WO2022173051A1 - 電圧測定装置 - Google Patents

電圧測定装置 Download PDF

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Publication number
WO2022173051A1
WO2022173051A1 PCT/JP2022/005830 JP2022005830W WO2022173051A1 WO 2022173051 A1 WO2022173051 A1 WO 2022173051A1 JP 2022005830 W JP2022005830 W JP 2022005830W WO 2022173051 A1 WO2022173051 A1 WO 2022173051A1
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Prior art keywords
voltage
electrode
cable
measurement
unit
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PCT/JP2022/005830
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English (en)
French (fr)
Japanese (ja)
Inventor
正寛 川口
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日本電産リード株式会社
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Priority to JP2022580715A priority Critical patent/JPWO2022173051A1/ja
Publication of WO2022173051A1 publication Critical patent/WO2022173051A1/ja

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/04—Voltage dividers
    • G01R15/06—Voltage dividers having reactive components, e.g. capacitive transformer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof

Definitions

  • the present invention relates to a voltage measuring device that clamps and measures a cable to be measured.
  • the voltage of the coated cable is measured using this voltage detector, the thickness of the cable coating is d and the dielectric constant of the cable coating is ⁇ .
  • the voltage detection device described above when the cable to be measured changes, the thickness d of the cable coating and the dielectric constant ⁇ of the cable coating change, and the capacitance C between the object to be detected and the detection electrode changes. . As a result, the voltage detection is affected by the characteristics of the cable to be measured, and the voltage measurement accuracy is lowered.
  • An object of the present invention is to provide a voltage measurement device that facilitates improving voltage measurement accuracy.
  • a voltage measuring device includes a clamp section that clamps a cable to be measured, a first electrode and a second electrode that are arranged to face the cable clamped by the clamp section, and a stabilizing section connecting the first electrode to ground through a capacitor; an amplifying section with variable amplification factor for amplifying the voltage obtained from the first electrode; and measuring the voltage of the cable.
  • a mode input unit that selectively accepts as mode settings a measurement mode for calibration and a calibration mode for calibrating the output voltage of the amplification unit; and a reference voltage output that outputs a preset reference voltage that periodically changes.
  • a measuring unit for measuring the output voltage of the amplifying unit, connecting the second electrode to the ground when in the measurement mode, and connecting the second electrode to the reference voltage output unit when in the calibration mode. and a switching unit that, in the calibration mode, the output voltage of the amplifying unit is set to the measurement magnification times the voltage of the cable based on the measurement value of the measurement unit, the reference voltage, and a preset measurement magnification. and a calibration processing unit that adjusts the amplification factor so that
  • a voltage measurement device with such a configuration can easily improve the voltage measurement accuracy.
  • FIG. 2 is a front view showing the inside by seeing through the clamp arm and the front wall of the housing shown in FIG. 1 ; 3 is a front view of electrodes E1 and E2 shown in FIG. 2 as seen from the Z direction;
  • FIG. 2 is a circuit diagram showing an example of an electrical configuration in a calibration mode of the clamp-type voltage measuring device 1 shown in FIG. 1;
  • FIG. 2 is a circuit diagram showing an example of an electrical configuration in a measurement mode of the clamp-type voltage measuring device 1 shown in FIG. 1;
  • FIG. 4 is a flow chart showing an example of operation of the clamp-type voltage measuring device 1 in a calibration mode; 4 is a flow chart showing an example of the operation of the clamp-type voltage measuring device 1 in a measurement mode;
  • a clamp-type voltage measuring device 1 shown in FIG. The housing 3 is connected via a coaxial cable 4 to a measuring device such as an oscilloscope or data logger.
  • the clamp section 2 has a pair of clamp arms 21 and 22 .
  • a proximal end of the clamp arm 21 is supported by a shaft 27 attached to the housing 3 .
  • the clamp arm 21 is swingable around the shaft 27 .
  • Holding grooves 211 and 221 into which the cable CBL is fitted are formed in the facing surfaces of the clamp arms 21 and 22 .
  • the clamp arm 21 is biased toward the clamp arm 22 by a torsion spring (not shown).
