JP2008261785A - Voltage measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce dispersion of a measured voltage in a feedback voltage. <P>SOLUTION: This device equipped with a variable capacity circuit 19 connected between a detection electrode 12 and a case 11 and constituted to be able to change its capacitance C1, a voltage generation circuit 25 for generating an electric potential (feedback voltage V4 (hereafter referred to as the voltage V4)) of the case 11, and a voltage control part CNT for changing the voltage V4 relative to the voltage generation circuit 25, is constituted to be able to measure the voltage V1 of a measuring object 4. The variable capacity circuit 19 is equipped with a capacity change function body 13 wherein four constitutional units 31-34 including respectively the first electrical element constituted by connecting diodes reversely in series are connected circularly, and a connection point A is connected to the detection electrode 12, and a connection point C is connected to the voltage V4; a driving circuit 14 for applying a driving signal S2 to the interval between connection points B, D, and thereby changing the capacitance C1 of the capacity change function body 13; and a variable resistance circuit 36 for changing the ratio between a resistance component between connection points B, C and a resistance component between connection points C, D. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a voltage measuring apparatus that can measure the voltage of a measurement object.

  As this type of voltage measuring apparatus, a voltage measuring apparatus disclosed in Japanese Patent Laid-Open No. 4-305171 is known.

This voltage measuring device is a voltage measuring device (distance-compensated electrometer) used for measuring the charge density on both surfaces of a measurement object (charged body) in the prior art disclosed in Japanese Patent Laid-Open No. 4-305171. The probe unit includes a detection electrode and a vibrating body, an oscillator, a preamplifier, an amplifier, a synchronous detector, an integrator, a high voltage generator, and an impedance matching circuit. In this voltage measurement device, the detection electrode is opposed to the measurement object while being vibrated by the vibration body. At this time, the capacitance formed between the detection electrode and the measurement object changes, and the electric field strength between the measurement object and the detection electrode also changes. An AC voltage corresponding to the electric field strength between the detection electrode and the detection electrode is generated. The high voltage generator generates a DC voltage corresponding to the AC voltage and feeds it back to the voltage of the probe unit. In this case, the electric field strength between the measurement object and the detection electrode becomes zero when the voltage of the probe unit and the voltage of the charged body coincide. Therefore, when the electric field strength between the measurement object and the detection electrode becomes zero, that is, when the AC voltage generated at the detection electrode becomes zero volts, the high voltage generator feeds back to the probe unit. By detecting the DC voltage, the voltage of the measurement object is measured.
Japanese Patent Laid-Open No. 4-305171 (page 2, FIG. 6)

  However, each of the voltage measuring devices has the following problems. That is, in the voltage measuring device disclosed in Japanese Patent Laid-Open No. 4-305171, the detection electrode is vibrated by the vibrating body. Therefore, both voltage measuring devices have a problem that it is difficult to increase the operating frequency and it is difficult to improve the reliability due to the mechanically movable configuration. is doing.

  In order to solve this problem, the inventor of the present application has developed a variable capacitance circuit 19 (see FIG. 12) including capacitance change function bodies 13 and 13A to 13F as shown in FIGS. Yes. The capacitance change function bodies 13 and 13A to 13F (hereinafter also referred to as “capacitance change function body 13” unless otherwise specified) have first electric elements E11 to E14 configured by connecting diodes in series in opposite directions. (Hereinafter, when not particularly distinguished, it is also referred to as “first electric element E1”.) When an AC voltage (sinusoidal voltage) is applied to the first electric element E1, the capacitance C1 of the first electric element E1 becomes the AC voltage. Therefore, the mechanically movable configuration can be eliminated, and the operating frequency can be increased.

  Further, as shown in FIGS. 2 and 4 to 10, the capacity change function body 13 includes a first structural unit 31 (31 A), a second structural unit 32 (32 A), and a third structural unit 33 (33 A). , 33B) and the fourth structural unit 34 (34A) are annularly connected in this order to form a bridge circuit. In addition, as shown in FIG. 12, the capacitance changing function body 13 has a connection point A between the first structural unit 31 (31A) and the fourth structural unit 34 (34A) facing the detection electrode 12 (measurement object 4). The connection point C of the second structural unit 32 (32A) and the third structural unit 33 (33A, 33B) is connected via the current detector 15 to the reference potential (case). 11 potential). Further, in this variable capacitance circuit 19, a drive signal (sine wave signal) generated in the secondary winding 14c due to the drive signal S1 (sine wave signal) input to the primary winding 14b of the transformer 14a in the drive circuit 14. ) S2 is applied between the connection point B of the first structural unit 31 (31A) and the second structural unit 32 (32A) and the connection point D of the third structural unit and the fourth structural unit. However, the product of the impedances between the connection points A and B and between the connection points C and D and the product of the impedances between the connection points B and C and between the connection points D and A are set to be the same or substantially the same. Thus, the capacity changing function body 13 is configured so as to satisfy the equilibrium condition as a bridge circuit in design. As an example, in the capacitance change function body 13 shown in FIG. 2, the product of the impedances of the first structural unit 31 and the third structural unit 33, and the impedances of the second structural unit 32 and the fourth structural unit 34. The capacitance changing function body 13 is designed to satisfy the equilibrium condition as a bridge circuit by design.

  Therefore, in this variable capacitance circuit 19, the current i flowing through the capacitance change function body 13 or the voltage across the capacitance change function body 13 (voltage between the connection points A and C) theoretically has the frequency of the drive signal S1. Only twice the frequency component (the frequency component of the capacitance change of the capacitance change function body 13) is included, and the amplitude of the double frequency component is the voltage V1 of the measurement object 4 and the reference potential (the potential of the case 11, that is, the potential of the case 11). It is proportional to the potential difference with the feedback voltage V4). For this reason, the voltage V2 generated in the current detector 15 due to the current i is converted to the detection signal S3 by the preamplifier 16 and output, and the feedback voltage V4 (reference potential) so that the amplitude of the detection signal S3 decreases. By controlling this, it is possible to measure the voltage V1 of the measuring object 4 while omitting the process of separating the frequency component of the drive signal S1.

  However, in electronic parts such as diodes, there is generally some variation in electrical characteristics (for example, characteristics related to resistance components such as on-resistance and AC loss) between parts with the same electrical specifications. It is. For this reason, since it is difficult to configure the capacitance changing function body 13 so as to completely satisfy the equilibrium condition as a bridge circuit, the reference potential (feedback voltage V4) matches the voltage V1 of the measurement object 4. Even in such a case, the current i flowing through the capacitance change function body 13 or the voltage across the capacitance change function body 13 includes a frequency component twice the drive signal S2 and a frequency component of the drive signal S2. As a result, also in the detection signal S3, as shown in FIG. 13, the frequency component twice as high as the drive signal S2 (in the figure, the component whose frequency is 4.5 MHz as an example) and the frequency component of the drive signal S2 (same as the same) In the figure, as an example, a component having a frequency of 2.25 MHz is included. As a result, when the reference potential (feedback voltage V4) matches the voltage V1 of the measurement object 4, the current i that flows through the capacitance changing function body 13 whose amplitude should theoretically become zero, the voltage across the capacitance changing function body 13 In addition, the amplitude of the detection signal S3 may be increased as a result of combining the frequency component of the drive signal S2 and the frequency component twice the drive signal S2. For this reason, the subject that the dispersion | variation which arises in the feedback voltage V4 as a measurement result which shows the voltage V1 of the measuring object 4 becomes large exists.

  The present invention has been made to solve the above-described problems, and has as its main object to provide a voltage measuring apparatus that can reduce variations in voltage measurement.

