JP2007163414A - Variable capacitance circuit, voltage measuring apparatus, and electric power measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable variable capacitance circuit having a high-speed operating frequency. <P>SOLUTION: The variable capacitance circuit is provided with: a capacitance-changing function body 13 and a driving circuit 14. In the capacitance-changing function body 13, a first constituent unit 31; a second constituent unit 32; a third constituent unit 33; and a fourth constituent unit 34 each include a diode and are connected into a ring sequentially in this order, and the product of the impedances of the first and third constituent units 31 and 33 and the product of the impedances of the second and fourth constituent units 32 and 34 are specified as to be the same or approximately the same. The driving circuit 14 comprises both a transformer 14a for inducing an AC component in a secondary winding 14c and a DC current power source 14b for generating a DC voltage and applies a drive signal S2 between a point B of connection between the first and second constituent units 31 and 32 and a point D of connection between the third and fourth constituent units 33 and 34. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a variable capacitance circuit that can change its capacitance at high speed, a voltage measurement device that includes this variable capacitance circuit and that can measure the voltage of a measurement object in a non-contact manner, and power that uses this voltage measurement device. The present invention relates to a measuring device.

  As this type of voltage measuring device, various voltage measuring devices disclosed in Japanese Patent Laid-Open Nos. 4-305171 and 7-244103 are known.

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

On the other hand, in the conventional technique disclosed in Japanese Patent Application Laid-Open No. 7-244103, the disclosed voltage measuring device (distance compensated surface potential meter) has an input hole among electric lines of force emitted from the surface of the measurement object (sample). Due to the lines of electric force passing through the detection electrode (fixed electrode), the surface of the detection electrode has a charge proportional to the potential of the measurement object and proportional to the capacitance between the detection electrode and the measurement object. Will occur. In addition, the conductor sector mechanically operates to repeatedly shield and open the electric lines of force that reach the detection electrode through the input hole. As a result, the charge of the detection electrode is repeatedly generated and extinguished, a current proportional to the rate of change flows through the load resistance, and an alternating voltage is generated at the load resistance. The voltage measuring device disclosed in Japanese Patent Application Laid-Open No. 7-244103 is different from the voltage measuring device described in Japanese Patent Application Laid-Open No. 4-305171 in the configuration for generating the AC voltage. This is basically the same as the voltage measuring device disclosed in Japanese Patent Laid-Open No. 4-305171, and is based on the alternating voltage generated in the load resistance between the probe case (equivalent to the case of the probe unit) and the measurement object. By reducing the potential difference, the potential of the measurement object is measured in the same manner as in the voltage measuring apparatus disclosed in Japanese Patent Laid-Open No. 4-305171.
Japanese Patent Laid-Open No. 4-305171 (page 2, FIG. 6) JP 7-244103 A (2nd page, FIG. 9)

  However, each of the voltage measuring devices has the following problems. That is, in the voltage measuring device disclosed in Japanese Patent Laid-Open No. 4-305171, the detection electrode is vibrated by the vibrating body. In the voltage measuring device disclosed in Japanese Patent Laid-Open No. 7-244103, the conductor sector is mechanically operated. Therefore, both voltage measuring devices have a problem that it is difficult to increase the operating frequency and it is difficult to improve the reliability due to the mechanically movable configuration. is doing.

  The present invention has been made to solve the above problems, and has as its main object to provide a variable capacitance circuit, a voltage measuring device, and a power measuring device that have a high operating frequency and high reliability.

  In order to achieve the above object, the variable capacitance circuit according to claim 1 includes a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit each including at least one variable capacitive element. The product of each impedance of the first structural unit and the third structural unit is the same as the product of the impedances of the second structural unit and the fourth structural unit. Or having substantially the same capacity changing function body, a transformer for inducing an AC component in the secondary winding and a DC power source for generating a DC voltage, and the secondary winding and the DC power source of the transformer Is connected in series between the connection point of the first structural unit and the second structural unit and the connection point of the third structural unit and the fourth structural unit, and includes the AC component DC By applying pressure to the capacitance changing structure and a drive circuit for changing the capacitance of the capacitance changing structure.

  According to a second aspect of the present invention, in the variable capacitance circuit according to the first aspect, the variable capacitance element includes a P-type semiconductor and an N-type semiconductor that are joined to each other.

  The variable capacitance circuit according to claim 3 is the variable capacitance circuit according to claim 2, wherein the variable capacitance element includes a diode formed of the P-type semiconductor and the N-type semiconductor. The respective diodes included in the structural unit and the fourth structural unit are arranged in the same direction in the annular circuit composed of the four structural units, and the second structural unit and the third structural unit are arranged. Each of the diodes included in the structural unit is disposed in the annular circuit in a direction opposite to the direction of the diodes in the first and fourth structural units.

  According to a fourth aspect of the present invention, there is provided the variable capacitance circuit according to the second aspect, wherein the P-type semiconductor, the N-type semiconductor, and the second structural unit included in the first structural unit are included. A set of the P-type semiconductor and the N-type semiconductor included, and the P-type semiconductor, the N-type semiconductor, and the fourth structural unit included in the third structural unit At least one set of the P-type semiconductor and the N-type semiconductor is composed of one transistor.

  The voltage measuring device according to claim 5 is a voltage measuring device configured to be able to measure the voltage of the measurement object, and the detection electrode capable of facing the measurement object, and any one of claims 1 to 4 The variable capacitance circuit includes a connection point of the first structural unit and the fourth structural unit located on the detection electrode side, and the second structural unit and the variable structural circuit. The connection point of the third structural unit is disposed between the detection electrode and the reference potential so that the connection point is located on the reference potential side.

  According to a sixth aspect of the present invention, there is provided the voltage measuring device according to the fifth aspect, further comprising: a voltage generating circuit that generates the reference potential; and a control unit, wherein the variable capacitance circuit includes the variable capacitance circuit. When the capacitance is changed, the voltage of the reference potential is changed with respect to the voltage generation circuit.

  The voltage measuring device according to claim 7 is the voltage measuring device according to claim 6, wherein the control unit is configured to change the detection electrode and the reference potential via the variable capacitance circuit when the capacitance changes. Or the reference potential with respect to the voltage generation circuit so that the voltage generated between the end on the detection electrode side and the end on the reference potential side in the variable capacitance circuit decreases. Vary the voltage.

  The voltage measuring device according to claim 8 is the voltage measuring device according to claim 7, further comprising an impedance element arranged in series with the variable capacitance circuit between the detection electrode and the reference potential. The control unit changes the voltage of the reference potential for the voltage generation circuit so that the voltage generated in the impedance element decreases when the current flows through the impedance element.

