JP2007212204A - Voltage detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage detector capable of securing sufficient detection accuracy with respect to the voltage of a measurement object. <P>SOLUTION: The voltage detector 1 capable of detecting the voltage V1 of the measurement object 4 with respect to reference potential (ground) includes a detection electrode 12 capable of facing the measurement object 4, a variable capacitance circuit 19 connected to the detection electrode 12 and varying its capacitance C1, and resistances 51, 52, 53, 54 connected between portions (connection points A, B, D, E) made into a floating state with respect to the reference potential and the reference potential (case 11). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a voltage detection apparatus that can detect 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 detected as the voltage of the measurement object (voltage based on the reference potential). Is actually 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 detection devices disclosed by the present inventor, the present inventors have found that these voltage detection devices have the following problems to be solved. I found it. That is, in any voltage detection device, depending on the configuration of the variable capacitance circuit, a part where a DC voltage (DC potential) is not determined with respect to a reference potential, in other words, a part that is in a DC floating state (for example, a detection electrode) ) Is present in the variable capacitance circuit. In this case, since the floating part is easily charged by the surrounding static electricity, the voltage in the variable capacitance circuit becomes unstable, and there is a problem that it is difficult to ensure sufficient detection accuracy for the voltage of the measurement object. Yes.

  The present invention has been made to solve the above-described problems, and has as its main object to provide a voltage detection device that can ensure sufficient detection accuracy for the voltage of the measurement object.

  In order to achieve the above object, the voltage detection apparatus according to claim 1 is a voltage detection apparatus configured to be able to detect a voltage of a measurement object with reference to a reference potential, and capable of detecting the measurement object. An electrode, a variable capacitance circuit configured to be connected to the detection electrode and capable of changing its capacitance, and a resistor connected between the reference potential and a portion that is in a floating state with respect to the reference potential And.

  The voltage detection device according to claim 2 is the voltage detection device according to claim 1, wherein the resistor is connected between the detection electrode and the reference potential.

  According to a third aspect of the present invention, in the voltage detecting device according to the first or second aspect, the resistor is connected between the variable capacitance circuit and the reference potential.

  The voltage detection device according to claim 4 is the voltage detection device according to any one of claims 1 to 3, further comprising a capacitor connected in series between the detection electrode and the variable capacitance circuit, The resistor is connected between the terminal on the variable capacitance circuit side of the capacitor and the reference potential.

  The voltage detection device according to claim 5 is the voltage detection device according to any one of claims 1 to 4, wherein the variable capacitance circuit is connected between the detection electrode 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.

  According to the voltage detection device of claim 1, by connecting a resistor between the reference potential and a portion that is in a floating state with respect to the reference potential, the portion can be brought into a non-floating state, As a result, the entire apparatus can be configured not to be affected by static electricity. For this reason, fluctuations due to static electricity in the voltage of each part in the voltage detection device can be reduced. As a result, fluctuations due to static electricity in the voltage of the detection system can also be reduced, and sufficient detection accuracy is ensured for voltage detection of the measurement object. be able to.

  In addition, according to the voltage detection device of the second aspect, since the resistor is connected between the detection electrode and the reference potential, the detection electrode that is most likely to be in a floating state in the detection system is put into a non-floating state. Therefore, the influence of static electricity on the detection system can be directly reduced (the voltage stability of the detection system can be directly increased), and as a result, the detection accuracy for the voltage detection of the measurement object can be improved. It can certainly be improved.

  According to the voltage detecting device of the third aspect, since the resistor is connected between the variable capacitance circuit and the reference potential, the variable capacitance circuit that is likely to be in a floating state in the detection system is placed in a non-floating state. Therefore, the influence of static electricity on the detection system can be directly reduced (the voltage stability of the detection system can be directly increased), and as a result, the detection accuracy for voltage detection of the measurement object Can be improved more reliably.

