JP7009025B2 - Voltage measuring device, voltage measuring method - Google Patents

Description

The present invention relates to a voltage measuring device and a voltage measuring method capable of measuring the voltage of an object to be measured in a non-contact manner.

Patent Document 1 discloses a voltage measuring device 400 capable of measuring the voltage V1 of the measurement object 404 as shown in FIG. 9 in a non-contact manner. In the voltage measuring device 400, the detection electrode 412 of the probe unit 402 is arranged in a non-contact state in the vicinity of the measurement object 404, and a capacitance C0 is formed between the detection electrode 412 and the measurement object 404. ing.

In the voltage measuring device 400, when the variable capacitance element 413 is driven by the AC signal S1 from the main body 403, an alternating current i flows due to a change in the capacitance of the variable capacitance element 413. The magnitude of the current i is determined by the voltage difference between the voltage V1 of the object to be measured 404 and the voltage V4 of the shield case of the probe unit 402. The current i is measured as an AC voltage V2 with the detection resistance 415, and a shield voltage V4 corresponding to the amplitude is generated from the voltage generation circuit 425.

With this configuration, the shield voltage V4 of the voltage measuring device 400 is controlled so that the current i becomes 0, and at this time, the shield voltage V4 becomes the same voltage as the voltage V1 of the measurement object 404. Therefore, the voltage V1 of the object to be measured 404 can be measured by measuring the shield voltage V4 with the voltmeter 426.

JP-A-2007-132926

In the voltage measuring device 400, for example, when measuring a high voltage of several kV, the shield case of the probe unit 402 becomes a high voltage. Therefore, in order to ensure the safety of the measuring device, it is necessary to have a high insulation design around the shield case and measures to prevent electric shock due to damage. Therefore, the cost of the voltage measuring device 400 is increased.

Therefore, an object of the present invention is to provide a voltage measurement technique capable of non-contact measurement of a high voltage without incurring a high cost.

In order to solve the above problems, the voltage measuring device according to the first aspect of the present invention is a voltage measuring device that measures an AC voltage of a first frequency, and is connected to an electrode and the electrode to have a second frequency. A variable voltage source that outputs an AC voltage, a current detector that detects the current flowing between the electrode and the variable voltage source, and the magnitude of the first frequency component and the second frequency from the detected current. A difference extraction unit that extracts and outputs a value corresponding to the difference from the magnitude of the component, a voltage adjustment unit that changes the output voltage of the variable voltage source so that the output of the difference extraction unit becomes 0, and the above. It is characterized by including a calculation unit for calculating an AC voltage of the first frequency based on the output voltage of the variable voltage source and the first frequency and the second frequency.
According to the voltage measuring device according to the first aspect of the present invention, since the measuring side can measure at a voltage much lower than the voltage to be measured, expensive high withstand voltage components are not required as components of the voltage measuring device. It becomes. In addition, since high voltage is not generated inside the voltage measuring device, high insulation design and electric shock prevention measures are not required. Therefore, it is possible to prevent the cost increase as in the prior art, and it is possible to construct the voltage measuring device at low cost.

Here, the calculation unit can calculate the AC voltage of the first frequency by multiplying the ratio of the second frequency and the first frequency by the output voltage of the variable voltage source.
Further, the electrode and the variable voltage source may be connected via a capacitor.

In order to solve the above problems, the voltage measuring device according to the second aspect of the present invention is a voltage measuring device that measures the AC voltage of the first frequency, and is an electrode, a plurality of measuring units, and a comprehensive calculation unit. The measuring unit is connected to the electrode and outputs a variable voltage source having a different unique frequency, and a current detection that detects a current flowing between the electrode and the variable voltage source. The output of the difference extraction unit and the difference extraction unit that extracts and outputs a value corresponding to the difference between the magnitude of the first frequency component and the magnitude of the unique frequency component from the detected current and the unit. The AC voltage of the first frequency is based on the voltage adjusting unit that changes the output voltage of the variable voltage source so as to be 0, the output voltage of the variable voltage source, the first frequency, and the inherent frequency. The comprehensive calculation unit is characterized by calculating the AC voltage of the first frequency based on the AC voltage of the first frequency calculated for each measurement unit. do.
According to the voltage measuring device according to the second aspect of the present invention, when the AC voltage of the first frequency contains a noise component, even if the measured voltage affected by the noise at a certain frequency is obtained, the other At the frequency of, a measured voltage that is not affected by noise can be obtained. Therefore, in addition to the effect of the voltage measuring device of the first aspect, the influence of the noise component included in the AC voltage of the first frequency can be reduced.

