JP2007256141A - Voltage detection device and initialization method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage detection device for accurately detecting the voltage of a measured object. <P>SOLUTION: The voltage detection device 1, constituted to detect the voltage V1 between a reference potential (ground) and the measured object 4, comprises a detection electrode 12 opposite to the measured object 4; a variable capacity circuit 19 constituted to vary the electrostatic capacity C1 by being connected to the detection electrode 12; a potential body 28, regulated to the reference potential by potential and opposite to the detection electrode 12; and a connection circuit 51 for electrically connecting the detection electrode 12 to the reference potential. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a voltage detection apparatus and an initialization method that can measure the voltage of a measurement object in a non-contact manner.

  As this type of voltage detection device, the inventor of the present application disclosed various voltage detection devices in Japanese Patent Application Nos. 2005-297171, 2005-341388, 2005-363283, and 2005-365666 (specific examples). Discloses a voltage measuring device.

  Each of these voltage detection devices includes a detection electrode that can be opposed to a measurement object, a variable capacitance circuit that is connected between the detection electrode and the reference potential and can change its capacitance, and a reference potential. And a 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. In these voltage detection devices, when the variable capacitance circuit changes the capacitance, the control unit detects the current flowing through the variable capacitance circuit (or the voltage across the variable capacitance circuit), while the voltage generation circuit The reference potential when the detected current (or the voltage between both ends) becomes zero is changed to the voltage of the object to be measured (voltage based on the reference potential, in other words, the reference potential The voltage is measured (specifically, measured) as a voltage between the measurement object and the object to be measured.

According to these voltage detection devices, for example, unlike the voltage measurement devices disclosed in JP-A-4-305171 and JP-A-7-244103, detection is performed between the variable capacitance circuit and the measurement object. Due to the configuration in which the electrode (fixed electrode) is arranged, for example, by arranging this detection electrode on the outer surface of the probe unit, the variable capacitance circuit is arranged inside the probe unit without being exposed to the outside. Can do. Therefore, since the detection electrode can prevent erroneous insertion of foreign matter into the probe unit, the reliability of the apparatus can be improved. Further, since the variable capacitance circuit is composed of components that operate electrically, a mechanical component for changing the capacitance can be eliminated. Therefore, the reliability of the apparatus can be improved also by this.
Japanese Patent Laid-Open No. 4-305171 (page 2, FIG. 6) JP 7-244103 A (2nd page, FIG. 9)

  However, as a result of further examination of each of the voltage measuring devices disclosed by the present inventor, the present inventors have found that these voltage measuring devices have the following problems to be solved. I found it. That is, in any voltage measuring device, when the detection electrode is not charged (when the initial charge of the detection electrode is zero), the voltage of the measurement object can be accurately measured, but the detection electrode is charged. When the measurement is performed (when the initial charge is not zero), there is a problem that an error occurs in the measured voltage of the measurement object due to charging.

  The present invention has been made to solve the above-described problems, and a main object of the present invention is to provide a voltage detection device and an initialization method that can accurately detect the voltage of a measurement object.

  In order to achieve the above object, the voltage detection device according to claim 1 is a voltage detection device configured to be able to detect a voltage between a reference potential and a measurement object, and capable of detecting the voltage to the measurement object. An electrode, a variable capacitance circuit configured to be connected to the detection electrode and capable of changing its capacitance, a potential body whose potential is defined by the reference potential and can be opposed to the detection electrode, and the detection electrode And a connection circuit that can be electrically connected to the reference potential.

  The voltage detection device according to claim 2 is the voltage detection device according to claim 1, wherein the variable capacitance circuit is connected between the detection electrode and a reference potential to generate the reference potential. And a 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.

  The voltage detection device according to claim 3 is a voltage detection device configured to be able to detect a voltage between a reference potential and a measurement object, and the detection electrode capable of facing the measurement object; A variable capacitance circuit connected between the detection electrode and the reference potential and configured to change its capacitance, a voltage generation circuit for generating the reference potential, and the variable capacitance circuit configured to change the capacitance. A control unit that changes the voltage of the reference potential with respect to the voltage generation circuit when the voltage is changed, a potential body that is regulated by the reference potential and can be opposed to the detection electrode, and the detection electrode. A connection circuit electrically connectable to the reference potential.