  In order to achieve the above object, the voltage measuring device according to claim 1 is configured to be capable of changing its capacitance by being connected between a detection electrode capable of facing a measurement object and the detection electrode and a reference potential. A variable capacitance circuit, a voltage generation circuit that generates the reference potential, and a voltage control unit that changes the voltage of the reference potential relative to the voltage generation circuit when the variable capacitance circuit changes the capacitance. A voltage measuring device configured to measure the voltage of the measurement object, wherein the variable capacitance circuit functions as a resistor when one end is at a higher potential than the other end, and the one end is A first configuration unit and a second configuration each including a first electrical element formed by connecting two first elements functioning as a capacitor body in a reverse direction in series with each other at a low potential with respect to the other end Unit, third structural unit and fourth The structural units are configured to be annularly connected in this order, and the connection points of the first structural unit and the fourth structural unit are connected to the detection electrode, and the second structural unit and the third structural unit are connected. A capacitance change function body having a connection point of a structural unit connected to the reference potential; a connection point of the first structural unit and the second structural unit; a third structural unit; and a fourth structural unit. A drive circuit that changes an electrostatic capacity of the capacitance-changing function body by applying an AC voltage to a connection point; a connection point between the first structural unit and the second structural unit; and the second configuration The resistance component between the unit and the connection point of the third structural unit, and the connection point of the second structural unit and the third structural unit, the third structural unit, and the fourth structural unit. Change the ratio of resistance component to the connection point It is constituted by a variable resistor circuit.

  Further, the voltage measuring device according to claim 2 is a detection electrode that can be opposed to a measurement object, a variable capacitance circuit that is connected between the detection electrode and a reference potential, and is configured to change its capacitance. The voltage generation circuit that generates the reference potential, and the voltage control unit that changes the voltage of the reference potential with respect to the voltage generation circuit when the variable capacitance circuit changes the capacitance. A voltage measuring device configured to be able to measure a voltage of an object, wherein the variable capacitance circuit includes a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit in this order. The first structural unit and the fourth structural unit function as a resistor when one end is at a high potential relative to the other end, and the one end is connected to the other end. Function as a capacitor at low potential A second electrical unit that includes two first elements that are connected in series in opposite directions and that allows the second structural unit and the third structural unit to pass an AC signal. Each of the electrical components is included, and the connection points of the first structural unit and the fourth structural unit are connected to the detection electrode, and the connection points of the second structural unit and the third structural unit are Between the capacitance changing function body connected to the reference potential, the connection point of the first structural unit and the second structural unit, and the connection point of the third structural unit and the fourth structural unit. A drive circuit for applying an alternating voltage to change the capacitance of the capacitance change function body; a connection point between the first structural unit and the second structural unit; the second structural unit; and the third structural unit. Resistance component between the connection points of the structural units, And a variable resistance circuit that changes a ratio of resistance components between the connection points of the second structural unit and the third structural unit and the connection points of the third structural unit and the fourth structural unit. It is prepared for.

  The voltage measuring device according to claim 3 is a detection electrode that can be opposed to a measurement object, a variable capacitance circuit that is connected between the detection electrode and a reference potential, and is configured to change its capacitance. The voltage generation circuit that generates the reference potential, and the voltage control unit that changes the voltage of the reference potential with respect to the voltage generation circuit when the variable capacitance circuit changes the capacitance. A voltage measuring device configured to be able to measure a voltage of an object, wherein the variable capacitance circuit includes a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit in this order. The second structural unit and the third structural unit function as a resistor when one end is at a high potential relative to the other end, and the one end is connected to the other end. Function as a capacitor at low potential Each of the first electric elements configured by connecting the two first elements in series in opposite directions, and the first structural unit and the fourth structural unit prevent the passage of a DC signal while alternating current A third electrical element that allows passage of a signal, and a connection point of the first structural unit and the fourth structural unit is connected to the detection electrode, and the second structural unit and the second structural unit A capacitance change function body having a connection point of three structural units connected to the reference potential, a connection point of the first structural unit and the second structural unit, the third structural unit, and the fourth configuration A drive circuit that changes an electrostatic capacity of the capacitance change function body by applying an alternating voltage between the connection points of the units, the connection points of the first structural unit and the second structural unit, and the second Structural unit and the third structural unit A resistance component between the connection point, and a resistance component between the connection point of the second structural unit and the third structural unit and the connection point of the third structural unit and the fourth structural unit. And a variable resistance circuit for changing the ratio.

  The voltage measuring device according to claim 4 is a detection electrode that can be opposed to a measurement object, a variable capacitance circuit that is connected between the detection electrode and a reference potential, and is configured to change its capacitance. The voltage generation circuit that generates the reference potential, and the voltage control unit that changes the voltage of the reference potential with respect to the voltage generation circuit when the variable capacitance circuit changes the capacitance. A voltage measuring device configured to be able to measure a voltage of an object, wherein the variable capacitance circuit includes a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit in this order. One set of the first structural unit and the second structural unit, and the third structural unit and the fourth structural unit. Each structural unit has one end at a high potential relative to the other end. A first electric element configured by connecting two first elements that function as a resistor and that function as a capacitor when one end is at a low potential relative to the other end in series in opposite directions, respectively. Each of the other structural units includes a third electrical element that allows the passage of the AC signal while preventing the passage of the DC signal, and each of the first structural unit and the fourth structural unit. A capacitance changing function body in which a connection point is connected to the detection electrode and a connection point of the second structural unit and the third structural unit is connected to the reference potential, and the first structural unit and the first structural unit A drive circuit for applying an alternating voltage between a connection point of two structural units and a connection point of the third structural unit and the fourth structural unit to change a capacitance of the capacitance change function body; The first structural unit and the second structural unit A resistance component between the connection point of the unit and the connection point of the second structural unit and the third structural unit, and the connection point of the second structural unit and the third structural unit and the third structural unit And a variable resistance circuit that changes the ratio of the resistance component between the structural unit and the connection point of the fourth structural unit.

  The voltage measuring device according to claim 5 is the voltage measuring device according to any one of claims 1 to 4, wherein the first element is formed of a diode formed of a P-type semiconductor and an N-type semiconductor. Yes.

  The voltage measuring device according to claim 1, 2, 3 or 4, wherein the connection points of the first structural unit and the second structural unit and the connection points of the second structural unit and the third structural unit in the capacity change function body. And the ratio of the resistance component between the connection point of the second structural unit and the third structural unit and the connection point of the third structural unit and the fourth structural unit by the variable resistance circuit It can be changed. Therefore, according to these voltage measuring devices, since the balance adjustment of the resistance component of the capacitance change function body configured as a bridge circuit can be performed by operating the variable resistance circuit, it exists in an electronic component such as a diode. The first structural unit and the third structural unit (the third resistance unit in the variable resistance circuit) even in a situation where the equilibrium condition as the bridge circuit of the capacitance change function body is not satisfied due to the variation in the electrical characteristics. The product of each resistance component of the structural unit and the resistance component that is connected in parallel), the second structural unit (including the resistance component that is connected in parallel with the second structural unit in the variable resistance circuit), and the fourth configuration The product of each resistance component of the unit can be adjusted to be the same or substantially the same. As a result, according to these voltage measuring devices, the current flowing through the capacitance change function body when the reference potential converges to the voltage of the measurement object, and the AC voltage included in the voltage across the capacitance change function body. The frequency component can be reduced, and the amplitude of the current and the voltage between both ends can be reduced. Thereby, according to these voltage measuring devices, it is possible to reduce the variation in the reference potential as the measurement result indicating the voltage of the measurement object, and thus sufficiently improve the measurement accuracy of the voltage of the measurement object. Can do.

  In these voltage measuring devices, the variable capacitance circuit functions as a resistor when one end is at a high potential with respect to the other end, and as a capacitor when the one end is at a low potential with respect to the other end. The first electric element is formed by connecting two functioning first elements in series in opposite directions, and an electrostatic voltage of the variable capacitance circuit is applied by applying an AC voltage to the first electric element. A drive circuit for changing the capacitance is provided. Therefore, according to these voltage measuring devices, by configuring the variable capacitance circuit as the first element, for example, by a semiconductor element, the capacitance of the capacitance change function body is set to a period of one half of the period of the AC voltage ( As a result, the capacity can be changed at a high frequency of several hundred kHz to several MHz (the operating frequency (capacitance modulation frequency) can be increased). The voltage of the measurement object can be measured in a very short time. In addition, since the variable capacitance circuit has no mechanically movable portion, the reliability of the device can be improved.

  According to the voltage measuring device of the first aspect, the configuration of the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit can be made the same. The configuration can be simplified and the size can be greatly reduced.