In order to solve the above problems, the voltage measuring device according to the third aspect of the present invention is a voltage measuring device that measures an AC voltage of a first frequency, and is a first switchable by connecting an electrode and the electrode. A variable voltage source that outputs an AC voltage of two frequencies, a current detection unit that detects the current flowing between the electrode and the variable voltage source, and the magnitude of the first frequency component and the said from the detected current. A difference extraction unit that extracts and outputs a value corresponding to the difference from the magnitude of the second frequency component, and a voltage adjustment unit that changes the output voltage of the variable voltage source so that the output of the difference extraction unit becomes 0. And a calculation unit that calculates the AC voltage for each frequency of the first frequency based on the output voltage of the variable voltage source, the first frequency, and the second frequency for each switched second frequency. It is characterized by including a comprehensive calculation unit for calculating the AC voltage of the first frequency based on the AC voltage of each frequency of the first frequency.
According to the voltage measuring device according to the third aspect of the present invention, when the AC voltage of the first frequency contains a noise component, even if the measured voltage affected by the noise at a certain frequency is obtained, the other At the frequency of, a measured voltage that is not affected by noise can be obtained. Therefore, in addition to the effect of the voltage measuring device of the first aspect, the influence of the noise component contained in the AC voltage of the first frequency can be reduced.

In order to solve the above problems, the voltage measuring method according to the fourth aspect of the present invention is a voltage measuring method for measuring an AC voltage of the first frequency, and is a measurement target to which the AC voltage of the first frequency is applied. When an AC voltage of a second frequency is applied to an object via a capacitance, the magnitude of the first frequency component and the magnitude of the second frequency component are the same for the current flowing through the capacitance. It is characterized in that the AC voltage of two frequencies is adjusted, and the AC voltage of the first frequency is calculated based on the AC voltage of the second frequency, the first frequency and the second frequency at that time.
According to the voltage measuring method according to the fourth aspect of the present invention, the measuring side can measure at a voltage much lower than the voltage to be measured, so that no expensive high withstand voltage component is required as a component of the voltage measuring device. It becomes. In addition, since high voltage is not generated inside the voltage measuring device, high insulation design and electric shock prevention measures are not required. Therefore, it is possible to prevent the cost increase as in the prior art, and it is possible to construct the voltage measuring device at low cost.

In order to solve the above problems, the voltage measuring method according to the fifth aspect of the present invention is a voltage measuring method for measuring an AC voltage of the first frequency, and is a measurement target to which the AC voltage of the first frequency is applied. With respect to the current flowing through the capacitance when an AC voltage having a unique frequency is applied to the object via the capacitance, the intrinsic is such that the magnitude of the first frequency component and the magnitude of the intrinsic frequency component are the same. The process of adjusting the AC voltage of the frequency of 1 and calculating the AC voltage of the 1st frequency based on the AC voltage of the specific frequency at that time and the 1st frequency and the specific frequency is the unique process. It is characterized in that a plurality of operations are performed with different frequencies, and the AC voltage of the first frequency is calculated based on the calculated AC voltage of the first frequency for each unique frequency.
According to the voltage measuring method according to the fifth aspect of the present invention, when the AC voltage of the first frequency contains a noise component, even if the measured voltage affected by the noise at a certain frequency is obtained, the other At the frequency of, a measured voltage that is not affected by noise can be obtained. Therefore, in addition to the effect of the voltage measuring method of the fifth aspect, the influence of the noise component contained in the AC voltage of the first frequency can be reduced.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a voltage measurement technique capable of non-contact measurement of high voltage without incurring cost increase.