  According to a fourth aspect of the present invention, there is provided an initialization method comprising: a detection electrode that can be opposed to a measurement object; and a variable capacitance circuit that is connected to the detection electrode and configured to change its capacitance, With respect to a voltage detection device configured to be able to detect a voltage between the measurement object and the measurement object, in a state where the detection electrode is disposed to face a potential body whose potential is defined by the reference potential, The detection electrode is temporarily electrically connected to the reference potential.

  In addition, the initialization method according to claim 5 includes a detection electrode that can be opposed to a measurement object, a variable capacitor that is connected between the detection electrode and a reference potential, and that can change its capacitance. A circuit, a voltage generation circuit that generates the reference potential, and a 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 state in which the detection electrode is arranged opposite to a potential body whose potential is defined as the reference potential with respect to a voltage detection device configured to be able to detect a voltage between a reference potential and the measurement object The detection electrode is temporarily electrically connected to the reference potential.

  According to the voltage detection device of claim 1 and the initialization method of claim 4, in the state where the detection electrode is arranged to face the potential body whose potential is defined as the reference potential, the detection electrode is connected by the connection circuit. By temporarily electrically connecting to the reference potential, the charge charged on the detection electrode can be discharged. In this case, when the detection electrode is positively or negatively charged, since the detection electrode faces a potential body having the same potential as the reference potential, the charge of the positive charge and the negative charge charged on the detection electrode One charge having a large amount is moved away by the repulsive force of the potential body, and as a result, flows out to the reference potential until it becomes equal to the other charge amount. For this reason, the detection electrode is in a state where the positive charge and the negative charge are balanced (equivalently, the charge is zero). Therefore, according to the voltage measuring device and the initialization method, the charge of the detection electrode is surely initialized to zero (a state where positive and negative charges are balanced) as compared with a configuration in which the detection electrode is simply connected to the reference potential. Can be As a result, according to this voltage measuring apparatus, since the initial charge of the detection electrode can be zero (the detection electrode is not charged), the voltage measurement process for the measurement object can always be started. The influence caused by the charging of the detection electrode can be avoided, and thereby the voltage of the measurement object can always be detected (measured) accurately.

  According to the voltage detection device of the second aspect, the variable capacitance circuit is connected between the detection electrode and the reference potential, and the voltage generation circuit for generating the reference potential and the variable capacitance circuit have the capacitance. By providing a control unit that changes the voltage of the reference potential with respect to the voltage generation circuit when the voltage is changed, a current (or variable capacitance) generated (flowing) in the variable capacitance circuit when the capacitance of the variable capacitance circuit changes The voltage of the reference potential when this current (or the voltage across the terminal) becomes zero ampere (or zero volts) while detecting the voltage across the circuit) Can be measured with high accuracy.

  According to the voltage detection device of claim 3 and the initialization method of claim 5, in a state where the detection electrode is arranged to face the potential body whose potential is defined as the reference potential, the detection electrode is connected by the connection circuit. By temporarily electrically connecting to the reference potential, the charge charged on the detection electrode can be discharged. In this case, when the detection electrode is positively or negatively charged, since the detection electrode is opposed to a potential body having the same potential as the reference potential, the charge of the positive charge and the negative charge charged to the detection electrode One charge having a large amount is moved away by the repulsive force of the potential body, and as a result, flows out to the reference potential until it becomes equal to the other charge amount. For this reason, the detection electrode is in a state where the positive charge and the negative charge are balanced (equivalently, the charge is zero). Therefore, according to the voltage measuring apparatus and the initialization method, the charge of the detection electrode is surely initialized to zero (a state where positive and negative charges are balanced) as compared with a configuration in which the detection electrode is simply connected to the reference potential. Can be As a result, according to this voltage measuring apparatus, since the initial charge of the detection electrode can be zero (the detection electrode is not charged), the voltage measurement process for the measurement object can always be started. The influence caused by the charging of the detection electrode can be avoided, and thereby the voltage of the measurement object can always be detected (measured) accurately.

  The best mode of a voltage detection apparatus according to the present invention will be described below with reference to the accompanying drawings. As an example of the voltage detection device, a voltage measurement device that measures the voltage of the measurement object will be described as an example.

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

  As shown in FIG. 1, the voltage measuring device 1 includes a probe unit 2 and a main body unit 3, and is configured to be able to measure the voltage (alternating voltage) V <b> 1 of the measurement object 4 without contact.

  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, a preamplifier 16, and a switch 51, and the main unit 3 via a flexible cable 52. It is connected to the. 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.

