JP6502072B2 - Voltage detection device - Google Patents

Description

  The present invention relates to a noncontact voltage detection device that detects a voltage of a detection target covered with an insulating material through the insulating material.

  As a noncontact voltage detection device, a voltage detection device (noncontact static voltage follower) disclosed in Patent Document 1 below is known. The voltage detection device includes a probe for voltage detection. This probe is operatively connected to a detection electrode which is arranged towards the measurement surface (surface to be detected) with the amount of electrostatic charge to be measured, and to detect the capacitive coupling between the detection electrode and the measurement surface A modulator or drive means and means for defining the path of radiation directed to the measurement surface to illuminate the area of the measurement surface coincident with the detection electrode.

  Also, the detection electrode is accommodated in the housing. The housing is also provided with a first opening or window through which the detection electrode is exposed to the measurement surface. The detection electrode is also connected by a wire to the summing input (inverting input) of an amplifier (operational amplifier for current-voltage conversion) contained in the housing, the non-inverting input of this amplifier being connected by a line to the reference unit Connected to the housing. In addition, for example, a piezoelectric transducer can be used as the modulator or drive means, and the modulator or drive means mechanically moves (vibrates) the detection electrodes connected in operation to obtain the measurement surface and the detection electrodes. Modulate the capacitance (coupling capacitance) formed between

  In the voltage detection device provided with this probe, when modulating this capacitance, the current flows through the capacitance and a resistor connected between the summing input end (inverting input end) of the amplifier and the output terminal for current-voltage conversion. Based on the current, it is possible to contactlessly detect the voltage of the measuring surface.

Japanese Examined Patent Publication No. 7-92487 (page 6, FIG. 7)

  However, the above-described voltage detection device has the following problems to be solved. That is, in this voltage detection device, it is necessary to arrange the probe on the measurement surface so that the detection electrode is exposed to the measurement surface through the first opening (or window) provided in the housing. This is because, if the first opening is covered with an insulator, charges appear theoretically on the surface of the insulator under the influence of the voltage of the measurement surface, but charges appearing on the surface of the insulator easily escape Disappear. Therefore, in this voltage detection device, there is a problem to be solved that when the insulator is interposed between the measurement surface and the detection electrode, the voltage of the measurement surface can not be detected.

  The present invention has been made to solve such a problem, and is a voltage detection that can detect the voltage of a detection object without contact even when an insulator is present between the detection object and the detection electrode. The main purpose is to provide a device.

  In order to achieve the above object, a voltage detection device according to claim 1 is a voltage detection device for detecting a voltage to be detected occurring in a detection object covered with an insulator, wherein the voltage detection device is directly or otherwise connected to the insulator. By applying a static magnetic field to a detection electrode disposed indirectly in contact with an insulator and the detection target while applying a static magnetic field to the detection target, an eddy current is generated at a site to which the static magnetic field is applied in the detection target. An ultrasonic excitation unit configured to excite an ultrasonic wave vibrating in a direction crossing the surface of the application site to the detection target; and a state in which the ultrasonic wave is excited on the detection target, the detection electrode to the detection electrode A current-voltage variation that converts a detection current synchronized with the ultrasonic wave, which flows into the reference voltage via the reference voltage and is modulated in amplitude according to the potential difference between the detection target voltage and the reference voltage, into a detection voltage signal And a detection circuit for detecting the circuit, the detection output indicative of the potential difference from the detected voltage signal.

  In the voltage detection device according to claim 2, in the voltage detection device according to claim 1, the ultrasonic excitation unit generates the static magnetic field and applies the static magnetic field to the detection target to generate the static magnetic field. A magnet for generating a static magnetic field along the surface and a coil for generating the eddy current in the detection object based on the supplied alternating current are provided to be orthogonal to the surface of the application site The ultrasonic waves oscillating in a direction are excited.

  The voltage detection apparatus according to claim 3 is the voltage detection apparatus according to claim 2, wherein the magnet is a first magnet in which the coil is disposed in the vicinity of the magnetic pole on the application site side, and the respective application sites. The magnetic pole on the side is magnetized with a polarity different from that of the magnetic pole of the first magnet, and is provided with a second magnet and a third magnet disposed so as to sandwich the magnetic pole of the first magnet.

