reference potential match (in-phase) and are inverted (out-of-phase) every 0.5 seconds, and large and small peaks appear in the output of the differential amplifier 243 accordingly. FIG. 9 shows the waveform (sine wave) of the output signal from the differential amplifier 243.

[0071] Here, when the output signal of differential amplifier 243 is at the maximum value and at the minimum value, the reference potential has the same absolute value with a phase shift of 180 degrees (determined by the sign), so the following equation 6 holds from equation 2 described in the application example.

[0072]

number

[0073] In addition, in Equation 6, V peak is the maximum effective value of the output signal of the differential amplifier 243, V bottom is also the minimum effective value, V REF indicates the reference potential.

[0074] In this embodiment, the measured voltage calculation unit 102 calculates the voltage value V XFIG. 10 shows a block diagram of the process performed by the measured voltage calculation unit 102. As shown in FIG. 10, the measured voltage calculation unit 102 calculates the root mean square (effective value) of the signal constantly input from the differential amplifier 243, and holds (peak hold, bottom hold) the maximum and minimum values ​​during the sampling period until the end of the next sampling period. Then, the obtained maximum value (V peak ) and minimum value (V bottom ) and the reference potential (V REF ) and calculate the voltage value V X The sampling period may be determined by receiving an appropriate timing signal.

[0075] The line voltage calculation unit 103 calculates the line voltage values ​​V X From this, the line voltage of the electric wires connected to the single-phase two-wire AC power supply is calculated. That is, the line voltage of the two electric wires connected to the single-phase AC power supply (the voltage of the single-phase AC power supply) is measured by calculating the difference between the voltage value measured by the signal from sensor head 20a and the voltage value measured by the signal from sensor head 20b.

[0076] The voltmeter 1 configured as described above has an extremely simple and safe configuration, and can measure AC voltage in a non-contact manner without being affected by differences in capacitance due to the thickness of the wire coating, etc. In other words, there is no need to use a high-voltage reference potential, perform extensive calculation processing, or provide switches to switch between multiple capacitors in order to reduce the effect of the capacitance of the wire coating. In addition, there is no need to perform correction work according to the installation conditions of the voltmeter before starting measurement, and measurement can be started simply by attaching the measurement probe. This can be done.

[0077] (Variation 1) In the first embodiment, the potential detection amplifier 242 of the operational amplifier circuit 24 uses a capacitor to amplify the detection signal, but this is not necessarily the case. Fig. 11 shows a modified example of the potential detection amplifier 244. As shown in Fig. 11, in this modified example, a resistor R is used as an element between the output and the - terminal of the potential detection amplifier 244 to amplify the detection signal. f Therefore, DC bias is not a problem.

[0078] In this modified example, the voltage value of the electric wire to be measured is V X The capacitance of the wire insulation is C X The resistance of the potential detection amplifier 244 is R f The output signal of the differential amplifier 243 is V O and the reference potential is V REF Then, the following equation 7 holds: where ω is the angular frequency (rad / sec).

number

[0079] Also, the reference potential is V REF1 The output signal of the differential amplifier 243 at V O1 and the reference potential is V REF2 The output signal of the differential amplifier 243 at V O2 Then, we have the following Equations 8 and 9, respectively.

[0080]

number

[0081]

number

[0082] From equations 8 and 9, the above equation 1 holds (V REF1 is V1 in Equation 1, and V REF2 corresponds to V2 in Equation 1). That is, the capacitance of the wire insulation, C XRegardless of the voltage V of the wire to be measured, the voltage V of the wire to be measured is calculated based on the output signal of the differential amplifier 243 and the reference potential. X It becomes possible to calculate

[0083] In this modified example, there is no need to use a high resistance (for example, the capacitance of the coating C X If is 5pF, R f The input bias current of the op-amp is about 1 MΩ, so there is no need to select an op-amp with an extremely small input bias current. f A capacitor may be provided in parallel with the resistor R1, and in that case the capacitance of the capacitor may be about 1 to 100 pF. In other words, since there is a large degree of freedom in the selection of the capacitor, the cost of the device can be reduced by using a general-purpose (cheap and easily available) operational amplifier.