  • the cable CBL is clamped between the clamp arm 21 and the clamp arm 22 by the biasing force of the torsion spring.
  • the clamp arm 22 is fixedly connected to the housing 3. It should be noted that the clamp arm 22 may be swingable like the clamp arm 21 .
  • the clamp arms 21 and 22 and the housing 3 are made of an insulating material such as a resin material.
  • a housing space 28 is provided inside the clamp arm 22 .
  • the accommodation space 28 communicates with the internal space of the housing 3 .
  • a substantially plate-shaped electrode E1 (first electrode) and an electrode E2 (second electrode) are disposed in the accommodation space 28 .
  • the electrodes E1 and E2 are arranged so as to face the cable CBL with a gap in the extending direction of the cable CBL.
  • the electrodes E1 and E2 may be formed as conductor patterns on a printed wiring board, for example, or may be metal plates.
  • the electrodes E1 and E2 are arranged facing or in contact with the inner wall surface of the holding groove 221 of the clamp arm 22 .
  • the electrodes E1 and E2 are arranged to face the cable CBL clamped by the clamp section 2 via the wall of the holding groove 221 made of an insulating material.
  • a circuit board 31 is accommodated in the housing 3 .
  • a terminal T3 and an electrode E1 of the circuit board 31 are connected via a wire W1, and a terminal T4 and an electrode E2 are connected via a wire W2.
  • a layer 32 is formed.
  • the conductive layer 32 may be, for example, a metal foil such as an aluminum foil, may be coated with a conductive paint, may be a plated layer, or may be a metal plate. In the example shown in FIG. 2, the conductive layer 32 is not formed on the wall of the holding groove 221 located between the cable CBL clamped by the clamping section 2 and the electrode E1 and on the periphery of the electrode E1.
  • the outer wall surface of the clamp-type voltage measuring device 1 is made insulative, and the cable CBL clamped by at least the clamp section 2 on the inner wall surface of the housing 3 and the inner wall surface of the clamp arm 22 and the electrodes E1 and E2 are connected.
  • the parts except for the parts located in between are made conductive.
  • the outer wall surface of the clamp-type voltage measuring device 1 is insulated, for example, even if the conductor portion of the cable CBL is exposed, current will not flow from the cable CBL to the electrodes E1 and E2 and the circuit board 31. Therefore, the risk of damage to the clamp-type voltage measuring device 1 is reduced. Moreover, the safety of the user who operates the clamp-type voltage measuring device 1 is improved. Also, by providing the conductive layer 32, electromagnetic noise from the external environment can be reduced.
  • the electrodes E1 and E2 are not necessarily arranged inside the clamp part 2 and are not necessarily arranged to face the cable CBL via an insulating material.
  • the electrodes E1 and E2 may be exposed to the holding groove 221, for example, and may be arranged to face each other while being in contact with the cable CBL.
  • the clamp-type voltage measuring device 1 measures the cable voltage, which is the voltage of the core wire W, via the electrostatic capacitances Cx 1 and Cx 2 generated by arranging the core wire W of the cable CBL and the electrodes E1 and E2 to face each other. Detect Vx.
  • the capacitances Cx 1 and Cx 2 are inversely proportional to the facing distance d between the core wire W of the cable CBL and the electrodes E1 and E2. Therefore, the shorter the facing distance d, the greater the capacitances Cx 1 and Cx 2 , and the easier the detection of the cable voltage Vx. Also, when the facing distance d changes, the voltage obtained via the capacitances Cx1 and Cx2 fluctuates.
  • clamp arms 21 and 22 have insufficient force to clamp cable CBL with only the urging force of a torsion spring (not shown), and a gap is generated between cable CBL and holding groove 221 to increase opposing distance d.
  • the capacitances Cx 1 and Cx 2 may decrease.
  • the cable CBL may sway, causing the facing distance d to fluctuate, and the electrostatic capacitances Cx 1 and Cx 2 to fluctuate.
  • the clamp arms 21 and 22 can be fastened with screws 25 to firmly clamp the cable CBL. It is possible to reduce the risk of fluctuations in the capacitances Cx 1 and Cx 2 due to reduction and shaking of the cable CBL.