  The voltage detection device according to claim 4 is the voltage detection device according to any one of claims 1 to 3, wherein the detection circuit synchronously detects the detection voltage signal with a synchronization signal synchronized with the detection voltage signal. The detection output is detected.

  The voltage detection device according to claim 5 is the voltage detection device according to any one of claims 1 to 4, wherein in the current-voltage conversion circuit, a first input terminal is defined to the reference voltage, and a second input The operational amplifier has a terminal connected to the detection electrode and a feedback circuit connected between the second input terminal and the output terminal to convert the detection current flowing in the feedback circuit into the detection voltage signal. doing.

  In the voltage detection device according to claim 1, the ultrasonic excitation unit excites the ultrasonic wave inside the detection object to generate a vibration in the detection object, and an insulator in which the detection electrode is brought into contact with the generated vibration. By vibrating, a detection current is generated, and a detection target voltage to be detected is detected based on the detection current. Therefore, according to this voltage detection device, even when the insulator is present between the detection target and the detection electrode, the detection target voltage is not in contact (without bringing the detection electrode into direct contact with the detection target) It can be detected.

  In the voltage detection device according to claim 2, the ultrasonic excitation unit is based on a magnet that generates a static magnetic field along the surface of the application site within the application site of the static magnetic field in the detection target, and the supplied alternating current. And a coil for generating an eddy current in the detection target, and an ultrasonic wave vibrating in a direction (depth direction in the detection target) orthogonal to the surface of the application site is excited in the detection target. Therefore, according to this voltage detection device, the vibration in the direction in which the capacitance value of the capacitance of the insulator can be most efficiently changed can be generated on the detection target and the insulator, so the detection target passes through the detection electrode. As a result, the level of the detection current flowing to the reference potential can be increased, and the detection sensitivity of the voltage to be detected can be sufficiently enhanced.

  According to the voltage detection device of the third aspect, the static magnetic field along the surface of the detection target inside both sides of the opposing portion with respect to the opposing portion to the magnetic pole of the central first magnet in the applying portion of the static magnetic field. As a result, more static magnetic fields can be applied to the eddy current generated around the opposing part, and thus stronger ultrasonic waves and thus stronger vibrations are generated inside the detection target. be able to. As a result, according to this voltage detection device, the level of the detection current flowing from the detection target to the reference potential via the detection electrode can be further increased. As a result, the detection sensitivity of the detection target voltage can be further improved.

  According to the voltage detection device of the fourth aspect, the detection circuit synchronously detects the detection voltage signal with the synchronization signal and outputs the detection output, so that the detection output can be detected with less influence of the disturbance.

  According to the voltage detection device of the fifth aspect, the current-voltage conversion circuit includes the operational amplifier and the feedback resistor, so that the detection current can be detected with high sensitivity and converted into a detection voltage signal.

FIG. 2 is a block diagram of a voltage detection device 1; 5 is a perspective view of a detection electrode 11 and an ultrasonic excitation unit 13. FIG. FIG. 6 is an explanatory diagram for explaining an operation of the voltage detection device 1; It is explanatory drawing for demonstrating the structure of 13 A of ultrasonic wave excitation parts. It is explanatory drawing for demonstrating the structure of the ultrasonic excitation part 13B.

  Hereinafter, embodiments of a voltage detection device will be described with reference to the attached drawings.

  First, the configuration of the voltage detection device will be described with reference to the drawings.

  The voltage detection device 1 as the voltage detection device shown in FIG. 1 is a non-contact voltage detection device, and as an example, the detection electrode 11, the oscillation circuit 12, the ultrasonic excitation unit 13, the current voltage conversion circuit 14, and the buffer The amplifier 15, the detection circuit 16, the phase adjustment circuit 17 and the output circuit 18 are provided, and the voltage (detection target voltage) V1 generated in the detection target 52 covered with the insulator 51 can be detected without contact. .