  Further, according to the voltage measuring device of claim 2, 3 or 4, since the second electrical element or the third electrical element can be constituted by, for example, one capacitor, etc., the configuration using two first elements and In comparison, the number of parts can be reduced, and as a result, the product cost can be reduced. In addition, by using the resonator as the second electric element or the third electric element, the impedance of the structural unit formed of the resonator can be lowered at the capacity modulation frequency of the capacity change function body. A sufficient current can be passed through the capacity change function body. For this reason, the accuracy of voltage detection can be sufficiently increased.

  According to the voltage measuring device of the fifth aspect, since the first element is formed of a diode, the variable capacitance circuit, and thus the device itself can be configured easily and inexpensively.

  The best mode of a voltage measuring apparatus according to the present invention will be described below with reference to the accompanying drawings.

  First, a voltage measuring apparatus 1 according to the present invention will be described with reference to the drawings.

  As an example, the voltage measuring apparatus 1 includes a probe unit 2 and a main body unit 3 as shown in FIG. 1, and is configured to be able to measure the voltage V1 of the measuring object 4 in a non-contact manner. In this case, the voltage V1 refers to a voltage with respect to the ground potential (reference potential).

  As shown in FIG. 1, the probe unit 2 includes a case 11, a detection electrode 12, a variable capacitance circuit 19, a current detector 15, and a preamplifier 16. The case 11 is configured using a conductive material (for example, a metal material). For example, the detection electrode 12 is formed in a flat plate shape, and is fixed to the case 11 so that one surface side thereof is exposed on the outer surface of the case 11 and the other surface side is exposed inside the case 11. Yes. As an example, the detection electrode 12 is attached to a hole (not shown) provided in the case 11 in a state of closing the hole and being electrically insulated from the case 11. In this example, as an example, the case 11 has a surface covered with an insulating film formed of a resin material or the like. In this case, the detection electrode 12 may be covered with this insulating film, or may be exposed from the insulating film.

  As shown in FIG. 1, the variable capacitance circuit 19 includes one capacitance change function body 13, one drive circuit 14, and one variable resistance circuit 36. The variable capacitance circuit 19 (specifically, the capacitance changing function body 13) includes a first structural unit 31, a second structural unit 32, a third structural unit 33, and a fourth structural unit 34 in this order. It is configured as a so-called bridge circuit. Specifically, as shown in FIG. 2, each of the structural units 31, 32, 33, and 34 includes first electric elements E11, E12, E13, and E14 (hereinafter referred to as “first electric element E1 unless otherwise specified). Are also included one by one.

  In this case, each first electrical element E1 functions as a resistor when one end has a high potential with respect to the other end, and functions as a capacitor when the other end has a high potential with respect to the other end. Each of the first elements 41a and 41b (hereinafter also referred to as the first element 41 unless otherwise distinguished), and the first elements 41 are connected in series in opposite directions. Thereby, each 1st electric element E1 is comprised so that a capacity | capacitance may change according to the magnitude | size of the absolute value of an applied voltage, preventing passage of a DC signal. In this specification, “blocking the direct current signal” refers to the case where the direct passage of the direct current signal is completely blocked and the case where the direct current signal is restricted with a resistance value of, for example, 100 MΩ or more. It is a concept that includes. In this example, as an example, each first element 41 includes a P-type semiconductor and an N-type semiconductor that are joined to each other. Specifically, one first diode (for example, a variable-capacitance diode; a varicap or a varactor). Each first electric element E1 is configured by connecting these two diodes in series in opposite directions (with anode terminals connected to each other). In addition, variable capacitance diodes having the same or substantially the same characteristics are used for the first elements 41a and 41b, and the product of the impedances of the first structural unit 31 and the third structural unit 33 and the second configuration. The product of each impedance of the unit 32 and the fourth structural unit 34 is set so as to be the same or substantially the same in design (a state that is different within a range of several percent as an example).

  In the capacitance change function body 13 shown in FIG. 2, each first electrical element E1 connects one ends of the pair of first elements 41a and 41b (connects the anode terminals of the pair of diodes). Although configured, the first electric elements E1 can be configured by connecting the other ends of the pair of first elements 41a and 41b (connecting the cathode terminals of the pair of diodes). The variable capacitance diode uses a change in capacitance (junction capacitance) due to a change in the thickness of the depletion layer at the PN junction of the diode when a voltage is applied in the reverse direction. This is the one with a large change. On the other hand, even in a general diode (silicon diode) configured with a PN junction, the above-described change in capacitance (junction capacitance) occurs although it is less than a variable capacitance diode. Therefore, even if all the first elements 41a and 41b in each capacitance change function body 13 shown in FIG. 2 are replaced with the first elements constituted by general diodes, the capacitance change function body 13 is not changed. Can be configured.

  In addition, the variable capacitance circuit 19 is connected to the first structural unit 31 and the fourth structural unit 34 in the capacitance change function body 13 between the detection electrode 12 and a portion (case 11 in this example) that serves as a reference potential. The point A is disposed on the detection electrode 12 side, and the connection point C of the second structural unit 32 and the third structural unit 33 is disposed on the case 11 side. Specifically, as shown in FIG. 1, the variable capacitance circuit 19 has a connection point A of the capacitance change function body 13 connected to the detection electrode 12 and a connection point C of the capacitance change function body 13 connected to the current detector. 15 is connected to the case 11. A connection point B between the first structural unit 31 and the second structural unit 32 and a connection point D between the third structural unit 33 and the fourth structural unit 34 are connected to the drive circuit 14. The variable capacitance circuit 19 is disposed inside the case 11 without being exposed to the outside of the case 11.

  The drive circuit 14 is configured using, for example, insulating electronic components such as a transformer and a photocoupler, and drives the drive signal S1 (a signal having a high frequency such as several hundred kHz to several MHz) input from the main unit 3. It is electrically insulated from the signal S1 and converted into a drive signal S2 (AC voltage in the present invention) having the same frequency f1 as that of the drive signal S1 and output (applied) to the capacitance changing function body 13. In this example, as an example, the drive circuit 14 includes a transformer 14a in which each end of the secondary winding 14c is connected to the connection points B and D of the capacitance change function body 13 as shown in FIG. Based on the drive signal S1, the primary winding 14b of the transformer 14a is excited to generate the drive signal S2 in the secondary winding 14c. Instead of the drive circuit 14, a floating signal source (not shown) that outputs the drive signal S2 alone (without receiving the drive signal S1 from the main unit 3) is provided in the probe unit 2. You can also.

  As shown in FIG. 1, the variable resistance circuit 36 includes, as an example, a resistor (fixed resistor) 36a, a variable resistor 36b, and a resistor (fixed resistor) 36c, and these three resistors 36a, 36b, and 36c are serially connected in this order. Are connected to each other and function as one variable resistor as a whole. In the variable resistance circuit 36, one terminal (in this example, one terminal of the resistor 36a, which is a non-connection terminal to the variable resistor 36b) is connected to the first structural unit 31 and the second structural unit 32. The other terminal as a variable resistor is connected to the point B (in this example, one terminal is the other terminal of the resistor 36c connected to the variable resistor 36b and is not connected to the variable resistor 36b). The second structural unit 32 and the third structural unit are connected to the connection point D of the third structural unit 33 and the fourth structural unit 34, and the movable terminal (movable terminal of the variable resistor 36b) as a variable resistor is further connected. It is connected to 33 connection points C. With this configuration, the variable resistance circuit 36 has a resistance between the connection point B of the first structural unit 31 and the second structural unit 32 and the connection point C of the second structural unit 32 and the third structural unit 33. Component (resistance value) and a resistance component (resistance) between the connection point C of the second structural unit 32 and the third structural unit 33 and the connection point D of the third structural unit 33 and the fourth structural unit 34 Value) ratio can be changed.

  Each resistor 36a, 36c is a fixed resistor having a resistance value of several kΩ to several tens of kΩ (in this example, a fixed resistor of 4 kΩ), and the variable resistor 36b has a resistance value of several hundred Ω to several kΩ. Variable resistance (in this example, a variable resistance of 500Ω as an example) is used. In this example, in order to limit the range of the balance adjustment for the capacitance changing function body 13 by the variable resistor 36b, the resistors 36a and 36c are disposed on both sides of the variable resistor 36b, and the resistance values of the resistors 36a and 36c are set. Although defined to be the same, depending on the range to be limited, the ratio of the resistance value of the variable resistor 36b to the resistance value of each resistor 36a, 36c may be changed, or the resistance value of the resistors 36a, 36c may be different. Also, the arrangement of one or both of the resistors 36a and 36c may be omitted.