  As illustrated in FIG. 1, the variable capacitance circuit 19 includes one capacitance change function body 13 and one drive circuit 14. 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. And is configured as a so-called bridge circuit (annular circuit). Specifically, as shown in FIG. 2, each of the structural units 31, 32, 33, and 34 includes first electrical elements E11, 12, 13, and 14 (hereinafter referred to as “first electrical element E1 unless otherwise distinguished”). 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 example, as an example, each first element 41 is configured to include a P-type semiconductor and an N-type semiconductor that are joined to each other, and more specifically, one diode (for example, a variable capacitance diode; a varicap or a varactor). Each first electric element E1 is formed 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 impedance product of the unit 32 and the fourth structural unit 34 is set to be the same or substantially the same (for example, a state that is different within a range of about several percent).

  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 it is configured, although not shown in the drawing, the first electric elements E1 are configured by connecting the other ends of the pair of first elements 41a and 41b (connecting the cathode terminals of the pair of diodes). You can also 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. For this reason, although not shown in the figure, it is also possible to configure a capacitance change function body by replacing all of the first elements 41a and 41b in the capacitance change function body 13 with general diodes.

  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 the drive signal S1 input from the main unit 3 via the cable 52 is electrically insulated from the drive signal S1. At the same time, it is converted into a drive signal S2 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, the frequency f1 of the drive signal S1 is set extremely high compared to the frequency of the voltage V1. 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. The primary winding 14b of the transformer 14a is excited based on the signal S1, and the drive signal S2 is generated in the secondary winding 14c. With this configuration, the drive circuit 14 converts the drive signal S1 into the drive signal S2 with low distortion, and applies the drive signal S2 between the connection points B and D of the capacitance change function body 13. In this example, since a sine wave signal is used as the drive signal S1 as an example as described later, the drive signal S2 is also output as a sine wave signal. Instead of the drive circuit 14, a floating signal source (not shown) that outputs the drive signal S2 alone (without inputting the drive signal S1 from the main unit 3) is provided in the probe unit 2. You can also

  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 to the capacitance changing function body 13 of the variable capacitance circuit 19. A current i (physical quantity) is detected, and 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). The preamplifier 16 amplifies the voltage V2 input through the capacitor by the amplifier circuit, converts the amplified voltage into a detection signal S3 electrically insulated from the amplifier circuit by the insulating electronic component, and outputs the detection signal S3. To do. 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.

  The switch 51 forms a connection circuit according to the present invention, and is connected between the detection electrode 12 (in this example, the connection point A of the capacitance change function body 13) and the reference potential (case 11). In this example, the switch 51 is constituted by a momentary push button switch as an example, and is arranged to be operable from the outside of the probe unit 2. In this case, the case 11 is connected to the feedback voltage V4 supply line (at least one conductor (not shown) in the cable 52) and the voltage generation circuit 25 in the voltage generation circuit 25 shown in FIG. It is connected to the ground as a reference potential. Here, the voltage generation circuit 25 that outputs the feedback voltage V4 outputs the feedback voltage V4 with a predetermined impedance (output impedance Z1) with reference to the ground. For this reason, the connection point A of the probe unit 2 is connected to the ground (reference potential) through a series circuit of the switch 51, the cable 52, and the output impedance Z1 of the voltage generation circuit 25. Therefore, when the switch 51 shifts from the off state to the on state, the connection point A is connected to the reference potential via the switch 51 and the like.

  As shown in FIG. 1, the main unit 3 includes an oscillation circuit 21, an amplification circuit 22, a synchronous detection circuit 23, an integrator 24, a voltage generation circuit 25, a voltmeter 26, a filter circuit 27, and a potential body 28. ing. The oscillation circuit 21 generates a drive signal S1 having a constant period T1 (frequency f1) and outputs the drive signal S1 to the probe unit 2 via the cable 52, and also has a half period T2 (frequency (2 × f1) of the period T1. ) Is generated in synchronization with the drive signal S1 and output to the synchronous detection circuit 23. In this case, in this example, the oscillation circuit 21 generates a sine wave signal as the drive signal S1 and the detection signal S11. The filter circuit 27 selectively allows a signal S3a having the same frequency as the capacitance modulation frequency of the capacitance change function body 13 included in the detection signal S3 input from the probe unit 2 via the cable 52 to pass therethrough.