  In this case, the detection target 52 is a conductor, and as shown in FIGS. 1 and 3, a part of the surface may be covered with an insulator 51, as shown in FIG. The entire surface may be covered with the insulator 51 (for example, the detection target 52 may be a core wire of a covered electric wire in which the entire outer peripheral surface is covered with the insulating coating). In addition, the insulator 51 may have a single-layer structure formed of one type of insulating material, or a multilayer structure in which a plurality of layers formed of different types of insulating materials are stacked. Good.

  The detection electrode 11 is disposed so as to be in direct contact with the surface of the insulator 51 covering the detection target 52 by the configuration described later.

  The oscillator circuit 12 generates and outputs a reference signal S1 having a constant frequency (predetermined frequency) of, for example, several tens of kHz (a frequency exceeding the audible range) to several MHz. In this case, the oscillation circuit 12 can adopt a configuration in which the reference signal S1 is continuously output during operation, or a configuration in which the reference signal S1 is intermittently output periodically and periodically. It is also possible to adopt a configuration in which the output is made only once for a fixed time only at the time of measurement. The oscillation circuit 12 also outputs, for example, one of a rectangular wave signal, a triangular wave signal, and a sine wave signal as a reference signal S1. Note that, instead of the configuration in which the oscillation circuit 12 generates and outputs the reference signal S1 at a constant frequency as described above, for example, the frequency changes with time within the range of the lower limit frequency and the upper limit frequency defined in advance. A configuration in which the reference signal S1 is generated and output as a sweep signal or a configuration in which the reference signal S1 is generated and output as a random signal (noise signal) whose frequency changes randomly with time can be adopted.

  As shown in FIG. 1, the ultrasonic excitation unit 13 applies a static magnetic field M to the detection target 52, and generates an eddy current Ied at the application site of the static magnetic field M in the detection target 52, thereby An ultrasonic wave US vibrating in a direction (depth direction) intersecting the surface is excited inside the detection object 52. In this example, as an example, as shown in FIGS. 2 and 3, the ultrasonic excitation unit 13 generates a static magnetic field M and applies it to the detection target 52 to generate an applied portion within the application target in the detection target 52. The magnet 21 generates a static magnetic field M along the surface, the current source circuit 22 generates an alternating current Iac having the same frequency as the reference signal S1 based on the reference signal S1, and the supply of the alternating current Iac from the current source circuit 22 The coil 23 is provided to generate an eddy current Ied at the application site (surface of the application site) of the object 52 to be detected.

  In this example, the magnets 21 are each formed in a columnar body (a columnar body, a polygonal prism such as a quadrangular prism, etc. In this example, a quadrangular prism as an example), and both ends as magnetic poles are attached to different poles. Three magnetized magnets (permanent magnets as an example in this example) 21a, 21b, 21c (a magnet 21a as a second magnet, a magnet 21b as a first magnet, and a magnet 21c as a third magnet) are provided. The magnets 21a, 21b, 21c are arranged in a line with the insulator 24 interposed. Further, the polarity of the same one side end (one end; the upper end in FIG. 1 and the end on the application site side) of each magnet 21a, 21b, 21c is the same as that of the central magnet 21b. The polarity (N pole in this example) is different from the polarity of the other two magnets (magnets on both sides) 21 a and 21 c (S pole in this example).

  In addition, each magnet 21a, 21b, 21c can also be comprised with an electromagnet instead of a permanent magnet. Also, instead of the configuration in which the two separately formed magnets 21a and 21c are disposed on both sides of the central magnet 21b (the configuration in which the two magnets 21a and 21c are disposed to sandwich the central magnet 21b), Although not shown, only one of the two magnets 21a and 21c is disposed on one side of the central magnet 21b, or the two magnets 21a and 21c are formed as one cylindrical magnet, and this cylinder It is also possible to adopt a configuration in which the magnet 21b is disposed on the axis of the magnet.