[0084] (Variation 2) In the above-mentioned embodiment 1, the measured voltage calculation unit 102 calculates the voltage value of the electric wire using two reference potentials, the potential when the output of the differential amplifier 243 is maximum and the potential when the output is minimum, but the voltage value of the electric wire may be calculated using more reference potentials. Such a modified example will be described with reference to Figs. 12 and 13. In the following, the output of the differential amplifier 243 is also referred to as a differential voltage value.

[0085] FIG. 12 shows the waveform (sine wave) of the output signal of the differential amplifier 243 and the reference potential V REF1 ~V REF5 FIG. 12 is an explanatory diagram showing the relationship between V REF1 is the difference The reference potential at which the dynamic voltage is maximum is V REF5 is the reference potential at which the differential voltage is at a minimum. Here, V REF1 and V REF5 are the same absolute value but shifted 180 degrees in phase (with the sign reversed), so V REF5 =-V REF1 And V REF1 and V REF5 V, which is the center of REF3 is 0. Also, V REF1and V REF3 V, which is the center of REF2 is 1 / √2V REF1 , V REF3 and V REF5 V, which is the center of REF4 is -1 / √2V REF1 That is, V REF1 and V REF5 Once is specified, three more reference potentials and their corresponding differential voltage values ​​can be obtained.

[0086] FIG. 13 is an explanatory diagram showing the concept of the distribution of five reference potentials and their corresponding differential voltage values. The meanings of the X-axis and Y-axis of the graph in FIG. 13 as well as the dashed and dashed lines are the same as those in FIG. 1B. REF1 ~V REF5 indicates the reference potential on the Y axis (electric potential), and V O1 ~V O5 indicates the value of the differential voltage value corresponding to each reference potential.

[0087] In this way, when there are three or more parameters used to calculate the voltage value of the electric wire, the measured voltage calculation unit 102 calculates the voltage value V of the electric wire by using a linear approximation such as the least squares method. X Specifically, the measured voltage calculation unit 102 calculates the voltage value V of the electric wire by the following formula 10. X In addition, in Equation 10, V REFi is the reference potential, V oi indicates the differential voltage value.

[0088]

number

[0089] By doing the above, it is possible to calculate the voltage value V of the electric wire more accurately by using more reference potentials and differential voltage parameters. X can be sought.

[0090] (Variation 3) The voltmeter 1 according to the above embodiment has two sensor heads 20 and is configured to be capable of measuring the line voltage of a single-phase (two-wire) AC, but it is also possible to add a sensor head to make the voltmeter capable of measuring the voltage of each phase of a three-phase AC (three-wire). Fig. 14 shows an explanatory diagram for explaining such a modified example. Fig. 14 shows a schematic circuit of three-phase AC having R, S, and T phases and a state in which the sensor heads of the voltmeter are installed on the electric wires of each phase.

[0091] In Figure 14, V R , V S , V T indicates the respective phase voltages, and O1, O2, and O3 indicate differential voltage values ​​output from the differential amplifier 243 of each sensor head. The measured voltage calculation unit 102 according to this modification calculates the measured voltage value obtained using a plurality of O1s, the measured voltage value obtained using a plurality of O2s, and the measured voltage value obtained using a plurality of O3s, by any of the methods described above. Then, the line voltage calculation unit 103 according to this modification calculates V R Similarly, V is calculated by subtracting the voltage measured using O2 from the voltage measured using O3. S and subtract the voltage measured using O1 from the voltage measured using O2 to obtain V T In this way, the voltage of each phase of the AC in a three-phase, three-wire system can be calculated.

[0092] <Embodiment 2> A second embodiment of the present invention will be described below. The voltmeter 2 has many components in common with the voltmeter 1 according to the first embodiment. Therefore, in this embodiment, the same components and processes as those in the first embodiment are denoted by the same reference numerals, and a repeated description will be omitted.

[0093] FIG. 15A is a schematic diagram showing an outline of the voltmeter 2 according to this embodiment. FIG. 15B is a block diagram showing the functional configuration of the voltmeter 2. As shown in FIGS. 15A and 15B, the voltmeter 2 according to this embodiment has a main body 11 that is slightly different from that of the voltmeter 1 of embodiment 1, and is generally similar in configuration to the voltmeter 1 of embodiment 1. Specifically, the voltmeter 2 according to this embodiment is different from the voltmeter 1 of embodiment 1 in that the main body has a display unit 17 and a reference signal selection unit 18 as functional configurations, and further has a correction value calculation unit 111, a detected potential correction unit 112, and a wire voltage determination unit 113 as functional modules of the control unit 110.