  The current detector 15 is configured by a resistor as an example, and is connected between the variable capacitance circuit 19 (specifically, the capacitance changing function body 13 of the variable capacitance circuit 19) and the case 11. Thus, the current detector 15 is disposed between the detection electrode 12 and the case 11 while being connected in series with the variable capacitance circuit 19, and flows into the capacitance changing function body 13 of the variable capacitance circuit 19. While detecting the current i, a voltage V2 having a value proportional to the current value of the current i and having a polarity corresponding to the direction of the current i is generated between both ends thereof. The preamplifier 16 includes a pair of DC blocking capacitors (not shown), an amplifier circuit (not shown) (not shown), and insulating electronic parts (not shown) (transformers and photocouplers). Further, in this example, the preamplifier 16 is configured by a differential operational amplifier as an example, and amplifies the voltage V2 input through the capacitor by an amplifier circuit, and the amplified voltage is amplified by an insulating electronic component. Is converted into a detection signal S3 that is electrically insulated and output. In this case, since the voltage V2 changes in proportion to the value of the current i, the detection signal S3 generated by amplifying the voltage V2 also changes in proportion to the value of the current i. Further, the current detector 15 and the preamplifier 16 described above are disposed inside the case 11 together with the variable capacitance circuit 19.

  As shown in FIG. 1, the main unit 3 includes an oscillation circuit 21, an A / D conversion circuit 22, a CPU 23, a D / A conversion circuit 24, a voltage generation circuit 25, and a voltmeter 26. In this case, the oscillation circuit 21 generates a drive signal S1 having a constant period T1 (frequency f1, in this example, 2.25 MHz as an example) and outputs the drive signal S1 to the probe unit 2. In this example, the oscillation circuit 21 generates a sine wave signal as the drive signal S1. The A / D conversion circuit 22, together with the CPU 23 and the D / A conversion circuit 24, constitutes a voltage control unit CNT in the present invention, converts the detection signal S3 as an analog signal into digital data D1, and outputs it to the CPU 23.

  The CPU 23 extracts from the input digital data D1 a detection process (filtering process) for extracting data on a component in a predetermined frequency band including, for example, a frequency f2 that is twice the frequency f1 of the drive signal S1, and this detection process. Integration processing for integrating the acquired data. Further, the CPU 23 outputs the integration data D2 obtained by this integration processing to the D / A conversion circuit 24.

  The D / A conversion circuit 24 converts the integration data D2 into a DC voltage V3 as an analog signal and outputs it to the voltage generation circuit 25. The voltage generation circuit 25 generates a feedback voltage V4 and applies it to the case 11 of the probe unit 2 under the control of the voltage control unit CNT. Specifically, the voltage generation circuit 25 generates the feedback voltage V4 by amplifying the input DC voltage V3. Thereby, the voltage of case 11 which is a reference potential is maintained equal to the feedback voltage V4. The voltmeter 26 measures the feedback voltage V4 with reference to the reference potential (the potential of the connection terminal CP, the ground potential), and displays the voltage value. The voltmeter 26 may adopt a configuration in which the measured voltage value of the feedback voltage V4 is converted into digital data and output to the outside.

  Next, the measuring operation of the voltage measuring device 1 will be described together with the measuring method of the voltage V1 of the measuring object 4 using the voltage measuring device 1.

  First, the voltage measuring device 1 is calibrated before measuring the voltage V1. Specifically, first, the detection electrode 12 is opposed to a reference object (not shown) having a constant voltage in a non-contact state, and then the voltage measuring device 1 is activated. In the voltage measurement device 1, in a startup state, as described later, in a feedback loop composed of a current detector 15, a preamplifier 16, an A / D conversion circuit 22, a CPU 23, a D / A conversion circuit 24, and a voltage generation circuit 25. Negative feedback is performed so that the potential difference between the measurement object 4 and the case 11 gradually decreases (decreases). As a result, when a predetermined time has elapsed from the start-up, the feedback voltage V4 matches the voltage of the reference object. In this state, the voltage measuring device 1 is calibrated by operating the movable terminal of the variable resistor 36b of the variable resistor circuit 36 while observing the waveform of the detection signal S3 output from the probe unit 2 with an oscilloscope or the like. This is done by adjusting so that the amplitude of S3 is minimized.

  This calibration will be described in detail. As described above, the capacitance changing function body 13 is included in each of the structural units 31 to 34 although it is configured in design so as to satisfy the equilibrium condition as a bridge circuit. Even if the feedback voltage V4 coincides with the voltage of the reference object due to variations in characteristics of components such as diodes, the current i flowing through the capacitance change function body 13 and between both ends of the capacitance change function body 13 As a result of the voltage (voltage between connection points A and C) including the frequency component twice the drive signal S2 and the frequency component of the drive signal S2, the amplitude of the detection signal S3 may increase as shown in FIG. . However, in this voltage measuring apparatus 1, even in such a case, by operating the variable resistor 36 b of the variable resistor circuit 36, the resistance component (resistance value) between the connection points B and C of the capacitance changing function body 13, In addition, the ratio of the resistance component (resistance value) between the connection points C and D can be changed, whereby the balance adjustment of the resistance component of the capacitance change function body 13 configured as a bridge circuit can be performed. In other words, due to variations in electrical characteristics (characteristics regarding the resistance component) existing in electronic components such as diodes, the equilibrium condition (equilibrium condition regarding the resistance component) as the bridge circuit of the capacitance change function body 13 is satisfied. Even in such a situation, by changing the ratio of the resistance component between the connection points B and C of the capacitance changing function body 13 and the resistance component between the connection points C and D, the connection between the connection points A and B and the connection point C, The product of each resistance component (resistance value) between D and the product of each resistance component (resistance value) between the connection points B and C and between the connection points D and A can be adjusted to be the same or substantially the same. Therefore, as shown in FIG. 11, when the equilibrium condition for the resistance component of the two types of frequency components described above breaks down, the current i and the voltage across the capacitance change function body 13 (between the connection points A and C). The frequency component of the drive signal S2 generated in the voltage) can be reduced, and the amplitude of the entire detection signal S3 can also be reduced (about 30 to 40% in FIG. 11 with respect to the amplitude shown in FIG. 13). Reduced).

  After this calibration is completed, the probe unit 2 is disposed in the vicinity of the measurement object 4 so that the detection electrode 12 faces the measurement object 4 in a non-contact state for measuring the voltage V1. As a result, as shown in FIG. 1, the capacitance C <b> 0 is formed between the detection electrode 12 and the measurement object 4. In this case, the capacitance value of the capacitance C0 varies in inverse proportion to the distance between the detection electrode 12 and the measurement object 4, but after the probe unit 2 is completely disposed, the environmental conditions such as humidity are constant. Originally constant (does not change). However, the capacitance C0 varies when environmental conditions such as humidity change.

  In the voltage measurement device 1 in the activated state, in the main unit 3, the oscillation circuit 21 starts generating the drive signal S 1 and outputs the drive signal S 1 to the probe unit 2. In the probe unit 2, the drive circuit 14 of the variable capacitance circuit 19 converts the input drive signal S <b> 1 into the drive signal S <b> 2 and applies (outputs) between the connection points B and D of the capacitance change function body 13. At this time, in the capacity change function body 13, the drive signal S2 applied between the connection points B and D is divided, and the first structural unit 31, the second structural unit 32, and the third structural unit are divided. 33 and the fourth structural unit 34, respectively.

  In this case, as shown in FIG. 3, the potential at the connection point B becomes high with respect to the period Ta (the connection point D as a reference) in one cycle T1 of the drive signal S2, and the potential difference between them gradually increases. In the period), the reverse voltage in each first electrical element E1 is applied (reversely biased), and each capacitance of each first element 41 functioning as a capacitor gradually decreases. Specifically, the capacitance of each first element 41b that is reverse-biased in each of the first electric elements E11 and E14, and each of the first electric elements E12 and E13 that are reverse-biased. The capacitance of the first element 41a gradually decreases. Further, during the period Tb of one cycle T1 of the drive signal S2 (period in which the potential at the connection point B becomes high with the connection point D as a reference and the potential difference between the two gradually decreases), the drive signal S2 is reverse-biased. Each of the first elements 41, specifically, each of the first electric elements E11 and E14 has a capacitance of each first element 41b, and each of the first electric elements E12 and E13 has a capacitance of each of the first elements 41a gradually. To increase.