  Further, in the present embodiment, as an example, the magnets 21a and 21c on both sides are configured such that the end faces of one end of each of the magnets 21a and 21c are positioned in the same virtual plane W. Further, the end face of one end (upper end in the same figure) of the central magnet 21b and the insulator 24 located on both sides of the central magnet 21b is one end of the imaginary plane W (both magnets 21a and 21c) It is configured to be recessed by approximately the same length with respect to the end face of the portion). With this configuration, a recess A of substantially constant depth is formed between one end of each of the magnets 21a and 21c on both sides.

  The coil 23 is, for example, configured as an annular flat coil and disposed near one end of the magnet 21 b. Specifically, the coil 23 is in the vicinity of one end of the magnet 21b and is a recess in which the end face of the one end of the magnet 21b is wound from the central portion (a hole formed at the center of the coil 23). It is disposed at a position in A and parallel to the virtual plane W.

  Further, in the present embodiment, as an example, the detection electrode 11 is disposed in the state where the insulator 25 is interposed on the end face of one end of the central magnet 21b. The detection electrode 11 has its surface (the upper surface of the detection electrode 11 in FIGS. 2 and 3) by adjusting at least one of the depth of the recess A, the thickness of the insulator 25 and the thickness of the detection electrode 11. Is positioned in the virtual plane W or in a state slightly protruding from the virtual plane W (in the present example, the former state as an example).

  With this configuration, in the voltage detection device 1, the ultrasonic excitation unit 13 is brought into contact with the insulator 51 from one end side of each of the magnets 21 a, 21 b and 21 c so that the detection electrode 11 is the surface of the insulator 51. It is possible to make direct contact with That is, the ultrasonic excitation unit 13 has a configuration in which the magnets 21a, 21b, 21c are arranged vertically with respect to the insulator 51 (that is, with respect to the application site of the detection target 52). .

  As one example, the current-voltage conversion circuit 14 is configured to include an operational amplifier 14a and a feedback resistor 14b as a feedback circuit. In the operational amplifier 14a, the non-inverted input terminal (first input terminal) is connected to the reference potential (ground) to be defined as the reference voltage (zero volt), and the inverted input terminal (second input terminal) is connected to the detection electrode 11 A feedback resistor 14 b is connected between the inverting input terminal and the output terminal. In this example, as one example, the feedback circuit is configured by one feedback resistor 14b, but the feedback circuit is configured by a series or parallel circuit of a plurality of resistors, or a series / parallel circuit combining a series circuit and a parallel circuit. It can also be configured.

  The current-voltage conversion circuit 14 is provided between the detection object 52 and the detection electrode 11 due to the vibration generated in the detection object 52 based on the ultrasonic wave US generated in the detection object 52 by the ultrasonic excitation unit 13. When the capacitance value of the electrostatic capacitance of the insulator 51 located is changing, the voltage V1 of the detection object 52 and the voltage of the detection electrode 11 (the input terminals of the operational amplifier 14a are in a virtual short state, so the reference voltage ) And the current value (amplitude) corresponding to the magnitude of the potential difference Vdi from the detection object 52 via the detection electrode 11 due to the potential difference Vdi with (in this example, the reference voltage is zero volts and hence the voltage V1). The detection current I flowing to the reference potential is converted into a detection voltage signal V2 and output. That is, in this current-voltage conversion circuit 14, the detection current I whose amplitude is modulated in accordance with the potential difference between the voltage V1 of the detection object 52 and the voltage (reference voltage) of the detection electrode 11 Current) synchronized to the detection voltage signal V2.

  In this case, the detection current I is the frequency of the vibration generated in the detection object 52 (that is, the frequency of the ultrasonic wave US, that is, the same frequency as each frequency of the alternating current Iac and the reference signal S1. Hereinafter, also referred to as “vibration frequency”) Is generated due to a change in the capacitance value of the capacitance of the insulator 51, so that it is an AC signal of the same frequency as the vibration frequency, and the amplitude thereof is the above-mentioned potential difference Vdi (voltage V1 in this example). It is generated as an alternating current signal modulated to a corresponding level. For this reason, the detection voltage signal V2 is also an AC signal having the same frequency as the vibration frequency, and the current / voltage conversion circuit 14 is an AC signal whose amplitude is modulated to a level corresponding to the potential difference Vdi (voltage V1 in this example). Output from