[0094] In the voltmeter 2 of this embodiment, the configuration of the sensor head 20 is the same as that of the voltmeter 1 of embodiment 1, and it is installed on the electric wire to be measured through its insulating coating, and detects the electric potential of the electric wire using the potential detection electrode 22 and the operational amplifier circuit 24, and outputs the potential to the main body 11.

[0095] The display unit 17 is a light emitting diode (LED) (not shown in FIG. 15A). The meter includes a display means such as a diode, liquid crystal, or organic EL (Electro Luminescence), and displays various information such as a measured value. The measured value and other information may be displayed by numbers, or may be displayed in a form such as a bar graph meter. When using such a meter, for example, when a measured value deviates from the rated value of the commercial power supply, the measured value may be displayed in a color-coded manner according to a threshold value so that the measured value can be instantly recognized. For example, when the commercial power supply is 100V, a measured value below 90V or above 110V is regarded as an abnormal output, and 95V and 105V are set as alarm thresholds before the abnormal output. Then, when the measured value is in the range of 95V to 105V, a green bar is displayed as a normal output, and when an abnormal output is displayed, a red bar is displayed, and the range between the normal output and the abnormal output is displayed with a yellow bar. The display means is not limited to this, and an analog needle meter may be adopted.

[0096] The reference signal selection unit 18 selects whether the reference potential to be input to the operational amplifier circuit 24 of the sensor unit 200 is the potential generated by the reference potential generation unit 101 and output via the D / A conversion unit 13, or a fixed potential of a predetermined value. Specifically, when a predetermined trigger condition is satisfied, the potential input via the D / A conversion unit 13 is selected, and when the trigger condition is not satisfied, the fixed potential is selected. Here, the fixed potential may be a potential applied from a power source, or may be a GND potential, etc. The trigger condition will be described later.

[0097] The correction value calculation unit 111 calculates a correction value for the detected potential based on the measured value of the electric wire calculated by the measured voltage calculation unit 102 and the detected potential output by the potential detection amplifier 242. Specifically, for example, a ratio between the detected potential output by the potential detection amplifier 242 and the measured value of the electric wire calculated by the measured voltage calculation unit 102 using the detected potential is calculated, and this ratio can be used as the correction value. The correction value calculated by the correction value calculation unit 111 is stored in the memory unit 14.

[0098] The detected potential correction unit 112 corrects the detected potential output by the potential detection amplifier 242 and amplified by the differential amplifier 243 when a predetermined fixed potential is input to the reference potential amplifier 241, based on the correction value calculated by the correction value calculation unit 111. That is, the correction is performed by multiplying the detected potential by the correction value, thereby obtaining a highly accurate voltage regardless of the capacitance of the wire coating. Calculate the value.

[0099] Wire voltage determination unit 113 determines, as the voltage value of the wire, either the value calculated by measured voltage calculation unit 102 or the value obtained by correcting the detected potential by detected potential correction unit 112. Specifically, if a trigger condition described below is satisfied, the value calculated by measured voltage calculation unit 102 is determined as the voltage value of the wire, and if the trigger condition is not satisfied, the value obtained by correcting the detected potential by detected potential correction unit 112 is determined as the voltage value of the wire.

[0100] 16 is a block diagram showing the flow of processing by control unit 110 (measured voltage calculation unit 102, correction value calculation unit 111, detected potential correction unit 112, and wire voltage determination unit 113) of a signal input from sensor unit 200 to A / D conversion unit 12 in voltmeter 2 according to this embodiment. Note that a "switching" block in FIG. 16 switches between whether or not to calculate a voltage value by measured voltage calculation unit 102 and whether or not to calculate a correction value by correction value calculation unit 111, depending on whether a predetermined trigger is satisfied.