  The amplifier circuit 22 amplifies the signal S3a input from the filter circuit 27 to a preset voltage level and outputs the amplified signal as a detection signal S4. In this example, the capacity modulation frequency of the capacity changing function body 13 is a frequency f2 that is twice the frequency f1 of the drive signal S2. For this reason, the frequency of the current i generated by the change in the capacitance C1 is also a frequency f2 that is twice the frequency f1 of the drive signal S1. Although the component is included, the frequency of the detection signal S4 output from the amplifier circuit 22 becomes f2 by filtering by the filter circuit 27. The synchronous detection circuit 23 is configured to generate the pulse signal S5 by synchronously detecting the detection signal S4 with the detection signal S11. In this case, the amplitude of the pulse signal S5 changes in proportion to the value of the current i flowing through the variable capacitance circuit 19, and the polarity changes according to the direction of the current i flowing through the variable capacitance circuit 19.

  The integrator 24 continuously integrates the pulse signal S5 to generate a DC voltage V3 and outputs it to the voltage generation circuit 25. In this example, as an example, the integrator 24 is set to output a DC voltage V3 of zero volts until the first pulse signal S5 is input after the integration operation is started. These filter circuit 27, amplifier circuit 22, synchronous detection circuit 23, and integrator 24 constitute a control unit CNT to control 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 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 and displays the voltage value. The potential body 28 is formed, for example, in a flat plate shape and disposed (fixed) on the outer surface of the main unit 3. The potential body 28 is connected to the ground as a reference potential inside the main unit 3.

  Next, the measuring operation of the voltage measuring device 1 will be described together with the measuring method of the voltage (AC voltage) V1 of the measuring object 4 using the voltage measuring device 1. In order to facilitate understanding of the invention, the voltage V1 is described as being in the positive voltage period as an example. However, when the voltage V1 is in the negative voltage period, the polarity of the corresponding signal or voltage is reversed. The measurement is performed in the same manner as in the positive voltage period except that.

  First, prior to the measurement of the voltage V1, an initialization (reset) process for discharging the charge charged on the detection electrode 12 is executed. In this initialization process, first, the probe unit 2 is moved to the vicinity of the main unit 3 so that the detection electrode 12 is opposed to the potential body 28 of the main unit 3 in a non-contact state. Next, the switch 51 of the probe unit 2 is operated to temporarily shift the switch 51 from the off state to the on state. As a result, the detection electrode 12 (connection point A of the probe unit 2) is connected to the ground (reference potential) via the switch 51, the case 11, the cable 52, and the output impedance Z1 of the voltage generation circuit 25 in the ON state. Is done. In this case, when the detection electrode 12 is positively or negatively charged, since the detection electrode 12 faces the potential body 28 having the same potential as the ground, the positive and negative charges charged in the detection electrode 12 are charged. One of the charges having a large charge amount is moved away by the repulsive force of the potential body 28, and flows out to the ground through the series circuit including the switch 51 until it becomes equal to the other charge amount. Therefore, the detection electrode 12, that is, the portion between the detection electrode 12 and the capacitance changing function body 13 is in a state where the positive charge and the negative charge are balanced (equivalently, the charge is zero). Thereby, the initialization process is completed.

  Subsequently, a measurement process of the voltage V1 is executed. In this measurement process, first, the probe unit 2 is arranged in the vicinity of the measurement object 4 so that the detection electrode 12 faces the measurement object 4 in a non-contact state. 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 changes in inverse proportion to the distance between the detection electrode 12 and the measuring object 4, but once the probe unit 2 is disposed, the capacitance value is constant (does not vary). . Moreover, the initial charge of the detection electrode 12 (the connection point A of the probe unit 2) is in a zero state by the initialization process.

  Next, in the activated state of the voltage measuring apparatus 1, in the main unit 3, the oscillation circuit 21 starts generating the drive signal S1 and the detection signal S11, and the drive signal S1 is sent to the probe unit 2 and the detection signal S11 is sent. Output to the synchronous detection circuit 23. 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.

  In the capacity change function body 13, the drive signal S <b> 2 applied between the connection points B and D is divided, and the first structural unit 31, the second structural unit 32, the third structural unit 33 and the fourth structural unit 13. Applied to each of the structural units 34. 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 electrical elements E11 and E14, and each of the first electrical 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 becomes 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 electric element E11, E14, and each electrostatic element in each first element 41b in each first electric element E12, E13. The capacity gradually decreases. In addition, 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. In each of the first elements, specifically, in each of the first electric elements E11 and E14, each of the first elements 41a, and in each of the first electric elements E12 and E13, each electrostatic capacity of each of the first elements 41b gradually increases. 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 electric element E1 repeats decreasing and increasing twice within one cycle T1 of the drive signal S2.