  Further, during the period Tc of one cycle T1 of the drive signal S2 (period in which the potential at the connection point B is low with respect to the connection point D and the potential difference between the two gradually increases), the drive signal S2 is reverse-biased. Each first element 41 that functions as a capacitor, specifically, each first element 41a in each first electrical element E11, E14, and each electrostatic element in each first element 41b in each first electrical element E12, E13. Capacity gradually decreases. Further, during the period Td of one cycle T1 of the drive signal S2 (a period in which the potential at the connection point B is low with respect to the connection point D and the potential difference between the two gradually decreases), the drive signal S2 is reverse-biased. Each first element 41a, specifically each first element 41a in each first electric element E11, E14, and each first element 41b in each first electric element E12, E13 is gradually increased in capacitance. To increase. Note that the first elements 41a and 41b to which the forward voltage is applied (forward biased) among the first elements 41a and 41b included in each first electrical element E1 function equivalently as resistors. is doing. For this reason, the capacitance of each first electrical element E1 repeats decreasing and increasing twice within one cycle T1 of the drive signal S2.

  Thus, since the capacitance of each first electrical element E1 included in each structural unit 31 to 34 repeats increasing and decreasing twice each in one cycle T1 of the drive signal S2, these The capacitance C1 (capacitance between the connection points A and B) of the capacitance changing function body 13 formed by synthesizing the capacitance is repeatedly increased and decreased twice. In other words, the variable capacitance circuit 19 continuously increases the capacitance C1 in synchronization with the cycle T1 of the input drive signal S2 and at a cycle T2 (frequency f2 = 2 × f1) that is a half of the cycle T1. In the example, an operation that changes periodically is executed. In this case, as described above, since the variable capacitance circuit 19 is connected in series between the case 11 and the detection electrode 12 with the current detector 15 interposed, the capacitance C1 and the measurement object The capacitance C0 formed between the body 4 and the detection electrode 12 is in a state of being connected in series between the measurement target body 4 and the case 11. For this reason, when the electrostatic capacitance C1 periodically changes at the frequency f2 (capacitance modulation frequency), the electrostatic capacitance C2 between the measurement object 4 and the case 11 (the series combination of the electrostatic capacitances C0 and C1). As shown in FIG. 3, the (capacitance) also changes in synchronization with the cycle T1 of the drive signal S2 and in a cycle T2 (frequency f2) which is a half of the cycle T1.

  Further, in the variable capacitance circuit 19, each set connected to the connection point C and each set of the first electrical elements E 11 and E 14 included in each of the structural units 31 and 34 connected to the connection point A. Since the two first electric elements E1 included in at least one of the groups of the first electric elements E12 and E13 included in the units 32 and 33 both function as capacitors at all times. Although the detection electrode 12 and the case 11 are connected in an AC manner via the variable capacitance circuit 19, they are maintained in a state where they are not short-circuited in terms of DC.

  In addition, immediately after the operation of the voltage measuring apparatus 1 is started, the integration process by the CPU 23 of the main body unit 3 is also started, so that the integration data D2 output from the CPU 23 is almost zero. The DC voltage V3 output from the conversion circuit 24 is also almost zero. Therefore, the voltage generation circuit 25 generates a feedback voltage V4 of approximately zero volts and applies it to the case 11 of the probe unit 2. For this reason, a potential difference (V1−V4) is generated between the case 11 of the probe unit 2 and the measurement object 4 in the voltage measuring apparatus 1.

  Therefore, as described above, in the probe unit 2 of the voltage measuring device 1, the potential difference (V1−V4) between the measurement object 4 and the case 11 is based on the periodic change of the capacitance C1 in the cycle T2. ) Current i (cycle T2) having an amplitude corresponding to In this case, the amplitude (current value) of the current i flowing through the capacitance change function body 13 increases when the potential difference (V1-V4) is large, and the current value decreases when the potential difference (V1-V4) is small. That is, although not shown, the current i flowing through the capacitance changing function body 13 flows as an AC signal whose period is T2 and whose amplitude changes according to the potential difference (V1-V4). The preamplifier 16 amplifies the voltage V2 generated at both ends of the current detector 15 due to the current i, and outputs it to the main unit 3 as a detection signal S3. In this case, the detection signal S3 mainly includes the same frequency component as the frequency f2 of the current i, and also includes the same frequency component as the frequency f1 of the drive signal S2.

  In the voltage control unit CNT of the main unit 3, the A / D conversion circuit 22 converts the detection signal S 3 into digital data D 1 and outputs it to the CPU 23. The CPU 23 performs a detection process on the input digital data D1 to extract data about a component in a predetermined frequency band including the frequency f2, and further executes an integration process to integrate the extracted data. Integration data D2 is generated and output. The D / A conversion circuit 24 converts the integration data D2 into a DC voltage V3 as an analog signal and outputs it to the voltage generation circuit 25. The voltage generation circuit 25 amplifies the DC voltage V3 to generate a feedback voltage V4. Then, it is applied to the case 11 of the probe unit 2. The voltmeter 26 displays the voltage value of the feedback voltage V4. In this way, in the feedback loop including the current detector 15, the preamplifier 16, the A / D conversion circuit 22, the CPU 23, the D / A conversion circuit 24, and the voltage generation circuit 25, each component operates as described above. As a result, the feedback voltage V4 rapidly converges to the voltage V1 of the measurement object 4, the potential difference (V1-V4) becomes almost zero in a short time, and the current i flowing through the capacitance changing function body 13 of the probe unit 2 is also Nearly zero.

  Further, once the feedback voltage V4 converges to the voltage V1 of the measurement object 4, the components constituting the feedback loop operate as described above, thereby following the fluctuation of the voltage V1 of the measurement object 4. To do. Accordingly, the voltage V1 is continuously displayed on the voltmeter 26 in accordance with the change in the voltage V1 of the measurement object 4. At this time, since the amplitude of the entire detection signal S3 output from the probe unit 2 is reduced by the calibration described above, the voltage V1 is displayed on the voltmeter 26 with little variation.

  As described above, in the voltage measuring device 1, the variable resistance circuit 36 can change the resistance component between the connection points B and C and the ratio of the resistance component between the connection points C and D in the capacitance changing function body 13. Yes. Therefore, according to the voltage measuring apparatus 1, since the balance adjustment of the resistance component of the capacitance change function body 13 configured as a bridge circuit can be performed by operating the variable resistance circuit 36, an electronic component such as a diode is provided. The first structural unit 31 and the third structural unit 33 (variable resistor 33) even in a situation where the balance condition as the bridge circuit of the capacitance change function body 13 is not satisfied due to variations in the electrical characteristics existing in The product of each resistance component of the circuit 36 including the resistance component that is in parallel connection with the third structural unit 33 and the second structural unit 32 (in parallel connection with the second structural unit 32 in the variable resistance circuit 36). The product of each resistance component of the fourth structural unit 34 can be adjusted to be the same or substantially the same. As a result, when the feedback voltage V4 converges to the voltage V1 of the measurement object 4 (the feedback voltage V4 is the voltage V1 of the measurement object 4), the current i flowing through the capacitance change function body 13 and the capacitance change function body The frequency component of the drive signal S2 included in the voltage across both ends 13 can be reduced, and the amplitude of the current i and the voltage across the ends can be reduced. Thereby, according to this voltage measuring apparatus 1, since the dispersion | variation which arises in the feedback voltage V4 as a measurement result which shows the voltage V1 of the measuring object 4 can be reduced, the measurement accuracy of the voltage V1 of the measuring object 4 is improved. It can be improved sufficiently.