[0101] As described in the description of the first embodiment, the signal generated by the reference potential generating unit 101 is an AC signal with a frequency slightly different from that of the commercial power supply, and therefore it takes time to detect the peak and bottom of the differential voltage value. For example, if the frequency difference is 1 Hz, it takes more than one second to obtain the peak and bottom values ​​and calculate the voltage value of the electric wire. In this respect, if the frequency difference is increased, the time required for measurement can be shortened, but accurate detection of the peak and bottom values ​​becomes impossible, and the measurement accuracy decreases. For commercial frequencies of 50 Hz and 60 Hz, a frequency difference of about 1 Hz is realistic, but in this case, it is not possible to detect a "momentary sag" that causes a voltage drop for a period of several cycles.

[0102] On the other hand, the capacitance of the insulation of the electric wire does not change suddenly or frequently, and remains almost constant once the voltmeter is installed. Therefore, once the measured voltage calculation unit 102 measures the voltage value of the electric wire using the reference potential generated by the reference potential generation unit 101 and the corresponding differential voltage value, the detected potential is corrected using a correction value obtained based on this, and the resulting value is used as the voltage value of the electric wire, thereby avoiding the above-mentioned disadvantages.

[0103] However, the capacitance of the coating of the electric wire is not constant, but changes (gradually) depending on the temperature characteristics of the coating, humidity characteristics, aging, etc. For this reason, if a predetermined trigger condition is set and the voltage value is measured by the measured voltage calculation unit 102 when the trigger condition is satisfied, and the correction value calculation unit 111 calculates a new correction value based on this and updates the correction value, it becomes possible to prevent a decrease in measurement accuracy due to a change in capacitance.

[0104] In the above, the "predetermined trigger condition" may be immediately after installing the voltmeter 2 and turning the power on, an operational input by a user, receipt of a signal from an external device, arrival of a fixed time (e.g., 12:00), passage of a predetermined time (e.g., one hour), deviation of the measured voltage value from the upper or lower threshold limit, etc. Also, any combination of these may be used as the trigger condition.

[0105] In addition, in the case where the reference signal selection unit 18 and the wire voltage determination unit 113 assume that "the trigger condition is satisfied" for a certain period of time, the timing at which the trigger condition becomes OFF can be, for example, when a new correction value is calculated by the correction value calculation unit 111 and the correction value stored in the memory unit 14 is updated.

[0106] <Embodiment 3> The present invention can also be applied as a power sensor by combining it with a current sensor. A power sensor 3 according to a third embodiment of the present invention will be described below with reference to Figures 17A and 17B and Figure 18. The power sensor 3 according to this embodiment is connected to an AC power source in a single-phase two-wire system. The power sensor is configured to be capable of measuring the power consumption of a load connected to the power supply, and includes many components similar to those of the voltmeters described in the first and second embodiments. For this reason, the same components and processes as those already described are denoted by the same reference numerals, and repeated explanations will be omitted.

[0107] Fig. 17A is a schematic diagram showing an outline of the power sensor 3 according to this embodiment. Fig. 17B is a block diagram showing the functional configuration of the power sensor 3. As shown in Figs. 17A and 17B, the power sensor 3 according to this embodiment differs from the voltmeter 1 and voltmeter 2 in the configuration of the sensor unit 420. Also, the control unit 120 of the main body unit 51 differs from the voltmeter 1 in that it has a functional module of a power consumption calculation unit 124.

[0108] The sensor section 420 includes a first sensor head 40 having a first potential detection section 401 and a current detection section 402, and a second sensor head 41 having a second potential detection section 403. The hardware configuration of the second sensor head 41 is similar to that of the sensor head 20 of the first embodiment, but the first sensor head 40 additionally includes a current sensor element (not shown) for detecting current on the FPC 23.

[0109] The current detection unit 402 includes the current sensor element and an amplifier circuit (not shown), detects a signal related to the current value from the electric wire through the insulation, amplifies the signal, and outputs it to the main body unit 51. Note that the method of acquiring the signal related to the current value from the electric wire through the insulation is a well-known technique, so a description thereof will be omitted. Also, the first potential detection unit 401 and the second potential detection unit 403 are similar to the first potential detection unit 201 and the second potential detection unit 202 in the first embodiment, so a description thereof will be omitted.