  The voltage measurement device according to claim 9 is the voltage measurement device according to claim 7, further comprising a resonance circuit disposed in series with the variable capacitance circuit between the detection electrode and the reference potential. The control unit changes the voltage of the reference potential for the voltage generation circuit so that the voltage generated in the resonance circuit decreases when the current flows through the resonance circuit.

  The voltage measuring device according to claim 10 is the voltage measuring device according to any one of claims 7 to 9, wherein the control unit is configured such that the current value, or the end on the detection electrode side and the reference potential are set. An A / D conversion circuit for inputting a detection signal whose voltage value changes in accordance with the value of the voltage generated between the digital signal and the digital signal, and detecting the detection signal based on the digital data The voltage of the reference potential is changed with respect to the voltage generation circuit so that the voltage value decreases.

  The power measurement device according to claim 11 is a current measurement device that measures a current flowing through a measurement object, and a voltage measurement according to any one of claims 5 to 10 that measures a voltage of the measurement object. And measuring power based on the current measured by the current measuring device and the voltage measured by the voltage measuring device.

  The variable capacitance circuit according to claim 1 includes a configuration in which the first to fourth structural units including the variable capacitance elements are connected in a ring shape to form the capacitance changing function body, thereby mechanically movable. Compared with the variable capacitance circuit, it is possible to change the capacitance at a high frequency of several hundred kHz to several MHz (the operation frequency can be increased), and it is possible to realize a highly reliable variable capacitance circuit. Further, by configuring the product of the impedances of the first structural unit and the third structural unit and the product of the impedances of the second structural unit and the fourth structural unit to be the same or substantially the same. In order for the capacitance changing function body to satisfy the equilibrium condition as the bridge circuit, the connection point between the first structural unit and the second structural unit, the connection point between the third structural unit and the fourth structural unit, When a DC voltage including an AC component for driving is applied between the first structural unit and the fourth structural unit, the connection point between the second structural unit and the third structural unit. The voltage component of this alternating current component can be prevented from being generated between For this reason, it is possible to eliminate the influence of the AC component included in the driving DC voltage on the AC current generated in the variable capacitance circuit or the voltage across the variable capacitance circuit when the capacitance changes. In addition, since the drive circuit has a transformer that induces an AC component in the secondary winding and a DC power source that generates a DC voltage, the capacitance change function body includes the AC component in a simple and inexpensive configuration. A DC voltage can be applied.

  According to the variable capacitance circuit of the second aspect, the variable capacitance circuit can be greatly reduced in size by having the variable capacitance element having the P-type semiconductor and the N-type semiconductor joined to each other. .

  According to the variable capacitance circuit of the third aspect, the variable capacitance circuit can be configured easily and inexpensively by configuring the variable capacitance element with a diode. In addition, the direction of each diode included in the first structural unit and the fourth structural unit is arranged in the same direction in the annular circuit composed of four structural units, and the second structural unit By disposing each diode included in the structural unit and the third structural unit in the annular circuit so that the directions of the diodes in the first and fourth structural units are opposite to each other, All the diodes can always be reverse-biased by the applied DC voltage. Accordingly, direct current is prevented from flowing from the connection point between the first structural unit and the fourth structural unit to the connection point between the second structural unit and the third structural unit via each structural unit. be able to.

  According to the variable capacitance circuit of the fourth aspect, the combination of the variable capacitance element included in the first structural unit and the variable capacitance element included in the second structural unit, and the third configuration By configuring at least one of the combination of the variable capacitance element included in the unit and the variable capacitance element included in the fourth structural unit with one transistor, a variable capacitance circuit can be configured more easily. be able to. Further, in the same manner as the above-described variable capacitance circuit in which the variable capacitance element is configured by a diode, the second configuration unit is connected through the respective configuration units from the connection point between the first configuration unit and the fourth configuration unit. It is possible to prevent a direct current from flowing to the connection point with the third structural unit.

  According to the voltage measuring device of the fifth aspect, the detection electrode capable of facing the measurement object and the variable capacitance circuit are provided, and the connection point of the first structural unit and the fourth structural unit is detected. The variable capacitance circuit is disposed between the detection electrode and the reference potential by positioning the connection point of the second structural unit and the third structural unit on the reference potential side by being located on the electrode side and changing the capacitance. A configuration using a variable capacitance circuit including a configuration that is mechanically movable by changing the capacitance of the functional body and measuring the voltage of the measurement target body using the capacitance changing operation of the capacitance changing functional body. In comparison, since the variable capacitance circuit can change the capacitance at a high frequency and has high reliability, the voltage of the measurement object can be measured in a short time, and the voltage measuring device itself Can improve the reliability of

  According to the voltage measuring device of the sixth aspect, the voltage measuring circuit for generating the reference potential and the control unit are provided, and the variable capacitance circuit (specifically, the capacitance changing function body) changes the capacitance. When the control unit changes the reference potential voltage with respect to the voltage generation circuit, the detected reference voltage is detected via the variable capacitance circuit when it matches the voltage of the measurement object. The measurement object using the fact that the current flowing between the electrode and the reference potential, or the voltage generated between the end on the detection electrode side and the end on the reference potential side in the variable capacitance circuit becomes almost zero. Can be measured with high accuracy.

  According to the voltage measuring device of the seventh aspect, the current flowing between the detection electrode and the reference potential through the variable capacitance circuit or the detection in the variable capacitance circuit when the capacitance in the variable capacitance circuit changes. The control unit changes the voltage of the reference potential with respect to the voltage generation circuit so that the voltage generated between the electrode-side end and the reference potential-side end is reduced, thereby ensuring a short time and surely. Since the voltage of the reference potential can be matched with the voltage of the measurement object, the voltage of the measurement object can be reliably measured in a short time while maintaining high measurement accuracy.

  According to the voltage measuring apparatus of the eighth aspect, the impedance element is arranged in series with the variable capacitance circuit between the detection electrode and the reference potential, and when the current flows through the impedance element, The value of the voltage generated in the impedance element when the current flows by changing the impedance value of the impedance element by changing the reference potential voltage with respect to the voltage generation circuit so that the generated voltage decreases. Can be changed arbitrarily. For this reason, the voltage of the measurement object can be accurately measured over a wide voltage range from a low voltage to a high voltage.

  In the voltage measuring device according to claim 9, a resonance circuit is arranged in series with the variable capacitance circuit between the detection electrode and the reference potential, and is generated in the resonance circuit when a current flows through the resonance circuit. The control unit changes the voltage of the reference potential with respect to the voltage generation circuit so that the voltage decreases. Therefore, according to this configuration, it is possible to arbitrarily change the value of the voltage generated in the resonance circuit when a current flows by changing the impedance value at the time of resonance of the resonance circuit. The voltage of the measurement object can be measured over a wide voltage range. In addition, by changing the capacitance of the variable capacitance circuit at the resonance frequency of the resonance circuit, the current flowing through the resonance circuit can be detected as a larger voltage. As a result, noise resistance can be improved, so that the voltage of the measurement object can be measured with few malfunctions.