It is a figure explaining the measurement principle of the voltage measuring instrument of this invention. It is a figure which shows the structure of the 1st Embodiment of the voltage measuring instrument of this invention. It is a figure which shows the structure of the 2nd Embodiment of the voltage measuring instrument of this invention. It is a figure which shows the structure of the 3rd Embodiment of the voltage measuring instrument of this invention. It is a figure which shows the structure of the 4th Embodiment of the voltage measuring instrument of this invention. It is a figure which shows the structure of the 5th Embodiment of the voltage measuring instrument of this invention. It is a figure explaining the measurement principle of the 2nd Embodiment of the voltage measuring instrument of this invention. It is a figure explaining the measurement principle of the 3rd Embodiment of the voltage measuring instrument of this invention. It is a figure explaining the conventional non-contact type voltage measuring instrument.

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating a measurement principle of the voltage measuring instrument of the present invention. In the voltage measuring instrument of the present invention, an AC voltage is a measurement target, and in this figure, an AC voltage Vx having a frequency fx is a measurement target. A variable voltage source 110 having a variable output voltage Vs at a frequency fs is provided on the measurement side. It is assumed that both the frequency fx and the frequency fs are known, and fs >> fx. A capacitance C1 exists between the measurement target and the measurement side. The capacity C1 may be unknown.

The current of the frequency fx flowing through the capacitance C1 due to the voltage Vx to be measured is defined as Ix, and the current of the frequency fs flowing through the capacitance C1 due to the voltage Vs of the variable voltage source 110 is defined as Is. In reality, the current obtained by superimposing the current Ix and the current Is will flow through the capacitance C1.

The measurement side is provided with a current detection unit 120, a difference extraction unit 130, a voltage adjustment unit 140, a voltage measurement unit 150, and a calculation unit 160. The grounding of the measurement target and the measurement side does not have to be common.

The current detection unit 120 detects the current in which the current Ix and the current Is are superimposed. The difference extraction unit 130 extracts and outputs a value corresponding to the difference between the magnitude of the current Ix and the magnitude of the current Is from the detection result of the current detection unit 120. The voltage adjusting unit 140 changes the output voltage Vs of the variable voltage source 110 so that the output of the difference extracting unit 130 becomes 0, that is, the magnitude of the current Is is equal to the magnitude of the current Ix. The voltage measuring unit 150 measures the output voltage Vs of the variable voltage source 110. The calculation unit 160 calculates and outputs the voltage Vx based on the measurement result of the voltage Vs in the voltage measurement unit 150.

ここで、Ａを定数としてｆｓ＝Ａ×ｆｘとすると、

が成り立つので、［数５］が得られる。

差分抽出部１３０と電圧調整部１４０により、Ｉｘ＝Ｉｓとなるように電圧Ｖｓが調整されるため、［数１］［数２］より、

そして、［数５］［数６］より［数７］が得られる。

したがって、演算部１６０は、電圧測定部１５０の測定結果ＶｓをＡ倍する演算を行なうことで、測定対象電圧Ｖｘを算出し、測定結果として出力することができる。例えば、測定対象電圧の周波数ｆｘを商用電源の５０Ｈｚとすると、測定側の周波数ｆｓが５０ｋＨであれば、電圧Ｖｓを１０００倍した値が測定対象の電圧Ｖｘとなる。すなわち、測定対象電圧が数ｋＶであっても数Ｖの電圧で測定できることになる。 In this configuration, assuming that the impedance of the capacitance C1 with respect to the current Ix is Xcx and the impedance of the capacitance C1 with respect to the current Is is Xcs, the current Ix and the current Is can be expressed as follows.

Here, if A is a constant and fs = A × fx, then

Therefore, [Equation 5] is obtained.

Since the voltage Vs is adjusted so that Ix = Is by the difference extraction unit 130 and the voltage adjustment unit 140, from [Equation 1] and [Equation 2],

Then, [Equation 7] is obtained from [Equation 5] and [Equation 6].