  According to the voltage detection device of the fourth aspect, even in the configuration in which the capacitor is connected in series between the detection electrode and the variable capacitance circuit, the resistor is connected between the terminal on the variable capacitance circuit side of the capacitor and the reference potential. By connecting the body, the variable-capacitance circuit-side terminal of the capacitor that may be in a floating state in the detection system can be brought into a non-floating state, thus directly increasing the voltage stability of the detection system. As a result, it is possible to further improve the detection accuracy for voltage detection of the measurement object while protecting the variable capacitance circuit from voltage application due to contact between the measurement object and the detection electrode.

  According to the voltage detection device of the fifth aspect, the variable capacitance circuit is connected between the detection electrode and the reference potential, the voltage generation circuit for generating the reference potential, and the variable capacitance circuit has the electrostatic 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.

  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, a capacitor 20, and resistors 51, 52, 53, and 54. 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 includes a connection point A of the capacitance change function body 13 connected to the detection electrode 12 via the capacitor 20 and a connection point of the capacitance change function body 13. C is connected to the case 11 via the current detector 15. 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 capacitor 20 avoids that the voltage V1 of the measurement object 4 is directly applied to the capacitance change function body 13 when the detection electrode 12 accidentally contacts the measurement object 4, and changes the capacitance due to this voltage application. Damage to the functional body 13 is prevented.

  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 is electrically insulated from the drive signal S1 and the drive signal S1. To the drive signal S2 having the same frequency f1 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 resistors 51, 52, 53, and 54 are resistors having extremely high resistance values (for example, the resistors 51 and 54 are several hundred mega ohms to several hundreds of giga ohms, and the resistors 52 and 53 are equal to each other and are 100 kilo ohms to 10 giga ohms). Thus, the probe unit 2 is connected between a reference potential and a portion in a floating state with respect to a reference potential in the detection system. Specifically, in the probe unit 2, a path from the detection electrode 12 to the preamplifier 16 via the capacitor 20, the variable capacitance circuit 19 (specifically, the capacitance changing function body 13) and the current detector 15 is detected. In this detection system, the connection points A, B, D of the capacitance change function body 13 and the connection point E of the detection electrode 12 and the capacitor 20 are not connected to the resistors 51, 52, 53, 54. In this state, since it is connected only to the capacitor (capacitor 20 and the first structural unit 31 to the fourth structural unit 34), a portion where a DC voltage (DC potential) is not determined with respect to the reference potential, In other words, it becomes a floating state in terms of DC. Accordingly, the resistors 51, 52, and 53 are connected (disposed) between the connection points A, B, and D of the capacitance changing function body 13 as a portion that can be in a floating state and the case 11 (reference potential). Yes. The resistor 54 is connected (arranged) between the connection point E, which is another part that can be in a floating state, and the case 11.

  In this case, the case 11 is connected to the ground as the reference potential in the present invention through the supply line of the feedback voltage V4 in the voltage generation circuit 25 and the voltage generation circuit 25. 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. Therefore, the connection point A of the probe unit 2 that is in a DC floating state is connected to the ground (reference potential) via the series circuit (resistor in the present invention) of the output impedance Z1 of the resistor 51 and the voltage generation circuit 25. ing. Similarly, the other connection points B, D, E of the probe unit 2 which is in a DC floating state are also connected to the series circuit (the resistor in the present invention) of the resistor 52 and the output impedance Z1 of the voltage generation circuit 25, A series circuit of the resistor 53 and the output impedance Z1 of the voltage generation circuit 25 (another resistor in the present invention), and a series circuit of the resistor 54 and the output impedance Z1 of the voltage generation circuit 25 (another resistor in the present invention), respectively. Is connected to the ground. Accordingly, each of the connection points A, B, D, E is in a state of being connected to the reference potential via the corresponding resistor, thereby being in a non-floating state. Note that the connection point C of the capacitance change function body 13 is in a non-floating state because it is connected to the case 11 via a current detector 15 formed of a resistor.