  The current-voltage conversion circuit 14 has a configuration including the operational amplifier 14a and the feedback resistor 14b as described above as an example, and generally detects the detection current I with extremely small (weak) amplitude with high sensitivity. Although the voltage signal V2 can be converted, it is not limited thereto. For example, when it is desired to realize the current-voltage conversion circuit 14 with a simpler configuration, instead of the above configuration, one end is connected to the detection electrode 11 and the other end is a reference potential, although not shown. It is also possible to employ a configuration having a resistor connected to (ground). In the current-voltage conversion circuit 14 of this configuration, the resistor converts the detection current I flowing from the detection target 52 to the reference potential (reference voltage) via the detection electrode 11 into the detection voltage signal V2. Then, a detection voltage signal V2 converted at one end of this resistor is output to a buffer amplifier 15 described later.

  The buffer amplifier 15 is formed of an amplifier with a high input impedance and a low output impedance, receives the detection voltage signal V2 output from the current-voltage conversion circuit 14, and outputs the detection voltage signal V2 with a low impedance. The detection circuit 16 is formed of, for example, a synchronous detection circuit, and synchronously detects the detection voltage signal V2 input from the buffer amplifier 15 with the synchronization signal S2 input from the phase adjustment circuit 17 to obtain the amplitude of the detection voltage signal V2. The component (DC component) is detected (extracted) and output as a detection output (voltage signal) V3. The detection circuit 16 is configured by any one of a multiplier, a changeover switch (multiplexer) configured by an analog switch, and a correlator. The detection circuit 16 can also be configured as an envelope detection circuit, and when this configuration is adopted, the synchronization signal S2 becomes unnecessary, so the phase adjustment circuit 17 can be omitted.

  The phase adjustment circuit 17 inputs and delays the reference signal S1 from the oscillation circuit 12 and outputs it as a synchronization signal S2. The phase adjustment circuit 17 is configured to be able to adjust the delay amount of the synchronization signal S2 with respect to the reference signal S1. The delay amount is adjusted in advance so that the phase of the detection voltage signal V2 as an AC signal input to the detection circuit 16 and the phase of the synchronization signal S2 coincide with each other.

  The output circuit 18 detects, for example, a voltage value of the detection output V3 and displays it, a buffer circuit which receives the detection output V3 and outputs it at low impedance, and A / D converts the detection output V3 It comprises an A / D converter or the like that outputs voltage data indicating a voltage value.

  Next, an operation of detecting the voltage V1 of the detection target 52 by the voltage detection device 1 will be described. The voltage V1 may be a direct current voltage or an alternating current voltage. In this example, as an example, the voltage V1 is a DC voltage.

  First, as shown in FIGS. 1 and 3, bringing the end face of one end of each of the magnets 21a and 21c constituting the ultrasonic excitation unit 13 into contact with the surface of the insulator 51 covering the detection object 52 Thus, the detection electrodes 11 located in the same imaginary plane W as the end faces are brought into contact (intimately contact) with the surface of the insulator 51. At this time, in order to improve the adhesion between the insulator 51 and the detection electrode 11, another insulator (for example, an insulating sheet or a gel-like insulator) may be interposed between these members. .

  As a result, as shown in FIG. 3, static electricity is generated between one end of each of the pair of magnets 21a, 21b of the magnets 21a, 21b, 21c (between the ends magnetized to different polarities). A static magnetic field M generated between one end of each of the magnetic field M and the other pair of magnets 21 b and 21 c (between the ends magnetized to different polarities) of the detection object 52 via the insulator 51 It is applied to the application site. In this case, one end of each of the pair of magnets 21a and 21b is arranged along the surface of the insulator 51 (also "along the surface of the detection object 52"), and the pair of magnets 21b , 21c, as shown in the figure, because each one of the end portions is also arranged along the surface of the insulator 51 (also along the surface of the detection object 52). The static magnetic field M inside the application site in the object 52 is generated in the direction along the surface of the application site.