  In this way, 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, the variable capacitance circuit 19 is disposed (connected) between the case 11 and the detection electrode 12 in a state of being connected in series with the current detector 15, so that the capacitance thereof C1 and the capacitance C0 formed between the measurement object 4 and the detection electrode 12 are connected in series between the measurement object 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.

  In the variable capacitance circuit 19, as described above, variable capacitance diodes (or general diodes) having the same or substantially the same characteristics are used for the first elements 41 of the capacitance change function body 13, and as a result, The products of the impedances of the first structural unit 31 and the third structural unit 33 and the products of the impedances of the second structural unit 32 and the fourth structural unit 34 are set to be the same or substantially the same. Therefore, since the capacitance changing function body 13 which is also a bridge circuit satisfies the equilibrium condition as the bridge circuit, the voltage component of the drive signal S2 (the voltage signal having the same frequency f1 as the drive signal S1) is connected to each connection point A, The electrostatic capacity C1 is changed with the period T2 in a state where there is almost no generation between C. Also included in each set of first electrical elements E11 and E14 included in each of the structural units 31 and 34 connected to the connection point A and included in each of the structural units 32 and 33 connected to the connection point C. Since the two first electric elements E1 included in at least one of the first electric elements E12 and E13 are always functioning as a capacitor, the detection electrode 12 and the case 11 is connected in an AC manner through the variable capacitance circuit 19 but is maintained in a state where it is not short-circuited in a DC manner.

  Further, since the integrator 24 of the main unit 3 outputs a DC voltage V3 of zero volts immediately after the operation of the voltage measuring device 1, the voltage generation circuit 25 is configured to output a feedback voltage V4 of a predetermined voltage (for example, from the voltage V1). Is also a low voltage, which is approximately zero volts) and applied to the case 11 of the probe unit 2. For this reason, a potential difference (V1−V4) is generated between the measurement object 4 and the case 11. Therefore, as described above, the capacitance C2 between the measurement object 4 and the case 11 periodically changes in the cycle T2 based on the periodic change in the cycle C2 of the capacitance C1. A current i flows through the variable capacitance circuit 19 while changing the current value at the period T2. In this case, the current i has a large current value when the potential difference (V1-V4) is large, and a small current value when the potential difference (V1-V4) is small. The current i flows from the detection electrode 12 toward the current detector 15 when the polarity of the potential difference (V1-V4) is positive, and flows in the reverse direction when the polarity of the potential difference (V1-V4) is negative.

  In this example, the voltage V1 is in a positive voltage period and starts from a state where the feedback voltage V4 is lower than the voltage V1 (for example, zero volts), so that the potential difference (V1-V4) is always a voltage of zero volts or more. Therefore, in this example, the current i always flows from the detection electrode 12 toward the current detector 15 while changing the current value at the period T2. Since the voltage V1 is an AC voltage, the current i changes its current value even if the voltage V1 changes, but the frequency f1 of the drive signal S1 is extremely higher than the frequency of the voltage V1, and the capacitance Since the capacity modulation frequency f2 of the change function body 13 is also extremely higher than the frequency of the voltage V1, the change due to the change of the voltage V1 can be ignored when viewed in a short period.

  The preamplifier 16 outputs a positive polarity detection signal S3 to the main unit 3 by amplifying the voltage V2 generated across the current detector 15 due to the current i. In this case, the detection signal S3 mainly includes the same frequency component as the frequency f2 of the current i.