  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, and a filter circuit 27. 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, and also a detection signal having a period T2 (frequency (2 × f1)) that is a half of the period T1. S11 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 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.

  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, when measuring the voltage V1, 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). . In addition, each of the structural units 31, 32, 33, 34 (also a capacitive body) of the capacitance change function body 13 and the capacitor 20 are maintained in a non-floating state by the connection of the resistors 51, 52, 53, 54. Therefore, static electricity is prevented from being charged, and each initial charge is in a substantially zero state.

  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 while being connected in series with the capacitor 20 and the current detector 15. The capacitance C1, the capacitance of the capacitor 20 (referred to as C2), and the capacitance C0 formed between the measurement object 4 and the detection electrode 12 are between the measurement object 4 and the case 11. Are connected in series. For this reason, when the electrostatic capacitance C1 periodically changes at the frequency f2 (capacitance modulation frequency), the electrostatic capacitance C3 between the measurement object 4 and the case 11 (each of the electrostatic capacitances C0, C1, C2). As shown in FIG. 3, the serial composite capacity) also changes in synchronization with the cycle T1 of the drive signal S2 and in a cycle T2 (frequency f2) that 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, each of the resistors 51, 52, 53, 54 is connected to the path from the detection electrode 12 to the current detector 15 (path through which the current i flows). As described above, each of the resistors 51, 52, Since the resistance value of 53, 54 is extremely large, each resistor 51, 52, 53, 54 and a capacitor body to which each resistor 51, 52, 53, 54 is connected (each configuration of the capacitor 20 and the capacitance change function body 13). The time constant with each electrostatic capacity of the units 31, 32, 33, and 34) is also very large. Therefore, a current i having a magnitude corresponding to the potential difference (V 1 −V 4) flows through the variable capacitance circuit 19 without being affected by the connection of the resistors 51, 52, 53, 54. Further, since each part in the path from the detection electrode 12 to the current detector 15 is maintained in a non-floating state due to the connection of the resistors 51, 52, 53, and 54, the influence of static electricity on the current i is affected. It has been eliminated. Further, 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 V1 of the measurement object 4 is measured.

  Thus, in this voltage measuring apparatus 1, each of the connection points A, B, and D of the capacitance changing function body 13 as a portion in a floating state with respect to the reference potential in the probe unit 2 and the case 11 as the reference potential The resistors 51, 52, 53 are connected to each other, and the resistor 54 is connected between the connection point E of the detection electrode 12 and the capacitor 20 and the case 11. And a non-floating state by connecting to a reference potential via a series circuit formed by any one of the voltage generation circuit 25 and the output impedance Z1 of the voltage generation circuit 25. As a result, the voltage measuring apparatus 1 as a whole is affected by static electricity. It can be configured to be difficult to receive. For this reason, as a result of reducing the fluctuation due to static electricity of the voltage of each part in the voltage detection apparatus 1, the fluctuation due to static electricity of the voltage of the detection system can also be reduced, and the measurement (detection) of the voltage V1 of the measuring object 4 Sufficient measurement accuracy (detection accuracy) can be ensured.

  In particular, according to the voltage measuring apparatus 1, the resistor 54 is connected between the detection electrode 12 and the case 11 as an example between the detection electrode 12 and the reference potential, so that the detection system may be in a floating state. Since the detection electrode 12 having the highest value can be brought into a non-floating state, the influence of static electricity on the detection system can be directly reduced (the voltage stability of the detection system can be directly increased). The measurement accuracy for the voltage measurement of the measurement object 4 can be reliably improved. Further, according to the voltage measuring apparatus 1, since the resistors 52 and 53 are connected between the variable capacitance circuit 19 and the reference potential, the variable capacitance circuit 19 (specifically, the detection system is likely to be in a floating state). The connection points B and D) of the capacitance change function body 13 can be brought into a non-floating state. For this reason, it is possible to reliably improve the measurement accuracy for the voltage measurement of the measurement object 4 in the same manner as when the resistor 54 is connected.