Therefore, the calculation unit 160 can calculate the measurement target voltage Vx and output it as the measurement result by performing an operation of multiplying the measurement result Vs of the voltage measurement unit 150 by A. For example, assuming that the frequency fx of the voltage to be measured is 50 Hz of the commercial power supply, if the frequency fs on the measurement side is 50 kHz, the value obtained by multiplying the voltage Vs by 1000 is the voltage Vx to be measured. That is, even if the measurement target voltage is several kV, it can be measured with a voltage of several V.

As described above, in the present invention, since the measurement side can measure at a voltage much lower than the voltage to be measured, expensive high withstand voltage components are not required for the components of the voltage measuring instrument. In addition, since high voltage is not generated inside the voltage measuring instrument, high insulation design and electric shock prevention measures are not required. Therefore, it is possible to prevent the cost increase as in the prior art, and it is possible to construct the voltage measuring instrument at low cost.

Next, an example of a voltage measuring instrument using the above measurement principle will be described. FIG. 2 is a diagram showing the configuration of the first embodiment of the voltage measuring instrument 100 of the present invention.

In the example of this figure, the measurement target is a conductor 310 to which a voltage of frequency fx and a voltage of Vx is applied. The conductor 310 is covered with an insulating coating 320 to form a coated electric wire 300.

The voltage measuring instrument 100 of the first embodiment includes an electrode 101, a current detection unit 120, a difference extraction unit 130, a voltage output unit 104, a voltage measuring unit 150, and a calculation unit 160.

The electrode 101 is attached to the covered electric wire 300. Therefore, the conductor 310 and the electrode 101 are not in contact with each other, and the parasitic capacitance C1 exists between the conductor 310 and the electrode 101.

The current detection unit 120 includes a resistor R121 and an instrumentation amplifier 122 that detects the voltage generated in the resistor R121.

The difference extraction unit 130 smoothes the frequency fx signal that has passed through the first filter unit 131 that passes the frequency fx signal, the second filter unit 132 that passes the frequency fs signal, and the first filter unit 131 to direct current. The first AC-DC conversion unit 133 to be converted, the second AC-DC conversion unit 134 that smoothes the signal of frequency fs that has passed through the second filter unit 132 and converts it to DC, and the first AC-DC conversion unit 133 output. The differential amplifier 135 for extracting the difference between the signal Vrx corresponding to the magnitude of the current Ix and the signal Vrs corresponding to the magnitude of the current Is output by the second AC-DC conversion unit 134 is provided.

The voltage output unit 104 includes a sinusoidal oscillator 111 having a frequency fs and a variable gain amplifier 141, and the voltage output unit 104 has the functions of the variable voltage source 110 and the voltage adjusting unit 140. The gain of the variable gain amplifier 141 is controlled by the output of the differential amplifier 135. Specifically, when Vrx> Vrs, the output voltage of the differential amplifier 135 increases, and the gain of the variable gain amplifier 141 increases. As a result, the amplitude of Vs increases and Vrs increases. On the other hand, when Vrx <Vrs, the output voltage of the differential amplifier 135 decreases, and the gain of the variable gain amplifier 141 decreases. As a result, the amplitude of Vs decreases and Vrs decreases. A multiplier may be used instead of the variable gain amplifier 141.

The voltage measuring unit 150 measures the output voltage Vs of the variable gain amplifier 141, and the calculation unit 160 calculates the voltage Vx based on the measurement result of the voltage Vs in the voltage measuring unit 150 and outputs it as the measurement result.

ｆｓ＝Ａ×ｆｘであるから、

となる。 In the first embodiment, since the resistor R121 is used for the current detection unit 120, the voltage drop Vrx due to the current Ix and the voltage drop Vrs due to the current Is generated in the resistor R121 are taken into consideration in the above [number 3] [number]. In addition to [4], [Equation 8] and [Equation 9] are obtained.

Since fs = A × fx,

Will be.