  According to the voltage measuring device of claim 10, the detection signal whose voltage value changes in accordance with the value of the current flowing through the variable capacitance circuit or the value of the voltage generated in the variable capacitance circuit is converted into digital data. An A / D conversion circuit that changes the reference potential voltage with respect to the voltage generation circuit so that the voltage value of the detection signal decreases based on the digital data. The control unit can be easily configured by a digital circuit using a digital signal processor.

  The power measuring device according to claim 11 is provided with a current measuring device for measuring a current flowing through the measuring object and the voltage measuring device for measuring a voltage of the measuring object, and is measured by the current measuring device. Based on the measured current and the voltage measured by the voltage measuring device, for example, the power supplied to the measurement object is measured. Therefore, according to this power measuring device, the reliability of the power measuring device itself can be sufficiently improved by providing the highly reliable voltage measuring device.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, the best mode of a variable capacitance circuit, a voltage measuring device, and a power measuring device according to the invention will be described with reference to the accompanying drawings.

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

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

  As illustrated in FIG. 1, the variable capacitance circuit 19 includes one capacitance change function body 13 and one drive circuit 14. The capacity 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 that are connected in a ring shape in this order to form a so-called bridge circuit (in the present invention). (Circular circuit). In this case, each of the structural units 31 to 34 includes at least one variable capacitance element (a diode as an example) configured to have a P-type semiconductor and an N-type semiconductor joined to each other. Specifically, as shown in FIG. 2, the first structural unit 31 of the capacitance change function body 13 includes a single diode (variable capacitance diode as an example, also referred to as a varicap or a varactor diode) 41. ing. Similarly, the second structural unit 32, the third structural unit 33, and the fourth structural unit 34 are each provided with one diode 42, 43, 44 (all of which are variable capacitance diodes). . Further, the diodes 41 and 44 included in the first and fourth structural units 31 and 34 are arranged in a predetermined direction (the same direction as shown by an arrow E in FIG. 2) in the annular circuit. Has been. The diodes 42 and 43 included in the second and third structural units 32 and 33 are opposite to the directions of the diodes 41 and 44 in the annular circuit (the direction indicated by the arrow F in FIG. 2). It is arranged by. In this example, the directions of the diodes 41 and 44 and the diodes 42 and 43 are respectively defined so that a direct current flows from the connection point B to the connection point D through each structural unit. In addition, variable capacitance diodes having the same or substantially the same characteristics are used for each of the diodes 41 to 44, and the product of the impedances of the first structural unit 31 and the third structural unit 33 and the second structural unit 32. And the product of each impedance of the fourth structural unit 34 is set to be the same or substantially the same (a state that is different within a range of about several percent as an example).

  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, even if it is the structure (refer FIG. 3) which replaced all the variable capacity | capacitance diodes 41-44 shown in FIG. 2 with the general diodes 51-54, the capacity | capacitance change function body 13 can be comprised.

  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 is electrically insulated from the drive signal S1 and the drive signal S1. Is converted to a drive signal S2 (DC voltage in the present invention) including an AC component of the same frequency f1 and output (applied) to the capacitance changing function body 13. Specifically, in this example, the drive circuit 14 includes a transformer 14a and a DC power supply 14b as shown in FIG. The transformer 14a and the DC power supply 14b are configured in a series circuit in which the negative electrode of the DC power supply 14b is connected to one end (the upper end in the figure) of the secondary winding 14c of the transformer 14a, and the other end of the secondary winding 14c. (The lower end in the figure) is connected to the connection point B of the capacity changing function body 13, and the positive electrode of the DC power supply 14b is connected to the connection point D. The drive circuit 14 thus configured converts the input drive signal S1 into an AC component (AC signal) electrically insulated from the drive signal S1 by the transformer 14a with low distortion, and converts the AC component to a DC power source. A drive signal S2 as a DC voltage is generated by being superimposed on the DC voltage of 14b and applied between the connection points B and D of the capacitance change function body 13. 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 in a state of being connected in series with the capacitance change function body 13, and the current i (physical quantity) flowing through the capacitance change function body 13. ) 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.

  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, and a voltmeter 26. The oscillation circuit 21 generates a drive signal S1 having a constant period T1 (a constant frequency) and outputs it to the probe unit 2 and 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. The amplifying circuit 22 amplifies the detection signal S3 input from the probe unit 2 to a preset voltage level and outputs it as a detection signal S4. In this example, the capacitance modulation frequency of the capacitance C1 of the capacitance change function body 13 is the same as the frequency of the AC component included in the drive signal S2, as will be described later. Therefore, the frequency of the current i generated by the change in the capacitance C1 is the same as the frequency of the drive signal S1, and the frequency of the detection signal S3 generated by the preamplifier 16 is also the same as the frequency of the drive signal S1. Therefore, in this example, the synchronous detection circuit 23 is configured to generate the pulse signal S5 by synchronously detecting the detection signal S4 with the drive signal S1. In this case, the amplitude of the pulse signal S5 changes in proportion to the value of the current i flowing through the capacitance change function body 13, and the polarity changes according to the direction of the current i flowing through the capacitance change function body 13. 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. The amplifier circuit 22, the synchronous detection circuit 23, and the 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 V1 of the measuring object 4 using the voltage measuring device 1. In order to facilitate understanding of the invention, the voltage V1 is assumed to be a positive constant voltage as an example. However, when the voltage V1 is a negative constant voltage, the polarity of the corresponding signal or voltage is reversed. The measurement is performed in the same manner as in the case of a positive constant voltage except that. Also, when the voltage V1 is alternating current, in principle, the measurement is performed in the same manner as when the voltage is a positive constant voltage or a negative constant voltage.

  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). .

  Next, in the activated state of the voltage measuring device 1, in the main unit 3, the oscillation circuit 21 starts generating the drive signal S 1 and outputs the drive signal S 1 to the probe unit 2 and the synchronous detection circuit 23. In the probe unit 2, the drive circuit 14 converts the input drive signal S1 into a drive signal S2 in which an alternating current component having the same frequency f1 as the drive signal S1 is superimposed on a direct current voltage of the direct current power supply 14b to convert the capacitance change function body. The connection point D is applied (output) between the 13 connection points B and D so that the connection point D is always at a positive potential (high potential).