  The voltage measuring apparatus 1 also functions as a resistor when one end has a high potential with respect to the other end, and functions as a capacitor when the other end has a high potential with respect to the other end. A variable capacitance circuit 19 is configured including first electrical elements E11, E12, E13, and E14 configured by connecting elements 41a and 41b in series in opposite directions, and the drive circuit 14 includes first electrical elements E11 to E14. The capacitance C1 of the variable capacitance circuit 19 is changed by applying the drive signal S2 to the variable capacitance circuit 19. Therefore, according to the voltage measuring apparatus 1, the variable capacitance circuit 19 is configured by semiconductor elements (diodes in this example) as the first elements 41a and 41b, thereby driving the capacitance C1 of the capacitance changing function body 13. Capacitance change operation at a high frequency such as several hundred kHz to several MHz is possible (can be performed at a high frequency of several hundred kHz to several MHz). As a result, the voltage V1 of the measurement object 4 can be measured in a very short time. Moreover, according to the voltage measuring apparatus 1, since the variable capacitance circuit 19 has no mechanically movable part, the reliability of the apparatus can be improved.

  Furthermore, in the voltage measuring apparatus 1, the first structural unit 31, the second structural unit 32, the third structural unit 33, and the fourth structural unit 34 are all configured to include the first electrical element E1. Yes. Therefore, according to the voltage measuring apparatus 1, the configuration of the first structural unit 31, the second structural unit 32, the third structural unit 33, and the fourth structural unit 34 can be made the same. The configuration of 13 can be simplified and the size can be greatly reduced. In addition, by using diodes as the first elements 41a and 41b, the variable capacitance circuit 19, and thus the voltage measuring device 1, can be configured easily and inexpensively.

  In addition, this invention is not limited to said structure. For example, in the capacitance change function body 13 of the variable capacitance circuit 19 described above, as shown in FIG. 2, all the structural units 31 to 34 are configured so as to include the first electrical element E1, respectively. In the capacity change function body 13 shown in the figure, the second structural unit 32 and the third structural unit 33 included in the first to fourth structural units 31 to 34 are included. One electric element can be replaced with a second electric element that allows passage of an AC signal, and the capacitance changing function body can be configured. In this case, the second electrical element includes at least one of a capacitor, a coil, a resistor, and a resonator. As an example, the capacity change function body 13A shown in FIG. 4 uses the second electrical units E12 and E13 of the second structural unit 32 and the third structural unit 33 in the capacity change function body 13 shown in FIG. The second structural unit 32A and the third structural unit 33A are configured to be replaced by electrical elements E22 and E23 (capacitors 62 and 63 having the same electrical characteristics), respectively. Instead of the capacitors 62 and 63, a pair of coils 62a and 63a having the same electrical characteristic (inductance value) may be used, or a pair of resistors 62b and 63b having the same electrical characteristic (resistance value) may be used. Alternatively, a pair of resonators 62c and 63c having the same electrical characteristics (frequency-impedance characteristics) may be used. In this case, the resonators 62c and 63c have a minimum impedance at a frequency (capacitance modulation frequency) f2 that is twice the frequency f1 of the drive signal S2, and a sufficiently high impedance at other frequencies. Use a resonator with electrical characteristics. Specifically, various resonators such as a ceramic resonator, a crystal resonator, and an LC resonance circuit (series resonance circuit) including a coil and a capacitor can be used. Further, the resonators 62c and 63c may be configured to allow a direct current to pass therethrough.

  Also in the voltage measuring apparatus 1 provided with the capacitance change function body 13A, the variable resistance circuit 36 is provided, and the capacitance change is performed under the situation where the equilibrium condition (balance condition regarding the resistance component) as the bridge circuit is not satisfied. By changing the ratio of the resistance component between the connection points B and C of the functional body 13A and the resistance component between the connection points C and D, each resistance component between the connection points A and B and between the connection points C and D is changed. Since the product and the product of each resistance component between the connection points B and C and between the connection points D and A can be adjusted to be the same or substantially the same, the measurement object 4 is measured in the same manner as the capacitance changing function body 13. As a result of reducing the variation in the feedback voltage V4 as the measurement result indicating the voltage V1, the measurement accuracy of the voltage V1 of the measurement object 4 can be improved. In addition, since there is no mechanically movable configuration, a capacitance changing operation at a high frequency is possible, and a highly reliable variable capacitance circuit can be realized. Further, in the capacity change function body 13A, similarly to the capacity change function body 13, since at least a pair of adjacent structural units includes the first electrical element E1, the drive signal S2 is applied between the connection points B and D. When this is done, the capacitance C1 between the connection points A and C changes at a frequency f2 that is twice the frequency f1 of the drive signal S2. For this reason, the voltage measuring device 1 (see FIG. 1) using the capacitance changing function body 13A also sufficiently improves the reliability of the device itself in the same manner as the voltage measuring device 1 using the capacity changing function body 13. However, the feedback voltage V4 can be controlled at a high frequency such as several hundred kHz to several MHz (the operating frequency can be increased), so that the voltage V1 of the measurement object 4 can be measured in a short time. it can. Also in the capacity changing function body 13A, each of the structural units 31 and 34 connected to the connection point A includes the first electrical element (an electrical element that always functions as a capacitor). For this reason, although the detection electrode 12 and the case 11 are connected in an AC manner via the variable capacitance circuit 19, they can be maintained in a state where they are not short-circuited in terms of DC. Further, by using the resonators 62c and 63c having the electrical characteristics described above, the resonators 62c and 63c (that is, the resonators 62c and 63c) are formed at the capacitance modulation frequency (frequency f2) of the capacitance changing function body 13A. As a result, the impedance of each of the structural units 32A and 33A) can be lowered, so that a sufficient alternating current (current i) can be passed through the capacity change function body 13A. For this reason, the accuracy of voltage detection in the voltage measuring apparatus 1 using the capacity change function body 13A can be sufficiently increased.

  In the capacity change function body 13 shown in FIG. 2, the first electrical element included in the first structural unit 31 and the fourth structural unit 34 among the first to fourth structural units 31 to 34. The capacitance changing function body can be configured by replacing E1 with a third electrical element that allows passage of an AC signal while preventing passage of a DC signal. In this case, the third electrical element includes at least one of a capacitor and a resonator. As an example, the capacity change function body 13A-1 illustrated in FIG. 5 includes the first electrical elements E11 and E14 of the first structural unit 31 and the fourth structural unit 34 in the capacity change function body 13 illustrated in FIG. It is configured to include a first structural unit 31A and a fourth structural unit 34A that are respectively replaced by third electrical elements E31 and E34 (capacitors 61 and 64 having the same electrical characteristics as an example). Instead of the capacitors 61 and 64, a pair of resonators 61a and 64a having the same electrical characteristics (frequency-impedance characteristics) may be used. In this case, the resonators 61a and 64a have a minimum impedance at a frequency (capacitance modulation frequency) f2 that is twice the frequency f1 of the drive signal S2, and a sufficiently high impedance at other frequencies. Use a resonator with electrical characteristics. Specifically, various resonators such as a ceramic resonator, a crystal resonator, and an LC resonance circuit (series resonance circuit) including a coil and a capacitor can be used. The resonators 61a and 64a are configured to block the passage of direct current.

  In the capacity change function body 13 shown in FIG. 2, the set of the first structural unit 31 and the second structural unit 32 among the first to fourth structural units 31 to 34, and the third structural unit. The first electrical element E1 included in each of the structural units of one set of the group 33 and the fourth structural unit 34 is allowed to pass the AC signal while blocking the passage of the DC signal. The capacitance changing function body can be configured by replacing with three electrical elements. In this case, the third electrical element includes at least one of a capacitor and a resonator. As an example, the capacity change function body 13B shown in FIG. 6 uses a third structural unit 33 and a fourth structure unit 34 in the capacity change function body 13 shown in FIG. The third structural unit 33B and the fourth structural unit 34A are configured to be replaced by electrical elements E33 and E34 (capacitors 63 and 64 having the same electrical characteristics as an example). Instead of the capacitors 63 and 64, a pair of resonators 63d and 64a having the same electrical characteristics (frequency-impedance characteristics) may be used. In this case, the resonators 63d and 64a have a minimum impedance at a frequency (capacitance modulation frequency) f2 that is twice the frequency f1 of the drive signal S2, and a sufficiently high impedance at other frequencies. Use a resonator with electrical characteristics. Specifically, various resonators such as a ceramic resonator, a crystal resonator, and an LC resonance circuit (series resonance circuit) including a coil and a capacitor can be used. The resonators 63d and 64a are configured to block the passage of direct current.