  Further, in the ultrasonic excitation unit 13, the magnets 21a and 21c (a magnet separate from the magnet 21b) have a polarity of one end different from that of one end of the magnet 21b with respect to the magnet 21b. Since the respective one end portions are arranged to be close to each other, it is possible to generate a strong static magnetic field M inside the detection target 52.

  In this state, when the reference signal S1 is output from the oscillation circuit 12, in the ultrasonic excitation unit 13, the current source circuit 22 generates an alternating current Iac based on the reference signal S1 and supplies it to the coil 23. The coil 23 receives the supply of the alternating current Iac to generate an alternating magnetic field (not shown). The coil 23 is disposed in parallel with the imaginary plane W in the recess A formed between the ends of the magnets 21a and 21c on both sides as described above. Therefore, the alternating magnetic field generated in the coil 23 is applied to the surface of the detection target 52 to which the static magnetic field M is applied. Due to the alternating magnetic field, an eddy current Ied is generated on the surface of the application site in the detection target 52.

  Thus, since the eddy current Ied is generated on the surface of the portion to which the static magnetic field M is applied in the detection target 52 (the portion where the static magnetic field M is generated in the direction along the surface of the detection target 52) Based on the magnetic field M and the eddy current Ied, as shown by the white arrows, the direction (the depth direction of the detection object 52, that is, the application region of the detection object 52 intersects the surface of the detection object 52). Lorentz force F is generated along the direction orthogonal to the surface). Since the direction of the Lorentz force F is reversed every half cycle of the alternating current Iac, a direction crossing the surface of the application site on the basis of the Lorentz force F is detected inside the detection object 52 (detection object 52 The ultrasonic wave US having the same frequency as the alternating current Iac is excited along the depth direction of Further, due to the generation of the ultrasonic wave US, in the detection object 52, vibration in a direction (depth direction of the detection object 52) intersecting with the surface of the application site is generated at the same frequency as the alternating current Iac. .

  Since this vibration (mechanical vibration) is transmitted to the insulator 51 in contact with the detection target 52, the insulator 51 also vibrates at the same frequency (vibration frequency) as the detection target 52. In this case, the distance or density (density of the insulator 51) between the detection object 52 and the detection electrode 11 changes at the same frequency as the vibration frequency of the insulator 51 (also the vibration frequency of the detection object 52). The capacitance value of the capacitance of the insulator 51 located between the object 52 and the detection electrode 11 also changes at the same frequency as this vibration frequency. Further, as the capacitance value of this capacitance changes, the amplitude is modulated to a level according to the potential difference Vdi (voltage V1), and the detection current I which is an AC signal having the same frequency as the vibration frequency is a detection target 52, flows in a path including the detection electrode 11 and the feedback resistor 14b of the current-voltage conversion circuit 14.

  The current-voltage conversion circuit 14 converts the detection current I into a detection voltage signal V2 and outputs it, and the buffer amplifier 15 receives the detection voltage signal V2 output from the current-voltage conversion circuit 14 and outputs it at low impedance. Do. On the other hand, the phase adjustment circuit 17 outputs the synchronization signal S2 to the detection circuit 16 by inputting and delaying the reference signal S1.

  The detection circuit 16 performs a synchronous detection of the detection voltage signal V2 output from the buffer amplifier 15 with the synchronization signal S2 output from the phase adjustment circuit 17, thereby disturbing the amplitude component (DC component) of the detection voltage signal V2. Is detected in a state where the influence of V.sub.2 is small and is output to the output circuit 18 as a detection output (voltage signal) V3. In this case, the amplitude component (DC component) of the detection voltage signal V2 detected as the detection output V3 changes in level in accordance with the above-described potential difference Vdi (voltage V1 in this example).