が得られる。－Ｖｒ^２は小さいので無視すると、

となる。さらに、抵抗Ｒ１２１が容量Ｃ１と周波数ｆｓとで決まるリアクタンスよりも十分小さければ、Ｖｒ^２を無視することができる。このため、電流検出用の抵抗Ｒ１２１を小さい値とすることで、Ｖｘ＝Ａ×Ｖｓが得られることになる。したがって、演算部１６０は、電圧測定部１５０の測定結果ＶｓをＡ倍する演算を行なうことで、測定対象電圧Ｖｘを算出し、出力することができる。もちろん、Ｖｒ（ＶｒｓあるいはＶｒｘ）を別途測定し、［数１２］にしたがって、測定対象電圧Ｖｘを算出し、出力してもよい。 Here, since the voltage Vs is adjusted by the difference extraction unit 130 and the voltage output unit 104 so that Ix = Is, Vrx and Vrs become equal, and if this is Vr, it is assumed.

Is obtained. -Vr ² is small, so if you ignore it,

Will be. Further, if the resistance R121 is sufficiently smaller than the reactance determined by the capacitance C1 and the frequency fs, ^Vr2 can be ignored. Therefore, by setting the resistance R121 for current detection to a small value, Vx = A × Vs can be obtained. Therefore, the calculation unit 160 can calculate and output the measurement target voltage Vx by performing an operation of multiplying the measurement result Vs of the voltage measurement unit 150 by A. Of course, Vr (Vrs or Vrx) may be measured separately, and the measurement target voltage Vx may be calculated and output according to [Equation 12].

The current detection unit 120 is composed of the resistor R121 and the instrumentation amplifier 122, but the present invention is not limited to this configuration, and various methods capable of acquiring a signal corresponding to the current can be adopted. For example, a hall sensor, a current transformer circuit, or the like may be used to detect a magnetic field due to a current and output a voltage proportional to the current. Further, a capacitor, a coil, or a combination thereof may be used instead of the resistor R121.

Further, as the first filter unit 131 and the second filter unit 132, the VCVS (salen key) type of the active bandpass filter, the multiple feedback type, the state variable type, the LC bandpass filter of the passive bandpass filter, and the RLC bandpass are used. Various methods such as a filter can be used.

Further, as the first AC-DC conversion unit 133 and the second AC-DC conversion unit 134, there are various types such as an RMS-DC converter (effective value detection), a full-wave average or half-wave average average value detection, and a peak hold circuit. Method can be used.

The sine wave oscillator 111 includes a crystal oscillator and a low-pass filter, a multi-vibrator and a low-pass filter, a Wien bridge type sine wave oscillator, an LC type sine wave oscillator, a two-phase type sine wave oscillator, a CR phase shift type sine wave oscillator, and a digital one. A direct synthesis oscillator (DDS) or the like can be used.

Next, a second embodiment of the voltage measuring instrument 100 of the present invention will be described with reference to FIG. In the second embodiment, the difference extraction unit 130 is configured by using a synchronous detection circuit. The synchronous detection circuit is a circuit that converts the magnitude of an input signal having the same frequency component as the reference signal into a DC voltage and outputs the signal.

In the example of this figure, the DC voltage Vrx corresponding to the magnitude of the signal of the frequency fx is obtained from the output signal of the current detection unit 120 by using the first synchronous detection unit 136, and the frequency is obtained by using the second synchronous detection unit 137. A DC voltage Vrs corresponding to the magnitude of the fs signal is obtained. The voltage measuring instrument 100 of the second embodiment includes a sinusoidal oscillator 138 having a frequency of fx for the reference signal of the first synchronous detection unit 136. As the reference signal of the second synchronous detection unit 137, the output signal of the sinusoidal oscillator 111 having a frequency fs is used.

Next, a third embodiment of the voltage measuring instrument 100 of the present invention will be described with reference to FIG. In the third embodiment, the digital signal processing unit 170 is provided, and processing other than the current detection unit 120 composed of the resistor R121 and the instrumentation amplifier 122 is performed by digital signal processing.

Therefore, the A / D conversion unit 177 for converting the output signal of the current detection unit 120 into digital data and the D / A that converts the output signal of the digital signal processing unit 170 into an analog signal having a frequency fs and a voltage value Vs. A conversion unit 178 is provided. The A / D conversion unit 177 can use various methods such as a flash type, a sequential comparison type, an integral type, and a delta sigma type. The D / A conversion unit 178 can use various methods such as a ladder type, a capacitive array type, and a current output type.