  • a switch SW, a reference voltage output section PS, a stabilizing section 5, an amplifying section A, a measuring section 7, terminals T1 and T2, and a control section 8 are formed on a circuit board 31 and accommodated in a housing 3.
  • FIG. At least one of the measurement unit 7 , the mode switch 9 , and the control unit 8 is not necessarily housed in the housing 3 , and may be configured outside the housing 3 .
  • a conductor core W is covered with an insulating coating J.
  • the electrostatic capacitance formed by the core wire W and the electrode E1 facing each other is represented by the electrostatic capacitance Cx1
  • the electrostatic capacitance formed by the core wire W and the electrode E2 facing each other is represented by capacitance Cx2 .
  • the stabilization unit 5 includes a parallel circuit 51, a resistor R2, and a capacitor C2.
  • a parallel circuit 51 is a parallel circuit of a capacitor C1 and a resistor R1.
  • the electrode E1 is connected to one end P1 of the parallel circuit 51 and the non-inverting input terminal of the amplifier A1 via the terminal T3 and the wiring W1 shown in FIG.
  • the other end P2 of the parallel circuit 51 is connected to the circuit ground GND via the capacitor C2.
  • the other end P2 of the parallel circuit 51 is connected to the circuit ground GND via the resistor R2.
  • a circuit ground GND is connected to the conductive layer 32 .
  • the stabilizing section 5 has a function of stabilizing the potential of the input voltage Vin input from the electrode E1 to the non-inverting input terminal of the amplifier A1, and a function as a filter, which will be described later. If the clamp-type voltage measuring device 1 did not include the stabilizing section 5, the electrode E1 would simply be connected to the non-inverting input terminal of the high-impedance amplifier A1, so the electrode E1 would have no reference potential. It is in an electrically floating state, and the wiring from the electrode E1 to the non-inverting input terminal acts like an antenna. Therefore, the input voltage Vin input to the non-inverting input terminal of the amplifier A1 becomes unstable.
  • the stabilizing section 5 by providing the stabilizing section 5 and connecting the electrode E1 to the circuit ground GND via the capacitors C1 and C2, a reference potential for the input voltage Vin can be provided and the input voltage Vin can be stabilized.
  • the stabilizing section 5 does not necessarily need to have a function as a filter, which will be described later, as long as it can stabilize the input voltage Vin.
  • the stabilizing section 5 may have a configuration in which only the capacitor C2 is connected to the electrode E1.
  • the electrostatic capacitances C 1 and C 2 of the capacitors C1 and C2 are sufficiently large, for example, 100 to 1000 times or more as large as the assumed electrostatic capacitances Cx 1 and Cx 2 .
  • the impedances of the capacitors C1 and C2 are made smaller than the impedances of the capacitances Cx1 and Cx2 to the extent that they can be ignored.
  • the amplifier section A includes an amplifier A1, a feedback resistor Ra, and a variable resistor Rx.
  • Amplifier A1 is a so-called operational amplifier.
  • a non-inverting input terminal of the amplifier A1 is connected to one end P1 of the parallel circuit 51 .
  • One end of the feedback resistor Ra is connected to the inverting input terminal of the amplifier A1, and the other end of the feedback resistor Ra is connected to the output terminal of the amplifier A1.
  • the inverting input terminal of amplifier A1 is connected to circuit ground GND through a variable resistor Rx.
  • the amplifier section A is a non-inverting amplifier.
  • a digital potentiometer for example, can be used as the variable resistor Rx.
  • the variable resistor Rx is not limited to a digital potentiometer.
  • Various parts or circuits whose resistance values can be changed can be used as the variable resistor Rx.
  • the feedback resistor Ra may be a variable resistor, and the amplification factor G of the amplifier section A may be adjustable by changing the resistance value Ra of the feedback resistor Ra.
  • the feedback resistor Ra affects the frequency characteristics of the amplifier A, it is more preferable to adjust the amplification factor G of the amplifier A by changing the variable resistor Rx which does not affect the frequency characteristics.
  • the amplifying unit A may be an inverting amplifier.