  In the control unit CNT of the main unit 3, the filter circuit 27 selectively outputs the signal component of the frequency f2 included in the detection signal S3 as the signal S3a, and the amplifier circuit 22 amplifies and detects the signal S3a. A signal S4 is generated and output to the synchronous detection circuit 23. Next, the synchronous detection circuit 23 generates a pulse signal S5 by synchronously detecting the input detection signal S4 with the detection signal S11 and outputs the pulse signal S5 to the integrator 24. Subsequently, the integrator 24 continuously integrates the pulse signal S <b> 5 to generate a DC voltage V <b> 3 and outputs it to the voltage generation circuit 25. In this case, as described above, in this example, since the detection signal S3 is always a positive signal, and similarly, the detection signal S4 is also a positive signal, the pulse signal S5 is always a positive pulse signal. Become. As a result, the voltage value of the DC voltage V3 output from the integrator 24, that is, the control unit CNT, gradually increases. Therefore, the feedback voltage V4 generated by the voltage generation circuit 25 also gradually increases toward the voltage V1, as shown in FIG. As a result, in the feedback loop composed of the current detector 15, preamplifier 16, filter circuit 27, amplifier circuit 22, synchronous detection circuit 23, integrator 24 and voltage generation circuit 25, the measurement object 4 and the case 11 Negative feedback is performed so that the potential difference (V1-V4) decreases gradually (decreases). Therefore, the current value of the current i gradually decreases (decreases).

  Thereafter, when the feedback voltage V4 reaches the voltage V1, the potential difference (V1-V4) becomes zero volts. In this state, even if the capacitance C2 between the measurement object 4 and the case 11 changes periodically, the current i does not flow. Further, since the current i does not flow, the voltage V2 is not generated in the current detector 15 (the voltage V2 becomes zero volts). As a result, the detection signal S3 is not output from the preamplifier 16. Further, since the detection signal S3 is not output, the detection signal S4 is not output from the amplifier circuit 22, and the output of the pulse signal S5 from the synchronous detection circuit 23 is also stopped. As a result, the direct current output from the integrator 24 is stopped. As a result of stopping the increase of the voltage V3 and stopping the increase of the feedback voltage V4 output from the voltage generation circuit 25, the feedback voltage V4 is maintained at the voltage V1, as shown in FIG. In this way, the feedback voltage V4 follows the voltage V1. Therefore, by observing the voltage value (feedback voltage V4) displayed on the voltmeter 26, the voltage (voltage between the ground and the measurement object 4) V1 of the measurement object 4 is measured.

  As described above, in the voltage measuring device 1 and the initialization method of the voltage measuring device 1, the switch 51 is placed in a state where the detection electrode 12 is disposed opposite to the potential body 28 whose potential is defined as the reference potential (ground). To electrically connect the detection electrode 12 to the reference potential temporarily, thereby discharging the charge charged in the detection electrode 12. In this case, when the detection electrode 12 is positively or negatively charged, since the detection electrode 12 faces the potential body 28 having the same potential as the ground (reference potential), the positive charge charged in the detection electrode 12 One of the negative charges having a large charge amount is moved away by the repulsive force of the potential body 28 and flows out to the ground until it becomes equal to the other charge amount. Therefore, the detection electrode 12 is in a state where the positive charge and the negative charge are balanced (equivalently, the charge is zero). Therefore, according to the voltage measurement device 1 and the initialization method of the voltage measurement device 1, the charge of the detection electrode 12 (the connection point A of the probe unit 2) is compared with a configuration in which the detection electrode 12 is simply connected to the reference potential. Can be reliably initialized to zero (a state where positive and negative charges are balanced). Further, according to this voltage measuring apparatus 1, since the measurement process of the voltage V1 can always be started from the state where the initial charge of the detection electrode 12 is zero (the detection electrode 12 is not charged), the detection electrode 12 can be avoided, and the voltage V1 of the measurement object 4 can always be accurately measured.

  Further, according to the voltage measuring apparatus 1, the variable capacitance circuit 19 is connected between the detection electrode 12 and the reference potential (case 11), and the voltage generation circuit 25 that generates the reference potential (feedback voltage V4) is provided. The variable capacitance circuit 19 (specifically, the capacitance change function body 13) includes a control unit CNT that changes the feedback voltage V4 with respect to the voltage generation circuit 25 when the capacitance C1 is changed. While detecting the current i generated (flowing) in the variable capacitance circuit 19 when the capacitance of the variable capacitance circuit 19 is changed, the voltage of the feedback voltage V4 when the current i becomes zero ampere is the voltage of the measurement object 4. By measuring as V1, the voltage V1 of the measuring object 4 can be measured with high accuracy.

  In addition, this invention is not limited to said structure. For example, in the capacitance changing function body 13 of the variable capacitance circuit 19 in the voltage measuring device 1 described above, as shown in FIG. 2, all the structural units 31 to 34 are configured to include the first electrical elements E11 to E14, respectively. However, the present invention is not limited to this, and in the capacity change function body 13 shown in the figure, the first structural unit 31 and the fourth structural unit among the first to fourth structural units 31 to 34 are included. 34 and the first electrical element included in each structural unit of one of the second structural unit 32 and the third structural unit 33 are allowed to pass an AC signal. The capacitance changing function body can be configured by replacing the second electric element. 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. 5 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.