[0110] The cable connecting the first sensor head 40 and the main body 51 also contains a signal line for electric current. Fig. 18 shows a schematic cross-sectional view of such a cable connecting the first sensor head 40 and the main body 51. As shown in Fig. 18, in addition to the voltage sensor wire containing the signal line 31, the operational amplifier positive power supply wire 32, and the operational amplifier negative power supply wire 33, the cable also contains a current sensor wire 38.

[0111] In the main body 51, the signals output from the first potential detection section 401, the current detection section 402, and the second potential detection section 403 are converted by the A / D conversion section 12 and input to the control section 120. Then, based on the input differential voltage value, the reference potential generation section 101, the measured voltage calculation section 102, and the line voltage calculation section 103 calculate the line voltage value.

[0112] The power consumption calculation unit 124 calculates the power consumed by the load to be measured based on the calculated line voltage value and the current value input from the current detection unit 402 and digitally converted by the A / D conversion unit 12.

[0113] According to the power sensor 3 described above, the power of a load connected to an AC power source in a single-phase two-wire system can be calculated using the accurate voltage value obtained by the voltage measurement technique of the present invention, so that power consumption can also be measured with high accuracy.

[0114] (Modification of power sensor) Although the power sensor 3 of the third embodiment is provided with the current detection unit 402 only in the first sensor head 40 and measures the power of a load connected to an AC power supply in a single-phase two-wire system, a current detection unit may also be provided in the other sensor head. The power sensor thus configured may be used to calculate the power consumption of a load connected to a three-phase AC power supply in a three-wire system.

[0115] Specifically, each of the sensor heads is provided with a voltage sensor and a current sensor. Therefore, by attaching sensor heads to two of the three wires corresponding to the three phases, the current values ​​of the two wires and one line voltage value can be obtained. Then, the current value of the wire to which the sensor head is not attached is calculated according to Kirchhoff's first law, and a virtual line voltage with a phase shift of 120 degrees is calculated from the line voltage of the two wires to which the sensor head is attached. Then, using these values ​​and the two actually measured current values ​​and one line voltage, the power consumption of a load connected to a three-phase AC power source can be calculated by the (pseudo) two-wattmeter method. Note that the two-wattmeter method is a well-known technique, so a description thereof will be omitted.

[0116] <Other> The above-mentioned embodiments are merely illustrative of the present invention, and the present invention is not limited to the above-mentioned specific embodiments. The present invention can be modified and combined in various ways within the scope of its technical concept. For example, the configurations according to the modifications of the above-mentioned embodiment 1 can be applied to the above-mentioned embodiment 2. In addition, the configuration of the above-mentioned embodiment 2 can be adopted in the power sensor of the above-mentioned embodiment 3 to obtain a voltage measurement value.

[0117] The voltmeter of each of the above embodiments may be provided with an alarm output means for outputting a visual or audio alarm when the measured voltage value deviates from a predetermined threshold value. The alarm may be output from an external device connected for communication, or may be output from an output means provided in the main body.

[0118] Furthermore, although the least squares method has been exemplified above as a method of linear approximation, it is of course possible to calculate the voltage value of the electric wire using other linear approximation methods, such as principal component analysis and RMA regression.

[0119] Furthermore, in each of the above embodiments, the configuration includes two measurement probes, but the present invention can naturally be applied to a power meter with one measurement probe. [Explanation of symbols]

[0120] 1, 2, 9...Voltmeter 3. Power sensor 10, 11, 51... Main body 20, 20a, 20b...Sensor head 40 1st sensor head 41 Second sensor head 21 Base section 21a, 21b: Base member 22... Potential detection electrode 23...FPC 24. Operational amplifier circuit 25 Electric field shield 26....Insulation seal 27 Magnetic field shield 28 Cover member 29 Hinge part 31 Signal line 32 Op amp positive power supply 33 Op-amp negative power supply 34 Reference potential shield 35... Voltage sensor wire sheath 36...0V shield 37 Cable jacket 38 Current sensor wire 241 Reference potential amplifier 242, 244: Potential detection amplifier 243 Differential Amplifier G... Gap

Claims

1. A voltmeter for measuring the voltage of an insulated electric wire connected to an AC power source, comprising: a voltage detection electrode for detecting a potential of the electric wire from outside the insulating coating; a reference potential output source that outputs at least a first reference potential and a second reference potential; a voltage value output section that outputs a first voltage value, which is a potential difference between the detection potential outputted from at least the voltage detection electrode and the first reference potential, and a second voltage value, which is a potential difference between the detection potential and the second reference potential; a measurement voltage calculation unit that calculates a measurement value of the voltage of the electric wire using at least the first reference potential, the second reference potential, the first voltage value, and the second voltage value; Equipped Voltmeter.