  The output circuit 18 receives the detection output (voltage signal) V3. When the output circuit 18 is constituted by, for example, an analog voltmeter, the voltage value of the detection output V3 (a voltage value proportional to the potential difference Vdi (voltage V1)) Based on this, by moving the pointer to a value indicating the voltage value of the potential difference Vdi (voltage V1), the voltage value of the potential difference Vdi (voltage V1) is output in a visually recognizable state. In addition, when the output circuit 18 is formed of, for example, a buffer circuit, the detection output V3 is input and output to the outside with a low impedance (for the external measuring instrument or the like, a potential difference is generated based on the detection output V3). Output so that the voltage value of Vdi (voltage V1) can be detected). Further, when the output circuit 18 is formed of, for example, an A / D converter, voltage data indicating the voltage value of the detection output V3 is also input (voltage data indicating the voltage value of the potential difference Vdi (voltage V1)). Output) to a processing unit (not shown) provided inside or an external processing device.

  As described above, in the voltage detection device 1, the ultrasonic excitation unit 13 excites the ultrasonic wave US inside the detection target 52 to cause the detection target 52 to vibrate, and the generated vibration causes the detection electrode 11 to be detected. By vibrating the insulator 51 brought into contact, the detection current I is generated, and the voltage V1 of the detection target 52 is detected based on the detection current I. Therefore, according to the voltage detection device 1, even when the insulator 51 is present between the detection target 52 and the detection electrode 11, the voltage V1 of the detection target 52 is not detected in a non-contact manner (detection of the detection electrode 11 Can be detected without direct contact with the object 52).

  Further, in the voltage detection device 1, the ultrasonic excitation unit 13 is supplied with the magnet 21 for generating the static magnetic field M along the surface of the application site inside the application site of the static magnetic field M in the detection object 52 A coil 23 for generating an eddy current Ied in a detection object 52 based on an alternating current Iac, and detects an ultrasonic wave US vibrating in a direction (depth direction of the detection object 52) orthogonal to the surface of the application site It excites into the object 52. Therefore, according to this voltage detection device 1, it is possible to cause the detection object 52 and the insulator 51 to generate the vibration in the direction in which the capacitance value of the capacitance of the insulator 51 can be most efficiently changed. As a result, it is possible to increase the level of the detection current I flowing to the reference potential via the detection electrode 11, so that the detection sensitivity of the voltage V1 of the detection target 52 can be sufficiently enhanced.

  Further, in the voltage detection device 1, the magnet 21 is a central magnet 21b in which the coil 23 is disposed in the vicinity of one end as a magnetic pole at the application site side, and one as a magnetic pole at each application site. And the two magnets 21a and 21c disposed on both sides of the magnet 21b so as to sandwich one end of the magnet 21b. There is.

  Therefore, according to the voltage detection device 1, the surface of the detection target 52 is internally provided on both sides of the opposing portion with respect to the opposing portion to the one end of the central magnet 21 b in the application portion of the static magnetic field M. Since the static magnetic field M can be generated, more static magnetic field M can be applied to the eddy current Ied generated around the opposing portion, resulting in stronger ultrasonic waves US and hence stronger vibrations. It can be generated inside the detection object 52. As a result, according to the voltage detection device 1, the level of the detection current I flowing from the detection object 52 to the reference potential via the detection electrode 11 can be further increased. As a result, the detection sensitivity of the voltage V1 of the detection object 52 It can be further enhanced.

  Further, according to the voltage detection device 1, the detection circuit 16 detects the detection voltage signal V2 in synchronization with the synchronization signal S2 and outputs the detection output V3, thereby detecting the detection output V3 with little influence of disturbance. Can be output.

  Further, according to the voltage detection device 1, the current / voltage conversion circuit 14 is configured to include the operational amplifier 14a and the feedback resistor 14b, so that the detection current I is detected with high sensitivity and converted into the detection voltage signal V2. Can.