  Moreover, in the capacity | capacitance change function body 13 of the voltage measuring device 1 shown in FIG. 2, the group of the 1st structural unit 31 of the 1st-4th structural units 31-34, and the 2nd structural unit 32, and The first electrical element E1 included in each structural unit of one set of the third structural unit 33 and the fourth structural unit 34 is configured to prevent the passage of the direct current signal while preventing the passage of the direct current signal. The capacitance changing function body can be configured by replacing with a third electrical element that allows passage. 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).

  Even in the configuration employing each of the capacitance changing functional bodies 13A and 13B described above, by providing the potential body 28 and the switch 51 as described above, the initial charge of the detection electrode 12 is zero (the detection electrode 12 is charged). Since the measurement process of the voltage V1 can always be executed from the state (not in the state), the voltage V1 of the measurement object 4 can always be measured accurately.

  Further, in the voltage measuring apparatus 1 shown in FIG. 1, the current detector 15 is provided, and the preamplifier 16 converts the voltage V2 generated at both ends of the current detector 15 due to the current i into the detection signal S3. The preamplifier 16 detects the voltage across the variable capacitance circuit 19 (specifically, the capacitance changing function body 13), converts it into the detection signal S3, and outputs the detection signal S3. You can also Also in this configuration, the potential body 28 and the switch 51 are provided in the same manner as the voltage measuring device 1 described above, so that the initial charge of the detection electrode 12 is zero (the detection electrode 12 is not charged). Since the measurement process of the voltage V1 can always be executed, the voltage V1 of the measurement object 4 can always be accurately measured.

  Further, in the voltage measuring apparatus 1, when the variable capacitance circuit 19 changes the capacitance C1, the voltage of the part (case 11 in this example) where the control unit CNT becomes a reference potential with respect to the voltage generation circuit 25. (Feedback voltage V4) is adopted, and when the feedback voltage V4 coincides with the voltage V1 of the measurement object 4, the current i flowing through the variable capacitance circuit 19 or the voltage across the variable capacitance circuit 19 is obtained. Is used to measure the voltage V1 of the measurement object 4, but when the existence range of the voltage V1 of the measurement object 4 is known in advance, instead of the feedback control method, The main unit can also be configured using an open control system. Specifically, when the variable capacitance circuit 19 is changing the capacitance C1, the control unit outputs the output voltage to the voltage generation circuit from the lower limit value to the upper limit value of the existence range of the voltage V1 ( Or from the upper limit value to the lower limit value), the current i flowing through the variable capacitance circuit 19 or the output voltage of the voltage generation circuit when the voltage across the variable capacitance circuit 19 becomes almost zero is detected. The main body unit can also be configured to specify this output voltage as the voltage V1 of the measurement object 4.

  Further, the example in which the variable capacitance circuit 19 is applied to the voltage measurement apparatus 1 that measures the voltage of the measurement object 4 has been described above. However, the variable capacitance circuit 19 is interposed between the measurement object 4 and a portion that serves as a reference potential (case 11 in this example). When there is a potential difference, the current i always flows through the variable capacitance circuit 19 when the variable capacitance circuit 19 changes the capacitance C1, and the voltage across the variable capacitance circuit 19 is not zero. By utilizing this, the variable capacitance circuit 19 can be applied to a voltage detector as an example of a voltage detection device. Even in this case, by arranging the potential body 28 and the switch 51, the measurement process of the voltage V1 is always executed from the state where the initial charge of the detection electrode 12 is zero (the detection electrode 12 is not charged). Therefore, it is always possible to accurately detect whether or not the voltage of the measurement object 4 is different from the reference potential.

  Further, although the example in which the potential body 28 is disposed in the main body unit 3 has been described above, a configuration in which the potential body 28 is separated from the main body unit 3 may be employed. In addition, the present invention is not limited to the voltage measuring device 1 provided with each capacitance change function body 13 described above, and all voltage detections including the detection electrode 12 and the probe unit 2 provided with the capacity change function body having other configurations. Of course, it can be applied to the apparatus.