The digital signal processing unit 170 includes a frequency separator (fx) 171 that separates a signal of frequency fx and extracts Vrx, a frequency separator (fs) 172 that separates a signal of frequency fs and extracts Vrs, and Vrx. And Vrs are compared, and the level comparison unit 173 that changes the level control value based on the comparison result, the digital direct synthesis oscillator (DDS) 174 that outputs a sine wave of frequency fs as a digital signal, and the output and level of DDS174. It includes a multiplication unit 175 that multiplies the control value, and a calculation unit 176 that calculates and outputs the measurement target voltage Vx by performing an operation of multiplying the output of the multiplication unit 175 by the ratio of the frequency fs and the frequency fx. The frequency separators 171 and 172 can be configured by using a digital filter or a synchronous detection circuit.

Next, a fourth embodiment of the voltage measuring instrument 100 of the present invention will be described with reference to FIG. The fourth embodiment is a configuration that can be applied even when the exact frequency of the measurement target is not known. Although the description will be given based on the configuration of the first embodiment, it may be applied to other embodiments.

In the fourth embodiment, the frequency measuring unit 180 is used to measure the frequency of the signal that has passed through the first filter unit 131 to obtain an accurate frequency fx to be measured. The calculation unit calculates the measurement target voltage Vx by multiplying the measurement result of the voltage measurement unit 150 by the ratio of the frequency fs and the frequency fx. The first filter unit 131 uses a filter that includes the approximate frequency of the measurement target in the pass band.

The frequency measuring unit 180 can use various methods. For example, a method of measuring the number of times the input signal and the reference voltage intersect in a fixed measurement time, a method of measuring the time (cycle) at which the input signal and the reference voltage intersect, and the like can be used.

Next, a fifth embodiment of the voltage measuring instrument 100 of the present invention will be described with reference to FIG. The fifth embodiment has a configuration in which the voltage can be measured not only in the non-contact state with the measurement target but also in the contact state. Although the description will be given based on the configuration of the first embodiment, it may be applied to other embodiments.

In the voltage measuring instrument 100 of the fifth embodiment, an actual capacitor 102 is connected between the electrode 101 and the current detection unit 120. Therefore, even when the electrode 101 is in contact with the conducting wire 330, the capacitor 102 plays the role of the capacitance C1, so that the measurement target voltage Vx can be measured. Further, when measuring the coated electric wire 300, since the parasitic capacitance and the combined capacitance of the capacitor 102 play the role of the capacitance C1, the measurement target voltage Vx can be measured. That is, the measurement target voltage Vx can be measured both in non-contact and in contact.

By the way, the voltage Vx to be measured may include noise having a peak at a specific frequency such as inverter noise in addition to the fundamental frequency fx component. Assuming that the frequency of this noise and the frequency fs of the variable voltage source 110 match, the current Is detected by the current detection unit 120 includes the current caused by the noise. As a result, the voltage Vs of the variable voltage source 110 is affected by noise, and as a result, an error may occur in the measured voltage.

In order to prevent this error, measurement is performed using a plurality of different values as the frequency fs of the variable voltage source 110, and the measurement target voltage Vx is comprehensively calculated based on the measured voltage Vx for each obtained frequency. Can be considered. As a result, even if a measured voltage affected by noise is obtained at a certain frequency, a measured voltage unaffected by noise can be obtained at other frequencies. Therefore, it is possible to prevent an error due to noise by performing operations such as adding and averaging the measured voltages for each frequency and extracting the median value.

Therefore, the measurement principle of the voltage measuring instrument according to the second embodiment of the present invention, which can prevent an error due to noise, will be described with reference to FIG. 7. As shown in this figure, the voltage measuring instrument of the second embodiment has a variable voltage source 110, a current detecting unit 120, a difference extracting unit 130, a voltage adjusting unit 140, a voltage measuring unit 150, and a measuring unit 200 having a calculation unit 160. Are connected in parallel (200a, 200b, ...), And the outputs of the respective arithmetic units (160a, 160b, ...) Are input to the general arithmetic unit 161. In addition, each arithmetic unit (160a, 160b, ...) may be included in the general arithmetic unit 161.