  In the capacitance change function body 13, the drive signal S2 applied between the connection points B and D is divided to be the first structural unit 31, the second structural unit 32, the third structural unit 33, and the fourth structural unit. Applied to each of the structural units 34. In this case, each of the diodes 41 to 44 constituting each of the structural units 31 to 34 functions as a capacitor to which a reverse voltage is always applied (reversely biased). Further, since the voltage value of the applied voltage continuously changes in the cycle of the AC component of the drive signal S2 (same cycle T1 as the drive signal S1), each of the diodes 41 to 44 functioning as capacitors is Is continuously changed in synchronization with the AC component of the drive signal S2 in the cycle T1 of the AC component of the drive signal S2. Therefore, the capacitance changing function body 13 continuously has the capacitance C1 (capacitance between the connection points A and B) in synchronization with the AC component of the drive signal S2 in the cycle T1 of the AC component of the drive signal S2. Is changing. Further, in this way, in the capacitance change function body 13, the diodes 41 and 42 constituting the constituent units 31 and 34 and the diodes 42 and 43 constituting the constituent units 32 and 33 are respectively reverse-biased so Therefore, all the structural units 31 to 34 function so as to allow passage of alternating current and prevent passage of direct current. For this reason, in the probe unit 2, the detection electrode 12 and the case 11 are maintained so as not to be short-circuited in a direct current via the capacitance change function body 13 (so that a direct current does not flow through the capacity change function body 13). Yes.

  Further, in the capacitance change function body 13, as described above, the product of the impedances of the first structural unit 31 and the third structural unit 33, and the impedances of the second structural unit 32 and the fourth structural unit 34, respectively. Are set to be the same or almost the same. Accordingly, since the capacitance changing function body 13 which is also a bridge circuit satisfies the equilibrium condition as the bridge circuit, the voltage component (the voltage signal having the same frequency f1 as the drive signal S1) for the AC component of the drive signal S2 is different. The electrostatic capacity C1 is changed with the period T1 in a state in which hardly occurs between the connection points A and C. Note that until the feedback voltage V4 coincides with the voltage V1, that is, while a potential difference is generated between the feedback voltage V4 and the voltage V1, between the connection points A and C of the capacitance change function body 13, A voltage is generated by dividing the potential difference (V1-V4) between the measurement object 4 and the case 11 by the capacitance C0 and the capacitance C1.

  Further, the integrator 24 outputs a DC voltage V3 of zero volts immediately after the operation of the voltage measuring device 1, so that the voltage generation circuit 25 has a predetermined feedback voltage V4 (for example, a voltage lower than the voltage V1). And is 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 T1 based on the periodic change in the cycle C1 of the capacitance C1. A current i flows through the capacitance changing function body 13 while changing the current value at the cycle T1. 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 a positive constant voltage, and the feedback voltage V4 starts from zero volts. Therefore, 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 T1. 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 frequency of the detection signal S3 is the same as the frequency f1 of the current i.

  In the control unit CNT of the main unit 3, the amplifier circuit 22 amplifies the detection signal S 3 to generate a detection signal S 4 and outputs it 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 drive signal S1, 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 voltage value of the feedback voltage V4 generated by the voltage generation circuit 25 gradually increases as shown in FIG. As a result, in the feedback loop composed of the current detector 15, the preamplifier 16, the amplifier circuit 22, the synchronous detection circuit 23, the integrator 24, and the voltage generation circuit 25, a potential difference ( Negative feedback is performed so that V1-V4) gradually decreases (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. The rise of the voltage V3 is also stopped and maintained at a constant voltage. For this reason, the feedback voltage V4 output from the voltage generation circuit 25 stops increasing, and the feedback voltage V4 is maintained at a constant voltage as shown in FIG. Therefore, when the voltage value (feedback voltage V4) displayed on the voltmeter 26 is continuously observed and the increase in the voltage value stops and becomes constant (that is, when the current i becomes zero ampere). ), The voltage value (feedback voltage V4) displayed on the voltmeter 26 at that time is measured as the voltage V1 of the measuring object 4. Thus, the voltage V1 of the measurement object 4 is completed.

  As described above, in this voltage measuring apparatus 1, the first structural unit 31 including each one of the variable capacitance elements (diodes as an example) each having a P-type semiconductor and an N-type semiconductor joined to each other, A variable capacitance circuit 19 is configured including the capacitance changing function body 13 configured by annularly connecting the second structural unit 32, the third structural unit 33, and the fourth structural unit 34 in this order. Therefore, according to the variable capacitance circuit 19, since there is no mechanically movable configuration, it is possible to change the capacitance at a high frequency of several hundred kHz to several MHz (the operating frequency can be increased). In addition, a highly reliable variable capacitance circuit can be realized, and the variable capacitance circuit can be greatly reduced in size. Further, in the voltage measuring apparatus 1, a diode is used as a variable capacitance element, and each of the diodes 41 and 44 included in the first structural unit 31 and the fourth structural unit 34 is arranged in the same direction in the annular circuit. The diodes 42 and 43 included in the second structural unit 32 and the third structural unit 33 are arranged in opposite directions to the directions of the diodes 41 and 44 in the annular circuit. Thus, the capacity changing function body 13 is configured. Further, the positive electrode of the DC power supply 14b in the drive circuit 14 is connected to the connection point D of the capacity changing function body 13, and the negative electrode of the DC power supply 14b is connected to the connection point B through the secondary winding 14c of the transformer 14a. . For this reason, by applying a DC voltage from the drive circuit 14 to each of the diodes 41 to 44, each of the diodes 41 to 44 can be constantly reverse-biased. Therefore, according to the variable capacitance circuit 19 including the capacitance change function body 13, each of the diodes 41 to 44 can be reliably operated as a variable capacitance element. Further, from the connection point A between the first structural unit 31 and the fourth structural unit 34 to the connection point B between the second structural unit 32 and the third structural unit 33 via the respective structural units 31 to 34. The direct current can be prevented from flowing, and the detection electrode 12 and the case 11 can be prevented from being short-circuited via the variable capacitance circuit 19. In addition, since the drive circuit 14 is configured by including the transformer 14a and the DC power supply 14b, a DC voltage (drive signal S2) including an AC component is applied to the capacitance changing function body 13 with a simple and inexpensive configuration. Can do.