  In the above example, a recess A is formed between one end of each of the magnets 21a and 21c on both sides, and the detection electrode 11 is disposed in the ultrasound excitation unit 13 in the recess A (above In the example, the configuration is adopted in which the insulator 25 is disposed on the end face of one end of the central magnet 21b), but as in the ultrasonic excitation unit 13A shown in FIG. A configuration in which the detection electrodes 11 are separated can also be employed. As an example, in the ultrasonic excitation unit 13A, as shown in the figure, the end face of one end of the magnet 21b is positioned in the imaginary plane W, and the hole formed at the center of the coil 23 Although a configuration for entering this one end of the magnet 21b (a configuration in which the coil 23 is formed on the outer periphery of this one end) is adopted, in the same manner as the ultrasonic excitation unit 13 described above, A configuration in which one end is recessed from the virtual plane W can also be employed. In addition, about the structure same as said ultrasonic excitation part 13, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  By adopting this configuration, as shown by reference numerals X and Y in FIG. 4, a position different from the application site of the static magnetic field M on the surface of the insulator 51 (a position X on the same side as the application site, position Y Can be arranged at the position opposite to the application site).

  Further, in the above-described ultrasonic excitation units 13 and 13A, a configuration is adopted in which the magnets 21 (magnets 21a, 21b, 21c) are arranged vertically on the surface of the application site of the detection target 52. As in the ultrasonic excitation unit 13B shown in FIG. 5, a configuration may be employed in which the magnet 21 is disposed in the horizontal state. In this configuration, although the strength of the static magnetic field M generated inside the application site in the detection target 52 is weaker than that of the above-described ultrasonic excitation units 13 and 13A, as shown in the figure, also in this configuration. It is possible to generate a static magnetic field M inside the application site along the surface of the application site. Therefore, also in the ultrasonic excitation unit 13B, the ultrasonic wave US can be generated along the depth direction of the detection target 52, so the detection target 52 is in the depth direction (a direction intersecting the surface of the application site. In the example, it can be oscillated along orthogonal directions).

DESCRIPTION OF SYMBOLS 1 Voltage detection apparatus 11 Detection electrode 13, 13A, 13B Ultrasonic excitation part 14 Current voltage conversion circuit 14a Operational amplifier 14b Feedback resistance 16 Detection circuit 21, 21a-21c Magnet 23 Coil 51 Insulator 52 Detection object
I Detection current Iac AC current Ied Eddy current
M Static magnetic field US Ultrasonic wave V1 voltage (voltage to be detected)
V2 detection voltage signal V3 detection output Vdi potential difference

Claims (5)

A voltage detection device for detecting a detection target voltage generated in a detection target covered with an insulator, comprising:
A detection electrode disposed in direct contact with the insulator directly or in a state where another insulator is interposed,
While applying a static magnetic field to the detection target, an eddy current is generated at the application site of the static magnetic field in the detection target to excite an ultrasonic wave vibrating in a direction crossing the surface of the application site to the detection target An ultrasonic excitation unit to
In a state in which the ultrasonic wave is excited in the detection target, the current flows from the detection target to the reference voltage via the detection electrode, and the amplitude is modulated according to the potential difference between the detection target voltage and the reference voltage A current-voltage conversion circuit that converts a detected current synchronized with the ultrasonic wave into a detected voltage signal;
And a detection circuit for detecting a detection output indicating the potential difference from the detection voltage signal.   The ultrasonic excitation unit generates a static magnetic field and applies the static magnetic field to the detection target, thereby generating a static magnetic field along the surface inside the application site of the detection target, and an alternating current supplied The voltage detection apparatus according to claim 1, further comprising: a coil for generating the eddy current on the basis of the detection target to excite the ultrasonic wave vibrating in a direction orthogonal to the surface of the application site.   In the magnet, the first magnet in which the coil is disposed in the vicinity of the magnetic pole on the application site side, and the magnetic poles on the respective application site side are magnetized in different polarities from the magnetic pole of the first magnet The voltage detection apparatus according to claim 2, further comprising: a second magnet and a third magnet disposed to sandwich the magnetic pole of the first magnet.   The voltage detection device according to any one of claims 1 to 3, wherein the detection circuit synchronously detects the detection voltage signal with a synchronization signal synchronized with the detection voltage signal to detect the detection output. The current voltage conversion circuit has a first input terminal defined by the reference voltage, a second input terminal connected to the detection electrode, and a feedback circuit between the second input terminal and the output terminal. The voltage detection device according to any one of claims 1 to 4, further comprising an operational amplifier connected to convert the detection current flowing in the feedback circuit into the detection voltage signal .

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