  Also in the voltage measuring device 1 including the capacitance change function body 13A-1 or the capacitance change function body 13B, the variable resistance circuit 36 is provided so that the capacitance change function body 13A-1 or the capacity change function body 13B is a bridge circuit. As a result, the resistance component between the connection points B and C of the capacitance change function bodies 13A-1 and 13B and the resistance between the connection points C and D are not satisfied. By changing the ratio of the components, the product of each resistance component between the connection points A and B and between the connection points C and D, and the product of each resistance component between the connection points B and C and between the connection points D and A Can be adjusted to be the same or substantially the same. For this reason, in the same manner as the configuration including the capacitance changing function body 13, the variation occurring in the feedback voltage V4 as the measurement result indicating the voltage V1 of the measurement object 4 can be reduced. As a result, the measurement of the voltage V1 of the measurement object 4 Accuracy can be improved. In addition, since there is no mechanically movable configuration, a capacitance changing operation at a high frequency is possible, and a highly reliable variable capacitance circuit can be realized. Further, in the configuration using the capacity change function body 13A-1 or the capacity change function body 13B, as in the configuration using the capacity change function body 13, at least a pair of adjacent structural units is the first electrical element E1. Therefore, when the drive signal S2 is applied between the connection points B and D, the capacitance C1 between the connection points A and C changes at a frequency f2 that is twice the frequency f1 of the drive signal S2. . Therefore, the voltage measuring device 1 (see FIG. 1) using the capacitance changing function body 13A-1 or the capacity changing function body 13B is similar to the voltage measuring device 1 using the capacity changing function body 13, and the device itself. As a result, the feedback voltage V4 can be controlled at a high frequency such as several hundred kHz to several MHz (the operating frequency can be increased). Can be measured.

  Further, in the capacity change function body 13A-1 or the capacity change function body 13B, by using the resonators 61a, 63d, and 64a having the electrical characteristics described above, the capacity change function body 13A-1 or the capacity change function body 13B can be used. As a result, the impedance of each of the resonators 61a, 63d, and 64a (that is, the structural units 31A, 33B, and 34A configured by the resonators 61a, 63d, and 64a) can be reduced at the capacitance modulation frequency (frequency f2). A sufficient alternating current (current i) can be passed through the change function body 13A-1 or the capacity change function body 13B. For this reason, the accuracy of the voltage detection in the voltage measuring device 1 using the capacity change function body 13A-1 or the capacity change function body 13B can be sufficiently increased.

  In addition, in the capacitance changing function body 13A-1, each of the structural units 31A and 34A connected to the connection point A is a third electrical element (always functioning as a capacitor and prevents the passage of a DC signal). Electrical elements that allow the passage of AC signals). For this reason, in the voltage measuring apparatus 1 provided with this capacity change function body 13A-1, although the detection electrode 12 and the case 11 are connected in alternating current through the variable capacitance circuit 19, they are not short-circuited in direct current. Can be maintained in a state. In the capacity change function body 13B, one of the structural units 31 and 34A connected to the connection point A includes a first electrical element (an electrical element that always functions as a capacitor), and the other is a capacitor or One of the structural units 32 and 33 each including a resonator having a direct current passage blocking function and connected to the connection point C serves as a first electrical element (an electrical element that always functions as a capacitor). And the other includes a capacitor or a resonator having a function of preventing the passage of direct current. For this reason, although the detection electrode 12 and the case 11 are connected in an AC manner via the variable capacitance circuit 19, they can be maintained in a state where they are not short-circuited in terms of DC.

  The capacity change function bodies 13A, 13A-1, and 13B shown in FIGS. 4 to 6 are not limited to the above-described configuration, and are not illustrated. For example, the first electrical elements E11, E12, and E13 , E14 may be configured by a general diode (silicon diode) instead of the variable capacitance diode, or by a pair of diodes (variable capacitance diode or silicon diode) connected in series with the cathode terminals connected to each other. It can also be configured.

  Further, in the capacitance change function body 13 shown in FIG. 2, each of the structural units 31 to 34 is configured by a pair of first elements 41a and 41b (specifically, general variable capacitance diodes). The pair of variable capacitance diodes constituting the units 31 to 34 are connected in series in opposite directions by connecting the anode terminals to each other. That is, each of the structural units 31 to 34 is configured by arranging a P-type semiconductor and an N-type semiconductor in the form of N-P-P-N. Therefore, by replacing the pair of first elements 41a and 41b (diodes) constituting each of the structural units 31 to 34 with one NPN bipolar transistor TR1 to TR4 in the capacitance change function body 13 shown in FIG. Each of the first electric elements E1 included in the units 31 to 34 can be configured by one transistor to form the capacitance changing function body 13C shown in FIG. In this capacitance change function body 13C, each of the transistors TR1 to TR4 has its input terminal (one of the collector terminal and the emitter terminal) and its output terminal (the other of the collector terminal and the emitter terminal) connected to each other (respectively connected to the connection point). It is arranged in an annular path composed of the respective structural units 31 to 34. Note that the control terminals (base terminals) of the transistors TR1 to TR4 are not connected (does not become connection points).

  Further, in the capacity change function body 13 shown in FIG. 2, the structural units 31 and 34, the structural units 31 and 32, the structural units 32 and 33, and the structural units 33 and 33 are sandwiched between the connection points A, B, C, and D. One diode included in each of the first electric elements E1 of 34 is adjacent to each other (specifically, the diodes are connected in series in opposite directions to each other). In this way, the first electric element E1 is constituted by a pair of diodes connected in series in opposite directions, and the capacitance changing function body 13 in which at least two adjacent structural units include the first electric element E1. Then, one diode included in each first electrical element E1 is connected in series in opposite directions with a connection point between the two structural units interposed therebetween. For this reason, in this capacitance change function body 13, two P-type semiconductors and two N-type semiconductors constituting each diode are arranged in the order of PNNP via this connection point. . Specifically, in the capacitance change function body 13 of FIG. 2, a set of the first element 41 b of the fourth structural unit 34 and the first element 41 a of the first structural unit 31, and the first of the first structural unit 31. A set of one element 41b and the first element 41a of the second structural unit 32, a set of the first element 41b of the second structural unit 32 and the first element 41a of the third structural unit 33, and a third In the set of the first element 41b of the structural unit 33 and the first element 41a of the fourth structural unit 34, the two diodes constituting each of the first elements 41a and 41b are connected in series in opposite directions. Two P-type semiconductors and two N-type semiconductors are arranged in the order of P—N—N—P across the connection points A, B, C, D. Therefore, the capacitance changing function body 13D shown in FIG. 8 can be configured by replacing two diodes in each group with one PNP-type bipolar transistor TR5 to TR8. In this case, each first electrical element E1 is composed of a part of one transistor and a part of the other one transistor. In the capacitance change function body 13D, each of the transistors TR5 to TR8 has an input terminal (one of the collector terminal and the emitter terminal) and an output terminal (the other of the collector terminal and the emitter terminal) in the same manner as the capacitance change function body 13C. Are connected to each other (each as a connection point) and arranged in an annular path constituted by the respective structural units 31 to 34. On the other hand, the control terminals (base terminals) of the transistors TR5 to TR8 are used as connection points A, B, C, and D, unlike the capacitance change function body 13C.

  Further, each variable capacitance diode 13 in the capacitance change function body 13 shown in FIG. 2 is turned in the reverse direction, and each first electric unit of each of the structural units 31 to 34 is composed of a pair of diodes connected in series with the cathode terminals connected to each other. The capacity change function body (not shown) in which the target element E1 is configured can be replaced with PNP-type bipolar transistors TR5 to TR8 as in the capacity change function body 13E shown in FIG. It can be replaced by NPN bipolar transistors TR1 to TR4 as shown in the capacitance changing function body 13F shown. In this way, by configuring the first electrical element E1 using the transistors TR1 to TR4 (or TR5 to TR8), the capacitance changing functional units 13C to 13F can be configured easily and inexpensively with a smaller number of parts. Can do.