  Further, in the voltage measuring apparatus 1 using the variable capacitance circuit 19, a constant (fixed) electrostatic capacitance is provided between the measurement object 4 and the detection electrode 12 by making the detection electrode 12 face the measurement object 4. C0 is formed, and in this state, the capacitance C1 of the capacitance changing function body 13 is periodically changed, and the voltage V1 of the measuring object 4 is changed by using the capacitance changing operation of the capacitance changing function body 13. Measuring. Therefore, according to the voltage measuring device 1, compared with the configuration using the variable capacitance circuit including the mechanically movable configuration, the reliability of the device itself is sufficiently improved while the number of the feedback voltage V4 is several. As a result of being able to control at a high frequency such as hundred kHz to several MHz, the voltage V1 of the measuring object 4 can be measured in a short time. Furthermore, according to the voltage measuring apparatus 1, the voltage V1 of the measuring object 4 can be measured in a state where the detection electrode 12 is disposed on the surface of the case 11 and the variable capacitance circuit 19 is disposed inside the case 11. In addition, it is not necessary to provide a hole in the case 11 for making the variable capacitance circuit 19 directly face the measurement object 4. As a result, it is possible to reliably avoid a situation in which foreign matter is erroneously inserted into the case 11 through this hole, and damage to the components in the case 11 due to this erroneous insertion. Reliability can be further improved.

  Further, in the voltage measuring apparatus 1, the control unit CNT changes the voltage of the feedback voltage V4 with respect to the voltage generation circuit 25 when the capacitance changing function body 13 periodically changes the capacitance C1. . Therefore, according to the voltage measuring apparatus 1, the current i is zero ampere while detecting the current i generated (flowing) in the capacity change function body 13 when the capacity change function body 13 periodically changes the capacity. By measuring this feedback voltage V4 at the time as the voltage V1 of the measuring object 4, the voltage V1 of the measuring object 4 can be measured with high accuracy. Furthermore, according to the voltage measuring apparatus 1, the control unit CNT changes the feedback voltage V4 to the voltage generation circuit 25 so that the detected current i is decreased, whereby the feedback voltage V4 is measured. 4 can be made to coincide with the voltage V1 of 4 in a short time and reliably. As a result, the voltage V1 of the measuring object 4 can be measured reliably in a short time while maintaining high measurement accuracy. In particular, according to the voltage measuring apparatus 1, the capacitance C2 between the measurement object 4 and the case 11 can be changed at a high frequency as described above, so that the current detector 15 to the voltage generation circuit 25 are changed. As a result of increasing the response speed of the feedback loop, the voltage V1 of the measuring object 4 can be measured in a shorter time. For this reason, according to this voltage measuring apparatus 1, even when the voltage V1 of the measuring object 4 fluctuates with time or when the voltage V1 of the measuring object 4 is an alternating voltage that periodically changes, the voltage V1 can be accurately measured.

  Also, according to the variable capacitance circuit 19, as described above, the product of the impedances of the first structural unit 31 and the third structural unit 33, and the second structural unit 32 and the fourth structural unit 34, respectively. By configuring the capacitance changing function body 13 so that the product of impedance is the same or substantially the same, the capacitance changing function body 13 configured as a bridge circuit (annular circuit) by connecting each of the structural units 31 to 34 in a ring shape. Satisfies the equilibrium condition as a bridge circuit, when the drive signal S2 is applied between the connection points B and D, the voltage component of the AC component of the drive signal S2 (the voltage signal having the same frequency f1 as the drive signal S1) ) Can hardly be generated between the connection points A and C, and the capacitance C1 can be changed with the period T1. Therefore, according to the voltage measuring apparatus 1 using the variable capacitance circuit 19, the influence of the drive signal S2 (the influence of the AC component of the drive signal S2) on the current i generated in the capacitance change function body 13 when the capacitance changes. As a result, the current i can be detected more accurately by the preamplifier 16, and the voltage V1 of the measurement object 4 can be measured more accurately.

  In addition, according to the voltage measuring apparatus 1, the current detector 15 composed of an impedance element is connected in series with the variable capacitance circuit 19 (specifically, the capacitance changing function body 13) between the detection electrode 12 and the case 11. The control unit CNT changes the feedback voltage V4 (the voltage of the case 11) to the voltage generation circuit 25 so that the voltage V2 generated when the current i flows through the current detector 15 decreases. By adopting the configuration, the value of the voltage V2 generated when the current i flows can be arbitrarily changed by changing the impedance value of the impedance element. For this reason, the voltage V1 of the measuring object 4 can be measured over a wide voltage range from a low voltage to a high voltage.

  In addition, this invention is not limited to said structure. For example, in the voltage measuring apparatus 1 described above, the feedback voltage V4 is controlled by I (proportional) control, but at least one of an integration circuit and a differentiation circuit (both not shown) is further included in the feedback loop. In addition, the feedback voltage V4 can be controlled by any one of PI (proportional / integral) control, PD (proportional / differential) control, and PID (proportional / integral / differential) control. By adopting this PID control, the followability to the voltage V1 can be improved, so that the voltage V1 can be measured with high accuracy, particularly when the voltage V1 of the measurement object 4 changes.

  Further, in the voltage measuring apparatus 1 described above, each of the structural units 31 to 34 is configured by one diode, but the product of the impedances of the first structural unit 31 and the third structural unit 33, and the second As long as the products of the impedances of the structural unit 32 and the fourth structural unit 34 are the same or substantially the same, two or more diodes are connected in series or in parallel in the forward direction (with the same orientation) to form each structural unit. 31-34 can also be comprised.

  Further, in the capacitance change function body 13 shown in FIG. 3, each of the structural units 31 to 34 is configured by a diode, but the pair of diodes 51 and 52 that configure each of the structural units 31 and 32 has anode terminals that are connected to each other. By being connected at the connection point B, they are connected in series in opposite directions in the annular circuit. In other words, the series circuit composed of the structural units 31 and 32 is configured by arranging a P-type semiconductor and an N-type semiconductor in the form of NPPN. The pair of diodes 53 and 54 constituting each of the structural units 33 and 34 are connected in series in opposite directions in the annular circuit by connecting the cathode terminals at the connection point D. That is, the series circuit composed of the respective structural units 33 and 34 is configured by arranging a P-type semiconductor and an N-type semiconductor as PNNP. For this reason, in the capacitance change function body 13 shown in FIG. 3, the pair of diodes 51 and 52 constituting each of the structural units 31 and 32 is replaced with one NPN-type bipolar transistor TR1, and the pair of the structural units 33 and 34. By replacing the diodes 53 and 54 with one PNP-type bipolar transistor TR2, a capacitance change function body 13A substantially equivalent to the capacity change function body 13 can be formed as shown in FIG. In this capacitance change function body 13A, the transistors TR1 and TR2 are connected to each other at their collector terminals and emitter terminals (or from collector terminals to each other and emitter terminals are connected to each other). Points A and C. The base terminal of the transistor TR1 is the connection point B, and the base terminal of the transistor TR2 is the connection point D. Moreover, although the example which uses a bipolar transistor as a transistor was demonstrated, it replaced with a NPN type bipolar transistor, and may use the same type MOSFET (field effect type transistor), or it replaced with a PNP type bipolar transistor, and the same type. Of course, a MOSFET (field effect transistor) may be used. As described above, by using the transistors TR1 and TR2 to form a pair of adjacent structural units 31 and 32 and another pair of adjacent structural units 33 and 34, a capacitance changing function body having a simpler configuration. 13A can be realized.