  • the electrode E1 will be connected to the same inverting input terminal to which the feedback resistor is connected. In this case, a leakage current flows through a current path from the electrode E1 to the output terminal of the amplifier via the feedback resistor, which may affect the input voltage Vin.
  • the amplifier A is a non-inverting amplifier
  • the electrode E1 is connected to the high-impedance non-inverting input terminal of the amplifier A1, and no leakage current occurs via the feedback resistor Ra.
  • the possibility that the leakage current affects the input voltage Vin is reduced. Therefore, it is more preferable to use the amplifier section A as a non-inverting amplifier.
  • the output terminal of the amplifier A1 is connected to the measuring section 7 and the terminal T1.
  • Terminal T2 is connected to circuit ground GND.
  • the terminal T1 is connected to the core wire of the coaxial cable 4, and the terminal T2 is connected to the shield wire of the coaxial cable 4.
  • the output voltage Vout of the amplifier A1 is output via the coaxial cable 4 to a measuring device such as an oscilloscope or data logger. That is, the output voltage Vout of the amplifier A1 represents the measurement result of the clamp-type voltage measuring device 1.
  • the clamp-type voltage measuring device 1 outputs the voltage of the cable voltage Vx at the measurement magnification M as the output voltage Vout. Since the measurement magnification M is known, the measuring device connected to the clamp-type voltage measuring device 1 can correctly recognize the measured cable voltage Vx from the output voltage Vout. However, unless the output voltage Vout is a measurement magnification M times the cable voltage Vx, the output voltage Vout does not correctly represent the measured cable voltage Vx. Therefore, the amplification factor G is adjusted so that the output voltage Vout becomes the measurement magnification M times the cable voltage Vx by the calibration mode described later.
  • the measurement magnification M is, for example, 1/100.
  • the cable CBL is not particularly limited, but is assumed to be, for example, a motor drive power cable for an electric vehicle.
  • a cable voltage Vx which is an AC voltage having a rectangular periodic waveform by PWM (Pulse Width Modulation) output from an inverter, is to be measured.
  • a cable voltage Vx of the core wire W is applied to one end P1 of the parallel circuit 51 via a capacitance Cx1.
  • Cx1 a capacitance
  • a series circuit of the resistor R1 and the capacitor C2 is configured.
  • a series circuit of the resistor R1 and the capacitor C2 is a so-called integration circuit and functions as a low-pass filter that passes low frequency components.
  • the series circuit of the resistor R1 and the capacitor C2 corresponds to the period of the square wave.
  • a low frequency component to be applied can be input to the amplifier A1.
  • a series circuit of the capacitor C1 and the resistor R2 is configured.
  • a series circuit of the capacitor C1 and the resistor R2 is a so-called differentiating circuit and functions as a high-pass filter that passes high frequency components.
  • the voltage across the resistor R2 and the voltage across the capacitor C1 are added to the input terminal of the amplifier A1.
  • a high frequency component corresponding to the falling can be input to the amplifier A1.
  • both the low frequency component corresponding to the period of the rectangular wave and the high frequency component corresponding to the rise and fall of the rectangular wave are superimposed and input to the input terminal of the amplifier A1. Therefore, the AC voltage waveform detected from the core wire W can be accurately amplified by the amplifier A1 and output to the measuring device.
  • the reference voltage output unit PS outputs a preset reference voltage Vs that changes periodically.
  • the reference voltage Vs may change periodically, and may be, for example, a sine wave alternating current or a square wave pulse, but has a signal waveform similar to the voltage to be detected on the cable CBL is preferred.
  • the reference voltage output section PS preferably outputs a rectangular wave voltage as the reference voltage Vs.
  • the switch SW is a switching unit that connects the electrode E2 to the circuit ground GND in the measurement mode and connects the electrode E2 to the reference voltage output unit PS in the calibration mode.
  • the changeover switch SW switches connection between the measurement mode and the calibration mode according to a control signal from the control unit 8, for example.
  • the mode switch 9 is, for example, a mode setting switch that can be operated by the user. By operating the mode switch 9, it is possible to selectively set the measurement mode and the calibration mode. A signal indicating the mode set by the mode switch 9 is output to the control section 8 .