  Moreover, in the voltage measuring apparatus 1 described above, the current detector 15 is configured using a resistor. However, as long as it is an impedance element, the current detector 15 can be configured not only by a resistor but also by a capacitor or a coil, or a combination thereof. It can also be configured. By using the impedance element in this way, the voltage value of the voltage V2 generated when the current i flows can be arbitrarily changed by changing the impedance value of the impedance element. For this reason, as a result that the voltage V2 generated in the current detector 15 can be set to an appropriate value according to the level of the voltage V1 of the measurement object 4, the measurement object 4 can be set over a wide voltage range from a low voltage to a high voltage. Can be accurately measured. Similarly to the current i flowing through the capacitance change function body 13, the voltage across the capacitance change function body 13 is also the voltage V1 of the measurement object 4 and the reference potential (the potential of the case 11, that is, the feedback voltage V4). It changes in proportion to the potential difference. For this reason, although not shown, a configuration in which the voltage between both ends of the capacitance change function bodies 13, 13A,..., 13F is detected by the preamplifier 16 and output as the detection signal S3 without providing the current detector 15 is provided. It can also be adopted.

1 is a block diagram of a voltage measuring device 1. FIG. 3 is a circuit diagram of a capacity change function body 13. FIG. 6 is a relationship diagram between a drive signal S2 and a capacitance C2 for explaining the operation of the capacitance change function body 13. FIG. It is a circuit diagram of capacity change functional body 13A. It is a circuit diagram of capacity change functional body 13A-1. It is a circuit diagram of capacity change function body 13B. It is a circuit diagram of capacity change functional body 13C. It is a circuit diagram of capacity change functional body 13D. It is a circuit diagram of capacity change function body 13E. It is a circuit diagram of capacity change function body 13F. It is a wave form diagram after calibration of detection signal S3. 2 is a block diagram of a variable capacitance circuit 19 and its peripheral circuits that have already been developed by the inventor of the present application. FIG. FIG. 13 is a waveform diagram of a detection signal S3 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Voltage measuring apparatus 2 Probe unit 3 Main body unit 4 Measurement object 11 Case 12 Detection electrode 13, 13A, 13A-1, 13B-13G Capacitance change functional body 14 Drive circuit 15 Current detector 19 Variable capacity circuit 25 Voltage generation circuit 31 , 32, 32A, 33, 33A, 33B, 34, 34A Structural unit 71, 71A Adjustment circuit CNT Voltage controller E11 to E14 First electrical element E22, E23 Second electrical element E33, E34 Third electrical element i Current V1 Voltage of measurement object 4 V4 Feedback voltage (reference potential)

Claims (5)

A detection electrode that can be opposed to a measurement object, a variable capacitance circuit that is connected between the detection electrode and a reference potential and is configured to change its capacitance, a voltage generation circuit that generates the reference potential, and the A voltage configured to include a voltage control unit that changes the voltage of the reference potential with respect to the voltage generation circuit when the variable capacitance circuit is changing the capacitance, so that the voltage of the measurement object can be measured. A measuring device,
The variable capacitance circuit includes two first elements that function as a resistor when one end is at a high potential with respect to the other end, and that function as a capacitor when the one end is at a low potential with respect to the other end. A first structural unit, a second structural unit, a third structural unit, and a fourth structural unit each including a first electrical element configured in series connection in the opposite direction are connected in a ring shape in this order. The connection point of the first structural unit and the fourth structural unit is connected to the detection electrode, and the connection point of the second structural unit and the third structural unit is connected to the reference potential. An alternating voltage is applied between the capacitance changing functional unit, the connection point of the first structural unit and the second structural unit, and the connection point of the third structural unit and the fourth structural unit. Drive operation to change the capacitance of the capacitance change function body. A resistance component between a connection point of the first structural unit and the second structural unit and a connection point of the second structural unit and the third structural unit, and the second structural unit and Voltage measurement configured to include a variable resistance circuit that changes a ratio of resistance components between the connection point of the third structural unit and the connection points of the third structural unit and the fourth structural unit. apparatus. A detection electrode that can be opposed to a measurement object, a variable capacitance circuit that is connected between the detection electrode and a reference potential and is configured to change its capacitance, a voltage generation circuit that generates the reference potential, and the A voltage configured to include a voltage control unit that changes the voltage of the reference potential with respect to the voltage generation circuit when the variable capacitance circuit is changing the capacitance, so that the voltage of the measurement object can be measured. A measuring device,
The variable capacitance circuit includes a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit that are annularly connected in this order, and the first structural unit and the first structural unit. The four constituent elements 4 function as a resistor when one end is at a high potential with respect to the other end, and the two first elements that function as a capacitor when the one end is at a low potential with respect to the other end are reversed. Each including a first electrical element configured in series connection in a direction, each of the second structural unit and the third structural unit including a second electrical element that allows passage of an AC signal; and A capacitor in which a connection point of the first structural unit and the fourth structural unit is connected to the detection electrode, and a connection point of the second structural unit and the third structural unit is connected to the reference potential A change function body and the first structural unit And driving to change the capacitance of the capacitance change function body by applying an AC voltage between the connection point of the second structural unit and the connection point of the third structural unit and the fourth structural unit. A circuit, a resistance component between a connection point of the first structural unit and the second structural unit and a connection point of the second structural unit and the third structural unit, and the second structural unit And a variable resistance circuit that changes the ratio of the resistance component between the connection point of the third structural unit and the connection point of the third structural unit and the fourth structural unit. measuring device. A detection electrode that can be opposed to a measurement object, a variable capacitance circuit that is connected between the detection electrode and a reference potential and is configured to change its capacitance, a voltage generation circuit that generates the reference potential, and the A voltage configured to include a voltage control unit that changes the voltage of the reference potential with respect to the voltage generation circuit when the variable capacitance circuit is changing the capacitance, so that the voltage of the measurement object can be measured. A measuring device,
The variable capacitance circuit includes a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit that are annularly connected in this order, and the second structural unit and the second structural unit. The two first elements that function as a resistor when one end of the three structural units has a high potential with respect to the other end and that function as a capacitor when the one end has a lower potential with respect to the other end are reversed. A third electrical element that includes first electrical elements that are connected in series in a direction, and that allows the first structural unit and the fourth structural unit to pass an AC signal while preventing the passage of a DC signal. Each of the electrical components is included, and the connection points of the first structural unit and the fourth structural unit are connected to the detection electrode, and the connection points of the second structural unit and the third structural unit are Capacitance changing function connected to the reference potential And applying the alternating voltage between the connection point of the first structural unit and the second structural unit and the connection point of the third structural unit and the fourth structural unit, the capacitance changing function body And a resistance component between a connection point of the first structural unit and the second structural unit and a connection point of the second structural unit and the third structural unit And a variable resistance circuit for changing a ratio of resistance components between the connection point of the second structural unit and the third structural unit and the connection point of the third structural unit and the fourth structural unit A voltage measuring device comprising: A detection electrode that can be opposed to a measurement object, a variable capacitance circuit that is connected between the detection electrode and a reference potential and is configured to change its capacitance, a voltage generation circuit that generates the reference potential, and the A voltage configured to include a voltage control unit that changes the voltage of the reference potential with respect to the voltage generation circuit when the variable capacitance circuit is changing the capacitance, so that the voltage of the measurement object can be measured. A measuring device,
The variable capacitance circuit includes a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit that are annularly connected in this order, and the first structural unit and the first structural unit A resistor when one end of each set of the set of 2 set units and the set of the set 3 set units and the set 4 set units is at a higher potential than the other end Each of which includes a first electrical element configured by connecting two first elements that function as a capacitor when the one end is at a low potential relative to the other end in series in a reverse direction, Each of the other structural units includes a third electrical element that allows the passage of the alternating current signal while preventing the passage of the direct current signal, and the connection point between the first structural unit and the fourth structural unit is The second structural unit and the second unit are connected to the detection electrode A capacitance change function body in which the connection point of the structural unit is connected to the reference potential, the connection point of the first structural unit and the second structural unit, the third structural unit, and the fourth structural unit A driving circuit that changes an electrostatic capacity of the capacitance change function body by applying an AC voltage between the first structural unit and the second structural unit, and the second structural unit. The resistance component between the structural unit and the connection point of the third structural unit, and the connection point of the second structural unit and the third structural unit, the third structural unit, and the fourth structural unit And a variable resistance circuit that changes a ratio of a resistance component between the connection point and the voltage measuring device.   5. The voltage measuring apparatus according to claim 1, wherein the first element includes a diode formed of a P-type semiconductor and an N-type semiconductor.

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