  Further, as shown in FIG. 6, the probe unit 2A can be configured without providing the current detector 15. In this probe unit 2A, the preamplifier 16 uses the voltage V5 between both ends of the capacitance change function bodies 13 and 13A (they are collectively referred to as the capacitance change function body 13 unless otherwise distinguished), that is, the detection electrode in the capacitance change function body 13. A voltage V5 generated between the end on the 12 side (connection point A) and the end on the case 11 side (connection point C) in the capacitance change function body 13 is detected and output as a detection signal S3. Therefore, in the voltage measuring apparatus 1A using the probe unit 2A, the control unit CNT controls the voltage generation circuit 25 based on the detection signal S3 that changes in proportion to the voltage V5 between both ends, and the voltage of the measurement object 4 is detected. V1 is measured. In this case, one input terminal of the pair of input terminals in the preamplifier 16 is connected to the end portion (connection point A) on the detection electrode 12 side in the capacitance change function body 13 via the capacitor 17 as shown in FIG. The other input terminal is connected to the end portion (connection point C) on the case 11 side of the capacitance change function body 13. Since the voltage measuring device 1A is the same as the voltage measuring device 1 except for this configuration, the same components as those of the voltage measuring device 1 are denoted by the same reference numerals in FIG. A duplicate description is omitted. Also in this voltage measuring device 1A, by using the variable capacitance circuit 19 including the capacitance changing function body 13, the feedback loop response of the current detector 15 to the voltage generating circuit 25 is the same as in the voltage measuring device 1. As a result of the speed increase, the voltage V1 of the measurement object 4 can be measured in a short time, and when the voltage V1 of the measurement object 4 fluctuates with time, or the voltage V1 of the measurement object 4 is periodic. The voltage V1 can be accurately measured even when the alternating voltage varies with time. Further, according to the voltage measuring device 1A, the reliability of the device itself can be further improved by using the highly reliable variable capacitance circuit 19.

  Further, the voltage measuring devices 1 and 1A employ a configuration in which the synchronous detection circuit 23 is used to extract a frequency component in a predetermined band including the frequency f1 included in the detection signal S4. Although not shown and not shown, a known envelope detection method can be employed instead of the synchronous detection method.

  Further, in the voltage measuring device 1, the current detector 15 is disposed between the capacitance changing function body 13 and the case 11, but, like the voltage measuring device 1B shown in FIG. A current detector 15 may be disposed between the functional body 13 and the functional body 13. In the voltage measuring device 1, the voltage generation circuit 25 is feedback-controlled in an analog manner using the amplification circuit 22, the synchronous detection circuit 23, and the integrator 24 that operate with analog signals, but like the voltage measuring device 1B. The voltage generation circuit 25 can be digitally feedback-controlled by converting the detection signal S3 into digital data.

  Hereinafter, the voltage measuring device 1B will be described with reference to FIG. 7 together with the power measuring device 71 configured using the voltage measuring device 1B. In addition, about the component same as the voltage measuring device 1 among the components of this voltage measuring device 1B, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  The power measuring device 71 is configured to be able to measure DC and AC power, and includes a clamp type probe unit 2B for measuring voltage, a clamp type probe unit 5 for measuring current, and a main unit 3A. Yes. In this case, in the power measuring device 71, the voltage V1 of the measurement object 4 (an electric wire, also referred to as “the electric wire 4” hereinafter) is measured by the probe unit 2B and the constituent elements described later included in the main unit 3A. A voltage measuring device 1B to be measured is configured. In addition, a current measuring device 81 that measures a current I1 flowing in the electric wire 4 is configured by the probe unit 5 and constituent elements described later included in the main unit 3A. The power measuring device 71 measures the power W1 supplied to the electric wire 4 based on the voltage value of the voltage V1 measured by the voltage measuring device 1B and the current value of the current I1 measured by the current measuring device 81. .

  The voltage measuring apparatus 1B includes a probe unit 2B, an oscillation circuit 21, an A / D conversion circuit 72, a CPU 73, a D / A conversion circuit 74, a voltage generation circuit 25, and a voltmeter 26A disposed in the main unit 3A. It is configured with. In this case, the probe unit 2B includes a case 11, a detection electrode 12A, a variable capacitance circuit 19 (a variable capacitance circuit including any one of the capacitance change function bodies 13 and 13A (capacitance change function body 13 in this example)), current A detector 15, a preamplifier 16, and a pair of capacitors 18a and 18b are provided. Each of the detection electrodes 12A is entirely covered with an insulating film RE1 formed of a resin material or the like, and one end side of each of the detection electrodes 12A is pivotally connected to the case 11 so that the other end sides are brought into contact with and separated from each other. It is comprised by a pair of arc-shaped electrodes P1 and P2 comprised freely. With this configuration, the detection electrode 12 </ b> A can clamp the electric wire 4. The variable capacitance circuit 19, the current detector 15, the preamplifier 16, and the pair of capacitors 18a and 18b are disposed in a case 11 covered with an insulating film RE2 formed of a resin material or the like. Further, the capacitance change function body 13 and the current detector 15 are disposed between the detection electrode 12A and the case 11 in a state of being connected in series. Further, in the voltage measurement device 1B, unlike the voltage measurement device 1, the current detector 15 is connected to the detection electrode 12A, and the capacitance changing function body 13 is connected to the case 11. In addition, since the current detector 15 is disposed on the detection electrode 12A side, the detection electrode 12A is prevented from being connected to the reference potential side via the preamplifier 16 in order to prevent the detection electrode 12A from being connected to the reference potential side. Between each input terminal and each end of the current detector 15, DC blocking capacitors 18 a and 18 b are respectively disposed. Similarly to the voltage measuring device 1, the capacitance changing function body 13 and the current detector 15 can be connected in series between the detection electrode 12A and the case 11 in this order. It is not necessary to dispose the capacitors 18a and 18b between each input terminal and each end of the current detector 15.