  • the measuring unit 7 measures the output voltage Vout of the amplifying unit A.
  • the measurement unit 7 is configured using, for example, an analog-to-digital converter.
  • the measurement unit 7 outputs the measured value Vm of the output voltage Vout to the control unit 8 . Since the cable voltage Vx to be measured is AC, the output voltage Vout also has an AC waveform. Therefore, the measurement unit 7 preferably measures the peak-to-peak value of the output voltage Vout as the measured value Vm.
  • the control unit 8 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a RAM (Random Access Memory) that temporarily stores data, a nonvolatile storage device such as a flash memory, and peripheral circuits thereof. is configured using The control unit 8 functions as a mode input unit 81 and a calibration processing unit 82 by executing the programs stored in the storage elements described above.
  • a CPU Central Processing Unit
  • RAM Random Access Memory
  • the mode input section 81 has a measurement mode for measuring the cable voltage Vx, which is the voltage of the core wire W of the cable CBL, and a calibration mode for calibrating the output voltage Vout of the amplifier section A based on the signal output from the mode switch 9. Mode settings are selectively accepted as mode settings.
  • the mode input unit 81 connects the electrode E2 to the circuit ground GND by the changeover switch SW when the received mode setting is the measurement mode, and connects the electrode E2 to the reference voltage output unit PS by the changeover switch SW when it is in the calibration mode. .
  • the mode input unit 81 is not necessarily limited to switching the changeover switch SW.
  • the mode switch 9 and the changeover switch SW may be composed of double-pole double-throw switches.
  • One pole of the double-pole, double-throw switch may be used as the mode switch 9 and the other pole as the switch SW. In this way, even if the mode input unit 81 does not switch the switch SW, the switch SW can be switched according to the mode.
  • the mode input unit 81 only needs to be able to receive a signal indicating mode setting from the outside, and the clamp-type voltage measuring device 1 does not have to include the mode switch 9 .
  • the calibration processing unit 82 determines that the output voltage Vout of the amplification unit A is equal to the measurement magnification of the cable voltage Vx based on the measurement value Vm of the measurement unit 7, the reference voltage Vs, and a preset measurement magnification M.
  • the amplification factor G of the amplification section A is adjusted to the amplification factor Gx so that it becomes M times.
  • the calibration processing unit 82 calculates the current amplification factor G, that is, the amplification factor G when the output voltage Vout is measured by the measurement unit 7 in the calibration mode. , an amplification factor Gx, which is a target value after calibration at which the measurement magnification M is obtained, is calculated.
  • Gx ⁇ G ⁇ Vs ⁇ Cx 2 /(Cx 1 +Cx 2 ) ⁇ M/Vm (1)
  • the calibration processing unit 82 can calculate the amplification factor Gx based on Equation (2).
  • the amplification factor Gx based on the equation (1), it is necessary to measure the capacitances Cx 1 and Cx 2 , whereas according to the equation (2), the capacitances Cx 1 and Cx 2 are Since there is no need for measurement, the calculation of the amplification factor Gx is facilitated.
  • the capacitance Cx1 and the capacitance Cx2 are equal , and the area S1 and the area S2 are not necessarily equal. However, if the area S1 and the area S2 are equal , the capacitance Cx 1 and the capacitance Cx 2 can be equal. Therefore, it is more preferable to make the area S1 and the area S2 equal in that the calculation of the amplification factor Gx can be facilitated using the equation ( 2 ).
  • the calibration processing unit 82 adjusts the amplification factor of the amplification part A to the amplification factor Gx by adjusting the resistance value of the variable resistor Rx.
  • the cable voltage Vx is a voltage obtained by dividing the reference voltage Vs by the series circuit of the capacitance Cx2 and the stabilizer 5 and the capacitance Cx1.
  • the impedances of the capacitors C1 and C2 of the stabilizing section 5 are so small that they can be ignored with respect to the impedances of the capacitances Cx1 and Cx2 . Therefore, the cable voltage Vx is a value obtained by dividing the reference voltage Vs by the capacitances Cx1 and Cx2 , and can be approximated by the following equation ( 3 ).