  Further, in each of the voltage detection devices described above, the potential body 28 having the potential as the reference potential is used. However, like the voltage measurement device 1A illustrated in FIG. 7, the potential body 28A having the potential as the reference potential is used. You can also. In this voltage measuring device 1A, as an example, the potential body 28A is connected to the case 11 via the wiring member 53, whereby the potential of the potential body 28A is set as the reference potential. In addition, about the structure same as the voltage measurement apparatus 1, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  Also in the voltage measuring apparatus 1A, by executing the following initialization method prior to the measurement of the voltage V1, the portion between the detection electrode 12 and the capacitance changing function body 13 is charged with a positive charge and a negative charge. It can be initialized to a balanced state (equivalently a state where the charge is zero). Specifically, the potential body 28A is moved to face the detection electrode 12 in a non-contact state, and in this state, the switch 51 of the probe unit 2 is operated to temporarily switch the switch 51 to the on state. Thus, the detection electrode 12 is connected to the case 11 (reference potential) having the same potential as the opposing potential body 28A via the switch 51 in the on state. Therefore, when the detection electrode 12 is positively or negatively charged, one of the positive charge and the negative charge charged to the detection electrode 12 with a large charge amount is moved away by the repulsive force of the potential body 28A. Then, it flows out to the reference potential through the switch 51 until it becomes equal to the other charge amount. Therefore, the detection electrode 12, that is, the portion between the detection electrode 12 and the capacitance changing function body 13 is initialized to a state where the positive charge and the negative charge are balanced (equivalently, the charge is zero).

  Therefore, according to the voltage measurement device 1A and the initialization method of the voltage measurement device 1A, the initial charge of the detection electrode 12 is zero (the detection electrode 12 is charged) in the same manner as the voltage measurement device 1 and the initialization method. The measurement process of the voltage V1 can always be started from the state where the voltage V1 is not measured), so that the influence due to the charging of the detection electrode 12 can be avoided. Can be measured.

1 is a block diagram of a voltage measuring device 1. FIG. 3 is a circuit diagram of a capacity change function body 13 of the voltage measuring device 1. 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 characteristic view which shows the time change of the feedback voltage V4. It is a circuit diagram of capacity change functional body 13A. It is a circuit diagram of capacity change function body 13B. It is a block diagram of voltage measuring device 1A.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A Voltage measuring device 3 Main body unit 4 Measurement object 11 Case 12 Detection electrode 13, 13A, 13B Capacitance change function body 19 Variable capacity circuit 25 Voltage generation circuit 28, 28A Potential body 51 Switch C1 Capacitance CNT control part V1 Voltage of measurement object V4 Feedback voltage (reference potential)

Claims (5)

A voltage detection device configured to be able to detect a voltage between a reference potential and a measurement object,
A detection electrode capable of facing the measurement object;
A variable capacitance circuit connected to the detection electrode and configured to change its capacitance;
A potential body whose potential is defined by the reference potential and capable of facing the detection electrode;
A voltage detection apparatus comprising: a connection circuit capable of electrically connecting the detection electrode to the reference potential. The variable capacitance circuit is connected between the detection electrode and a reference potential;
A voltage generation circuit for generating the reference potential;
The voltage detection circuit according to claim 1, further comprising: a control unit that changes a voltage of the reference potential with respect to the voltage generation circuit when the variable capacitance circuit changes the capacitance. A voltage detection device configured to be able to detect a voltage between a reference potential and a measurement object,
A detection electrode capable of facing the measurement object;
A variable capacitance circuit connected between the detection electrode and a reference potential and configured to change its capacitance;
A voltage generation circuit for generating the reference potential;
A 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;
A potential body whose potential is defined by the reference potential and capable of facing the detection electrode;
A voltage detection circuit comprising: a connection circuit capable of electrically connecting the detection electrode to the reference potential. Detecting a voltage between a reference potential and the measurement object, comprising a detection electrode capable of facing the measurement object and a variable capacitance circuit connected to the detection electrode and configured to change its capacitance For the voltage detector configured to be possible,
An initialization method in which the detection electrode is temporarily electrically connected to the reference potential in a state where the detection electrode is disposed to face a potential body whose potential is defined by the reference potential. 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 that can change its capacitance, and a voltage generation circuit that generates the reference potential And a 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, and between the reference potential and the measurement object. For the voltage detection device configured to detect the voltage,
An initialization method in which the detection electrode is temporarily electrically connected to the reference potential in a state where the detection electrode is arranged to face a potential body whose potential is defined by the reference potential.

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