  The A / D conversion circuit 72 disposed in the main unit 3B, together with the CPU 73 and the D / A conversion circuit 74, constitutes the control unit CNT1 in the present invention, and converts the detection signal S3 as an analog signal into digital data D1. And output to the CPU 73. The CPU 73 executes a detection process for extracting data about a component in a predetermined frequency band including, for example, the frequency f1 of the drive signal S1 from the input digital data D1, and an integration process for integrating the data extracted by this detection process. To do. Further, the CPU 73 outputs the integration data D2 obtained by this integration processing to the D / A conversion circuit 74. Further, as will be described later, the CPU 73 also functions as a part of the current measuring device 81, and based on the digital data D4 output from the A / D conversion circuit 75, the current I1 flowing in the measurement object 4 A current calculation process for calculating (measuring) the current value is also executed. Further, the CPU 73 determines the electric power W1 supplied to the electric wire 4 based on the calculated current value of the current I1 and the voltage value of the feedback voltage V4 (value indicated by the digital data D3) output from the voltmeter 26A. A power calculation process for calculating (measuring) is also executed. The D / A conversion circuit 74 converts the integration data D2 into a DC voltage V3 as an analog signal and outputs it to the voltage generation circuit 25. The voltmeter 26A measures the feedback voltage V4, displays the voltage value, converts the measured voltage value of the feedback voltage V4 into digital data D3, and outputs it to the CPU 73.

  As shown in FIG. 7, the current measuring device 81 includes the probe unit 5, an A / D conversion circuit 75, a CPU 73, and a display device 76 disposed in the main unit 3B. In this case, the probe unit 5 detects the current value of the current I1 flowing through the clamped electric wire 4 in a non-contact manner, and outputs a detection signal S6 whose amplitude changes according to the current value to the A / D conversion circuit 75. The A / D conversion circuit 75 converts the input detection signal S6 into digital data D4 and outputs it to the CPU 73. The CPU 73 calculates the current value of the current I1 based on the digital data D4 by executing the above-described current calculation process, and displays it on the display device 76.

  In the power measuring device 71 configured as described above, the voltage measuring device 1B uses the A / D conversion circuit 72, the CPU 73, and the D / A conversion circuit 74 that constitute the control unit CNT1 to convert the detection signal S3 into digital data D1. In addition, the voltage generation circuit 25 is feedback-controlled in the same manner as each component of the control unit CNT of the voltage measurement device 1 except that the voltage generation circuit 25 is digitally feedback-controlled based on the digital data D1. V4 is matched with the voltage V1.

  On the other hand, in the current measuring device 81, the A / D conversion circuit 75 converts the detection signal S6 detected by the probe unit 5 into digital data D4 and outputs the digital data D4 to the CPU 73. The CPU 73 performs current calculation processing based on the digital data D4. To calculate the current value of the current I1 flowing through the electric wire 4.

  The CPU 73 calculates power based on the voltage value of the feedback voltage V4 (that is, the voltage value of the voltage V1) indicated by the digital data D3 input from the voltmeter 26A and the current value of the current I1 calculated by the current calculation process. By executing the processing, the electric power W1 supplied to the electric wire 4 is calculated (measured) and displayed on the display device 76. Thereby, the measurement of the electric power W1 is completed. In this case, the CPU 73 causes the display device 76 to display the voltage value of the voltage V1 together with the current values of the power W1 and the current I1. In addition, instead of the configuration in which the current value and the voltage value are displayed on the display device 76, a configuration in which the storage device (not shown) stores the current value or the voltage value or transmits the data value or the voltage value to the outside via a data transmission device (not shown). It can also be adopted.

  Thus, in this voltage measuring apparatus 1B, when measuring the voltage V1 of the electric wire 4 as the measuring object 4, the detection signal S3 indicating the current i flowing through the capacitance changing function body 13 is converted into the digital data D1. The voltage generation circuit 25 is digitally feedback-controlled based on the digital data D1. Therefore, the control unit CNT1 (A / D conversion circuit 72, CPU 73, and D / A conversion circuit 74) can be easily configured using a CPU or DSP. Further, in the voltage measuring apparatus 1B, the detection electrode 12A is constituted by a pair of arc-shaped electrodes P1 and P2 that are entirely covered with the insulating coating RE1, and the variable capacitance circuit 19, the current detector 15, the preamplifier 16, and the pair of capacitors. 18a and 18b are disposed in the case 11 covered with the insulating coating RE2. Therefore, since the detection electrode 12A, the variable capacitance circuit 19, the current detector 15, the preamplifier 16, and the pair of capacitors 18a and 18b are not exposed to the outside, the circuit and components are reliably in contact with foreign matter outside the apparatus. Can be avoided. In addition, a highly reliable variable capacitance circuit 19 that does not include a mechanically movable configuration is used. Therefore, the reliability of the voltage measuring device 1B can be sufficiently improved, and the reliability of the power measuring device 71 using the voltage measuring device 1B can be sufficiently improved.

  Further, the power measuring device 71 using the voltage measuring device 1B that performs digital feedback control has been described. However, as illustrated in FIG. 8, the power measuring device 91 is configured using the voltage measuring device 1C that performs analog feedback control. You can also Hereinafter, the power measuring device 91 will be described. In addition, about the same component as the voltage measuring device 1, and the same component as the power measuring device 71, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  The power measuring device 91 is configured to be able to measure DC and AC power, and includes probe units 2B and 5 and a main unit 3B as shown in FIG. In this case, in the power measuring device 91, the voltage measuring device 1C that measures the voltage V1 of the measurement object 4 (as an example, the electric wire 4) is configured by the probe unit 2B and the components described later included in the main unit 3B. Has been. In addition, a current measuring device 81 that measures a current I1 flowing through the electric wire 4 is configured by the probe unit 5 and constituent elements described later included in the main body unit 3B. The power measuring device 91 measures the power W1 supplied to the electric wire 4 based on the voltage value of the voltage V1 measured by the voltage measuring device 1C and the current value of the current I1 measured by the current measuring device 81. .

  The voltage measuring apparatus 1C includes a probe unit 2B, and an oscillation circuit 21, a control unit CNT, a voltage generation circuit 25, and a voltmeter 26A that are disposed in the main unit 3B. In this case, the control unit CNT generates the DC voltage V3 based on the detection signal S3 as an analog signal and outputs the DC voltage V3 to the voltage generation circuit 25, thereby feedback-controlling the feedback voltage V4 in an analog manner, so that the feedback voltage V4 Is made to coincide with the voltage V1. The current measuring device 81 includes the probe unit 5, an A / D conversion circuit 75, a CPU 73, and a display device 76 that are disposed in the main unit 3A. In this case, the CPU 73 calculates the current value of the current I1 based on the digital data D4 input from the A / D conversion circuit 75 and displays it on the display device 76 by executing a current calculation process. Further, the CPU 73 causes the display device 76 to display the voltage value of the feedback voltage V4 (voltage V1) based on the digital data D3 input from the voltmeter 26A. Further, the CPU 73 calculates power based on the voltage value of the feedback voltage V4 (that is, the voltage value of the voltage V1) indicated by the digital data D3 input from the voltmeter 26A and the current value of the current I1 calculated by the current calculation process. By executing the processing, the electric power W1 supplied to the electric wire 4 is calculated (measured) and displayed on the display device 76.