  • the resistance value Rx should be adjusted so as to satisfy the following formula (6).
  • the calibration processing unit 82 calculates the resistance value Rx by substituting the amplification factor Gx obtained by the equation (1) or the equation (2) into the equation (7), and calculates the resistance value of the variable resistor Rx by the equation
  • the amplification unit A can be adjusted to the amplification factor Gx.
  • the clamp-type voltage measuring device 1 can be calibrated so that the output voltage Vout of the amplifying section A satisfies the following equation (8).
  • the user when calibrating the clamp-type voltage measuring device 1, the user puts the core wire W into a state where no voltage is applied, for example, by removing the cable CBL from the device. In this state, the user clamps the cable CBL with the clamp unit 2 and operates the mode switch 9 to set the calibration mode. Then, a signal indicating the calibration mode is output from the mode switch 9 to the controller 8 .
  • the mode input unit 81 accepts the setting of the calibration mode and switches the selector switch SW to the reference voltage output unit PS side (step S1).
  • the reference voltage Vs output from the reference voltage output unit PS is supplied to the electrode E2, and from the electrode E2 through the capacitance Cx2 , the core wire W, and the capacitance Cx1 .
  • An input voltage Vin is induced across E1.
  • the input voltage Vin is amplified with an amplification factor G by the amplification section A and output to the measurement section 7 as the output voltage Vout. Since the output voltage Vout has an AC waveform as described above, the peak-to-peak voltage of the output voltage Vout is measured by the measurement section 7 and the measured value Vm is output to the control section 8 .
  • the calibration processing unit 82 calculates the resistance value Rx from Equation (7) based on the calculated amplification factor Gx (step S3).
  • the calibration processing unit 82 sets the resistance value of the variable resistor Rx to the calculated Rx (step S4).
  • the amplification factor of the amplification section A is set to Gx.
  • the clamp-type voltage measuring device 1 can be calibrated so that the output voltage Vout becomes the measurement magnification M of the cable voltage Vx, that is, so that the equation (8) is satisfied.
  • the measurement mode When measuring the cable voltage Vx while the cable CBL is in use, the user clamps the cable CBL connected to the device with the clamp unit 2 and operates the mode switch 9 to set the measurement mode. Then, a signal indicating the measurement mode is output from the mode switch 9 to the controller 8 .
  • mode input unit 81 accepts the setting of the measurement mode, and switches switch SW to the circuit ground GND side as shown in FIG. (step S11). Then, the cable voltage Vx to be measured supplied to the core wire W induces an input voltage Vin to the electrode E1 via the capacitance Cx1 .
  • the amplification unit A amplifies the input voltage Vin to the output voltage Vout with the calibrated amplification factor Gx.
  • the output voltage Vout is output to the terminal T1 as a signal indicating the result of measurement by the clamp-type voltage measuring device 1.
  • the electrostatic capacitance Cx 1 is represented by ⁇ S 1 /d, and the facing distance d depending on the thickness of the coating J, the dielectric constant ⁇ of the coating J, etc. change depending on the cable CBL to be measured. Then the capacitance Cx 1 also changes. Therefore, when the cable CBL changes, the input voltage Vin induced by the cable voltage Vx also changes, so that the correct output voltage Vout cannot be obtained.
  • the clamp-type voltage measuring device 1 the cable CBL to be measured is clamped by the clamp unit 2, and the correct output voltage Vout adapted to the cable CBL to be measured can be easily obtained by performing calibration in the calibration mode. Obtainable. Therefore, the clamp-type voltage measurement device 1 can easily improve the voltage measurement accuracy.
  • a voltage measuring device includes a clamp section that clamps a cable to be measured, and a first electrode and a second electrode that are arranged to face the cable clamped by the clamp section. , a stabilizing section that connects the first electrode to ground via a capacitor; an amplifying section that can change the amplification factor and amplifies the voltage obtained from the first electrode; A mode input unit that selectively accepts as mode settings a measurement mode for measuring and a calibration mode for calibrating the output voltage of the amplification unit, and a reference that outputs a preset reference voltage that changes periodically.