The variable voltage source 110, the current detection unit 120, the difference extraction unit 130, the voltage adjustment unit 140, the voltage measurement unit 150, and the calculation unit 160 included in each measurement unit 200 can be the same as those in the above-described embodiment.

However, in the voltage measuring instrument of the second embodiment, the variable voltage sources (110a, 110b, ...) Of each measuring unit (200a, 200b, ...) Have different unique frequencies (fsa, fsb, ...) AC. Output voltage. It is assumed that the inherent frequencies are sufficiently larger than the frequency fx. Then, the calculation unit (160a, 160b, ...) Of each measurement unit (200a, 200b, ...) Individually calculates the measurement voltage (Vxa, Vxb, ...). The calculation principle of the measured voltage (Vxa, Vxb, ...) Is the same as that of the above-described embodiment.

The individual measurement voltages (Vxa, Vxb, ...) May be measured simultaneously by each measuring unit (200a, 200b, ...) Or may be sequentially performed.

In the second embodiment, the measurement target voltage Vx is comprehensively calculated based on the individually calculated measured voltages (Vxa, Vxb, ...). Specifically, the total calculation unit 161 calculates the measurement target voltage Vx by performing calculations such as adding and averaging individually calculated measured voltages (Vxa, Vxb, ...) And extracting the median value.

Next, a voltage measuring instrument according to a third embodiment of the present invention, which can prevent an error due to noise as in the second embodiment, will be described with reference to FIG. In the voltage measuring instrument shown in FIG. 1, the voltage measuring instrument of the third embodiment uses a variable voltage source 190 whose frequency can be switched in a time division instead of the variable voltage source 110 having a fixed frequency. Further, it is provided with a comprehensive calculation unit 162 that stores the output of the calculation unit 160 for each frequency and performs calculations such as addition averaging and extraction of the median value.

In the voltage measuring instrument of the third embodiment, the frequency fs of the variable voltage source 190 is switched by time division to perform a plurality of measurements. The frequency fs can be switched, for example, based on the control of the total calculation unit 162. In each measurement, the calculation unit 160 calculates the measured voltage in the same manner as in the above-described embodiment, and outputs the calculation to the total calculation unit 162. It is assumed that the frequency fs to be switched is sufficiently larger than the frequency fx.

The total calculation unit 162 stores the calculation result of the calculation unit 160 at each frequency, and calculates the measurement target voltage Vx by performing calculations such as adding and averaging the stored measured voltages and extracting the median value. This makes it possible to prevent errors caused by noise.

In both the second embodiment and the third embodiment, any of the above-mentioned first to fifth embodiments may be applied to the specific circuit configuration.

100 Voltage measuring instrument 101 Electrode 102 Capacitor 104 Voltage output unit 110 Variable voltage source 111 Sine and cosine oscillator 120 Current detector 121 Resistance R
122 Instrumentation amplifier 130 Difference extraction unit 131 1st filter unit 132 2nd filter unit 133 1st AC-DC conversion unit 134 2nd AC-DC conversion unit 135 Differential amplifier 136 1st synchronous detection unit 137 2nd synchronous detection unit 138 Sine wave oscillator 140 Voltage adjustment unit 141 Variable gain amplifier 150 Voltage measurement unit 160 Calculation unit 161 Comprehensive calculation unit 162 Comprehensive calculation unit 170 Digital signal processing unit 171 Frequency separator 173 Level comparison unit 175 Multiplication unit 176 Calculation unit 177 A / D Conversion unit 178 D / A conversion unit 180 Frequency measurement unit 190 Variable voltage source 300 Coated wire 310 Conductor 320 Insulation coated 330 Conductor

Claims (7)