  Further, according to the voltage measuring apparatus 1, the capacitor 20 connected in series between the detection electrode 12 and the variable capacitance circuit 19 is also connected to the terminal on the variable capacitance circuit 19 side (the connection point A of the capacitance changing function body 13. ) And the case 11, the terminal on the variable capacitance circuit 19 side of the capacitor 20 that may be in a floating state in the detection system can be brought into a non-floating state. As a result, the voltage stability of the measuring object 4 can be measured while protecting the variable capacitance circuit 19 from voltage application due to contact between the measuring object 4 and the detection electrode 12. Measurement accuracy can be further improved.

  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. Even in the configuration employing the capacitance changing function body 13A, by connecting the resistors 51 to 54 as described above, a portion that may be in a floating state can be brought into a non-floating state. The measurement accuracy of voltage measurement can be improved. In the capacity change function body 13A shown in FIG. 5, when the capacitors 62 and 63 are replaced with resistors (or coils), the connection points B and D in the capacity change function body 13A are connected to the resistors (or coils) and It is connected to the case 11 via the current detector 15 in a direct current manner. For this reason, in this configuration, the arrangement of the resistors 52 and 53 can be omitted.

  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 the capacitance changing function body 13A, by connecting the resistors 51 to 54 as described above, a portion that may be in a floating state can be brought into a non-floating state. The measurement accuracy for voltage measurement can be improved.

  Further, in the voltage measuring apparatus 1 shown in FIG. 1, the configuration using the capacitor 20 is adopted, but a configuration not using the capacitor 20 can also be adopted. In this configuration, since the connection point A of the capacitance change function body 13 is directly connected to the detection electrode 12, the arrangement of one of the resistors 51 and 54 can be omitted. Further, in the voltage measuring device 1, since the current detector 15 is configured by a resistor, the end portion on the case 11 side of each resistor 51, 52, 53, 54 is connected to the connection point C of the capacitance changing function body 13. May be.

  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 In this configuration, the arrangement of the current detector 15 can be omitted. Also in this configuration, in the same manner as the voltage measuring apparatus 1 described above, this resistance can be obtained by connecting a resistor between a portion that may be in a floating state in the probe unit 2 and the case 11 as a reference potential. As a result of connecting the part that may be in a floating state to a reference potential via a series circuit (resistor in the present invention) of the output impedance Z1 of the voltage generation circuit 25, the measurement object 4 can be brought into a non-floating state. The measurement accuracy for the voltage measurement can be improved.

  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.

  The invention of the present application is not limited to the voltage measuring device 1 provided with each capacitance changing function body 13 described above, and can be applied to all voltage detecting devices including a probe unit 2 that may be in a floating state. Of course.

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 C3 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Voltage measuring device 3 Main body unit 4 Measurement object 11 Case 12 Detection electrode 13, 13A, 13B 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 51-54 Resistance CNT control part E11-E14 1st electric element E22, E23 2nd electric element E33, E34 3rd electric element i Current V1 Voltage of measuring object V4 Feedback voltage ( Reference potential)
Z1 output impedance

Claims (5)

A voltage detection device configured to be able to detect a voltage of a measurement object based on a reference potential,
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 voltage detection apparatus comprising: a portion that is in a floating state with respect to the reference potential; and a resistor connected between the reference potential.   The voltage detection device according to claim 1, wherein the resistor is connected between the detection electrode and the reference potential.   The voltage detection device according to claim 1, wherein the resistor is connected between the variable capacitance circuit and the reference potential. A capacitor connected in series between the detection electrode and the variable capacitance circuit;
The voltage detection device according to claim 1, wherein the resistor is connected between a terminal on the variable capacitance circuit side of the capacitor and 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;
5. The voltage according to claim 1, further comprising: 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. 6. Detection circuit.

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