  • a voltage output unit a measurement unit for measuring the output voltage of the amplification unit, the second electrode being connected to the ground in the measurement mode, and the second electrode being connected to the reference voltage output unit in the calibration mode. and a switching unit connected to the calibrating mode, based on the measured value of the measuring unit, the reference voltage, and a preset measurement magnification, the output voltage of the amplifying unit changes from the measured voltage of the cable. and a calibration processing unit that adjusts the amplification factor so as to obtain a magnification factor.
  • the first electrode and the second electrode are arranged to face the cable, a capacitance is generated between them and the cable.
  • a preset reference voltage is applied to the second electrode and the capacitance between the first and second electrodes and the cable produces a voltage on the first electrode.
  • the voltage generated at the first electrode is amplified by the amplification section, and the amplified output voltage is measured by the measurement section.
  • the amplification factor of the amplification section is adjusted by the calibration processing section based on the measurement value of the measurement section, the reference voltage, and the measurement magnification so that the output voltage of the amplification section becomes the measurement magnification times the voltage of the cable. be.
  • the amplification of the amplifier is adjusted according to the cable to be measured, so it becomes easy to improve the voltage measurement accuracy.
  • the amplifier is preferably a non-inverting amplifier.
  • a non-inverting amplifier having a high input impedance is used as the amplifying section, so the possibility that the input impedance of the amplifying section affects the voltage of the first electrode is reduced.
  • the amplifying unit includes an amplifier having a non-inverting input terminal to which the voltage obtained from the first electrode is input, a feedback resistor connecting an inverting input terminal and an output terminal of the amplifier, and an inverting input of the amplifier.
  • a variable resistor connecting the terminal and the ground is preferably provided, and the amplification factor can be changed by changing the resistance value of the variable resistor.
  • the amplification factor can be adjusted by changing the resistance value of the variable resistor while fixing the resistance value of the feedback resistor.
  • a non-inverting amplifier can also change the gain by changing the resistance value of the feedback resistor.
  • the feedback resistor also affects frequency characteristics. Therefore, according to this configuration, the amplification factor can be adjusted while the resistance value of the feedback resistor is fixed. Therefore, it is possible to change the amplification factor while reducing the influence on the frequency characteristics.
  • the capacitance between the cable and the first electrode and the capacitance between the cable and the second electrode are substantially equal.
  • the area of the first electrode and the area of the second electrode are substantially equal.
  • the capacitance between the cable and the first electrode is Cx 1
  • the capacitance between the cable and the second electrode is Cx 2
  • the reference voltage is Vs
  • the measurement value of the measurement unit is Vm
  • the measurement magnification is M
  • the amplification factor when the output voltage is measured by the measurement section in the calibration mode is G
  • the calibration processing section calculates the amplification factor by the following formula ( It is preferable to adjust to Gx obtained in 1).
  • Gx ⁇ G ⁇ Vs ⁇ Cx 2 /(Cx 1 +Cx 2 ) ⁇ M/Vm (1)
  • the capacitance Cx1 and the capacitance Cx2 are substantially equal, and that the equation (1) is approximated by the following equation ( 2 ).
  • equation (1) is approximated by the equation (2), so the capacitances Cx 1 and Cx 2 are unknown. Also, equation (2) is used to calculate an appropriate amplification factor Gx to be adjusted by calibration.

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  • General Physics & Mathematics (AREA)
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  • Measurement Of Current Or Voltage (AREA)
PCT/JP2022/005830 2021-02-15 2022-02-15 電圧測定装置 WO2022173051A1 (ja)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5473244A (en) * 1992-09-17 1995-12-05 Libove; Joel M. Apparatus for measuring voltages and currents using non-contacting sensors
JP2002340939A (ja) * 2001-05-16 2002-11-27 Hitachi Ltd 被覆電力線用電圧測定装置
JP2017040526A (ja) * 2015-08-19 2017-02-23 日置電機株式会社 電圧検出センサおよび測定装置
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US20190081601A1 (en) * 2017-09-08 2019-03-14 Analog Devices Global Unlimited Company Method of and Apparatus for Reducing the Influence of a Common Mode Signal on a Differential Signal and to Systems including such an Apparatus

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