A voltage measuring device that measures the AC voltage of the first frequency applied to the conductor .
An electrode attached to the conductor via a capacitance and
A variable voltage source that is connected to the electrode and outputs an AC voltage of the second frequency,
A current detection unit that detects the current flowing between the electrode and the variable voltage source, and
A difference extraction unit that extracts and outputs a value corresponding to the difference between the magnitude of the first frequency component and the magnitude of the second frequency component from the detected current, and a difference extraction unit.
A voltage adjusting unit that changes the output voltage of the variable voltage source so that the output of the difference extraction unit becomes 0.
An arithmetic unit that calculates the AC voltage of the first frequency based on the output voltage of the variable voltage source, the first frequency, and the second frequency.
A voltage measuring device characterized by being equipped with. The first aspect of claim 1, wherein the arithmetic unit calculates an AC voltage of the first frequency by multiplying the ratio of the second frequency to the first frequency by the output voltage of the variable voltage source. Voltage measuring device. The voltage measuring device according to claim 1 or 2, wherein the electrode and the variable voltage source are connected via a capacitor. A voltage measuring device that measures the AC voltage of the first frequency applied to the conductor .
An electrode attached to the conductor via a capacitance and
With multiple measuring units
Equipped with a comprehensive calculation unit,
The measuring unit
A variable voltage source that is connected to the electrodes and outputs an AC voltage with a unique frequency that is different for each measuring unit .
A current detection unit that detects the current flowing between the electrode and the variable voltage source, and
A difference extraction unit that extracts and outputs a value corresponding to the difference between the magnitude of the first frequency component and the magnitude of the unique frequency component from the detected current, and a difference extraction unit.
A voltage adjusting unit that changes the output voltage of the variable voltage source so that the output of the difference extraction unit becomes 0.
A calculation unit that calculates an AC voltage of the first frequency based on the output voltage of the variable voltage source and the first frequency and the inherent frequency is provided.
The general calculation unit is
A voltage measuring device characterized in that the AC voltage of the first frequency is calculated based on the AC voltage of the first frequency calculated for each measuring unit. A voltage measuring device that measures the AC voltage of the first frequency applied to the conductor .
An electrode attached to the conductor via a capacitance and
A variable voltage source that is connected to the electrode and outputs a switchable second frequency AC voltage,
A current detection unit that detects the current flowing between the electrode and the variable voltage source, and
A difference extraction unit that extracts and outputs a value corresponding to the difference between the magnitude of the first frequency component and the magnitude of the second frequency component from the detected current, and a difference extraction unit.
A voltage adjusting unit that changes the output voltage of the variable voltage source so that the output of the difference extraction unit becomes 0.
A calculation unit that calculates the AC voltage of the first frequency based on the output voltage of the variable voltage source, the first frequency, and the second frequency for each of the switched second frequencies.
A general calculation unit that calculates the AC voltage of the first frequency based on the AC voltage of the first frequency calculated for each second frequency , and
A voltage measuring device characterized by being equipped with. It is a voltage measuring method for measuring the AC voltage of the first frequency.
Regarding the current flowing through the capacitance when the second frequency AC voltage is applied from the electrodes attached via the capacitance to the measurement object to which the first frequency AC voltage is applied.
The magnitude of the AC voltage of the second frequency is adjusted so that the magnitude of the first frequency component and the magnitude of the second frequency component are the same .
A voltage measuring method characterized in that an AC voltage of the first frequency is calculated based on the AC voltage of the second frequency, the first frequency, and the second frequency at that time. It is a voltage measuring method for measuring the AC voltage of the first frequency.
Regarding the current flowing through the capacitance when the AC voltage of the second frequency, which can be switched from the electrodes attached via the capacitance, is applied to the measurement object to which the AC voltage of the first frequency is applied.
The magnitude of the AC voltage of the second frequency is adjusted so that the magnitude of the first frequency component and the magnitude of the second frequency component are the same for each of the switched second frequencies . The AC voltage of the first frequency is calculated based on the AC voltage of the second frequency, the first frequency, and the second frequency.
A voltage measuring method comprising calculating the AC voltage of the first frequency based on the calculated AC voltage of the first frequency for each second frequency.

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