2. The measurement voltage calculation unit calculates the measurement value by a least squares method.

2. A voltmeter as claimed in claim 1.

3. The measurement voltage calculation unit calculates the measurement value by the following formula 1:

2. A voltmeter as claimed in claim 1. [0010] In addition, V １ denotes the first reference potential, V ２ denotes the second reference potential, V Ｏ１ denotes the first voltage value, V Ｏ２ indicates the second voltage value, V Ｘ indicates the measured value.

4. the first reference potential and the second reference potential are out of phase with each other by 180 degrees and have the same absolute value; 2. A voltmeter as claimed in claim 1.

5. the first reference potential and the second reference potential are lower than an output voltage of the AC power supply; 2. A voltmeter as claimed in claim 1.

6. the reference potential output source outputs the first reference potential and the second reference potential at a frequency different from a frequency of the AC power supply; 2. A voltmeter as claimed in claim 1.

7. a correction value calculation unit that calculates a correction value for the detected potential based on the measurement value and the detected potential calculated by the measurement voltage calculation unit; a wire voltage determination unit that determines, as a value of the voltage of the wire, either the measurement value calculated by the measurement voltage calculation unit or a value obtained by correcting the detected potential using the correction value; Further comprising:

2. A voltmeter as claimed in claim 1.

8. the measurement voltage calculation unit calculates the measurement value when a preset trigger condition is satisfied; the correction value calculation unit calculates the correction value when the trigger condition is satisfied; the electric wire voltage determination unit determines, when the measured value is calculated, the measured value as the value of the voltage of the electric wire, and, when the trigger condition is not satisfied, determines a value obtained by correcting the detected potential using the most recently calculated correction value as the value of the voltage of the electric wire.

8. A voltmeter as claimed in claim 7.

9. A voltage measurement method for non-contact measurement of a voltage of an insulated electric wire connected to an AC power source, comprising: acquiring a first voltage value which is a potential difference between a detected potential detected from the electric wire and a first reference potential; acquiring a second voltage value which is a potential difference between a detection potential detected from the electric wire and a second reference potential; calculating a voltage measurement of the electric wire using at least the first reference potential, the second reference potential, the first voltage value, and the second voltage value; Equipped Voltage measurement method.

10. 1. A computing device for measuring a voltage of an electric wire, the computing device being used together with a voltage detection electrode that is connected to an AC power source and detects a potential of the electric wire from an outside of the insulating coating of the electric wire, the computing device comprising: outputting at least a first reference potential and a second reference potential, the values ​​of which are set in advance; acquiring a first voltage value that is a potential difference between a detected potential detected from the electric wire and the first reference potential; acquiring a second voltage value that is a potential difference between a detected potential detected from the electric wire and the second reference potential; and calculating a measurement value of the voltage of the electric wire using at least the first reference potential, the second reference potential, the first voltage value, and the second voltage value. Computing device.

11. A power meter for measuring power consumption of a load connected to an AC power source, comprising: a current sensor connected to the AC power source and configured to detect a current in the insulated electric wire from outside the insulating coating of the electric wire; a voltage detection electrode for detecting a potential of the electric wire from outside the insulating coating; a reference potential output source that outputs at least a first reference potential and a second reference potential; a voltage value output section that outputs a first voltage value, which is a potential difference between the detection potential outputted from at least the voltage detection electrode and the first reference potential, and a second voltage value, which is a potential difference between the detection potential and the second reference potential; a measurement voltage calculation unit that calculates a measurement value of the voltage of the electric wire using at least the first reference potential, the second reference potential, the first voltage value, and the second voltage value; a power consumption calculation unit that calculates the power consumption of the load based on the value of the current detected by the current sensor and the value of the voltage calculated by the measured voltage calculation unit; Equipped Power meter.

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