  Also in the power measuring apparatus 91, the reliability of the voltage measuring apparatus 1C can be sufficiently improved in the same manner as the voltage measuring apparatus 1B. As a result, the reliability of the power measuring apparatus 91 itself using the voltage measuring apparatus 1C is improved. It can be improved sufficiently.

  Further, in the voltage measuring devices 1, 1B, and 1C described above, the current detector 15 is configured using a resistor. However, as long as it is an impedance element, the current detector 15 may be configured not only by a resistor but also by a capacitor or a coil. These can also be combined. By using the impedance element in this way, the voltage value of the voltage V2 generated when the current i flows can be arbitrarily changed by changing the impedance value of the impedance element. For this reason, as a result of being able to set the voltage V2 generated in the current detector 15 to an appropriate value in accordance with the level of the voltage of the measurement object 4, the measurement object 4 has a wide voltage range from low voltage to high voltage. The voltage can be measured accurately. Also, instead of the impedance element, either a resonance circuit including various resonators such as a ceramic resonator or a crystal resonator, and an LC resonance circuit (series resonance circuit or parallel resonance circuit) composed of a coil and a capacitor are used. It can also be used. Among these resonance circuits, the resonance circuit including the resonator and the LC parallel resonance circuit have a characteristic that the impedance becomes maximum at a specific frequency (resonance frequency). For this reason, as shown in FIG. 11 as an example, the current detector 15 is configured using an LC parallel resonance circuit composed of a coil 15a and a capacitor 15b, and this specific frequency is subjected to capacitance modulation of the capacitance changing function body 13. By matching with the frequency, even when noise having a frequency different from the capacitance modulation frequency is superimposed on the current i, the current i among the voltage components included in the voltage V2 generated at both ends of the current detector 15. Since the voltage component due to the noise can be made sufficiently larger than the voltage component due to the noise, the noise can be suppressed. On the other hand, the LC series resonance circuit has a characteristic that the impedance as a whole becomes minimum (zero) at a specific frequency (resonance frequency). In this case, the voltage across the capacitor (the same applies to the coil) constituting the LC series resonance circuit is maximized. For this reason, as shown in FIG. 12, as an example, the current detector 15 is configured by using an LC series resonance circuit composed of a coil 15a and a capacitor 15b, and this specific frequency is matched with the capacitance modulation frequency. By adopting a configuration in which the preamplifier 16 detects the voltage across the capacitor 15b (or the coil 15a) as the voltage V2, even when noise having a frequency different from the capacitance modulation frequency is superimposed on the current i, In the same manner as the LC parallel resonance circuit, it is possible to suppress the generation of voltage due to this noise generated at both ends of the current detector 15. Therefore, by configuring the current detector 15 with these resonance circuits, the value of the voltage generated in the resonance circuit when the current i flows can be arbitrarily changed by changing the impedance value during resonance of the resonance circuit. Therefore, the voltage V1 of the measuring object 4 can be measured over a wide voltage range from a low voltage to a high voltage. Moreover, since the current i flowing through the resonance circuit can be detected as a larger voltage by changing the capacitance C1 of the capacitance change function body 13 at the resonance frequency of the resonance circuit, the voltage signal caused by this noise can be detected. As a result of being able to reduce mixing in the detection signal S3, the noise resistance performance of the voltage measuring devices 1, 1B, 1C can be enhanced. Therefore, the voltage V1 of the measuring object 4 can be measured with few malfunctions. Further, instead of a configuration in which the current is converted into a voltage by using an impedance element such as a resistor or a resonance circuit, a configuration in which the current is directly detected can be employed. In this configuration, an electromagnetic induction type current detector (CT type current detector) is used, a Hall element, a magnetic bridge, a flux gate sensor, an MI (magnetic impedance) sensor, an MR (magnetoresistance effect) sensor, a GMR ( It can be configured using a magnetic sensor such as a giant magnetoresistance effect) sensor and a TMR (tunnel magnetoresistance effect) sensor.

  In the voltage measuring devices 1, 1A, 1B, and 1C, the example in which the detection signal S3 generated by the preamplifier 16 is directly input to the amplifier circuit 22 or the A / D conversion circuit 72 has been described. The detection signal S3 can also be input to the amplifier circuit 22 or the A / D conversion circuit 32 via In this case, by configuring this filter circuit to selectively pass a signal having the same frequency as the capacity modulation frequency of the capacity change function body 13, noise having a frequency different from the capacity modulation frequency is superimposed on the current i. Even when it is present, this noise can be prevented from being mixed into the detection signal S3. Therefore, the noise resistance performance of the voltage measuring devices 1, 1A, 1B, 1C can be improved.

  Moreover, although the example which applies voltage measuring device 1B, 1C to power measuring device 71,91 was demonstrated, voltage measuring device 1,1A, 1B, 1C detects the surface potential of the photosensitive drum in copying machines, such as a laser printer. It can be used as a surface electrometer. Moreover, it can also be used as a detector for detecting the position of the electrical wiring arranged in the wall. By using the voltage measuring device according to the present invention for these devices, the reliability (including durability and weather resistance) of these devices can be sufficiently improved. Furthermore, the present invention can also be applied to a substrate inspection apparatus that inspects a disconnection or the like of a printed pattern formed on a printed circuit board.

  In the voltage measuring devices 1, 1A, 1B, and 1C, when the feedback voltage V4 reaches the voltage V1 and becomes constant, that is, when the current i becomes zero ampere or the voltage V5 between both ends becomes zero volts. When the feedback voltage V4 is measured as the voltage V1 of the measurement object 4, the voltage V1 is measured with high accuracy. If the measurement accuracy is acceptable, the current i and the voltage between both ends are measured. It is also possible to employ a configuration in which the feedback voltage V4 when V5 becomes a predetermined value (for example, several milliamperes or several millivolts) or less is measured as the voltage V1 of the measurement object 4. Further, a configuration in which the feedback voltage V4 when the potential difference (V1−V4) reaches a predetermined value (for example, several hundred millivolts) or less is measured as the voltage V1 of the measurement object 4 can be employed. By adopting this configuration, the voltage V1 of the measuring object 4 can be measured in a shorter time with an acceptable accuracy.

  Further, each structural unit of each capacitance changing function body 13 described above is configured by one diode (equivalently, one diode in the case of FIG. 5) as shown in FIGS. However, the present invention is not limited to this. For example, taking the structural unit 31 shown in FIG. 2 as an example, a possible configuration of a structural unit including a variable capacitance element (diode as an example) will be described. Between the connection point A and the diode 41 and between the connection point B and One or more of at least one of other variable capacitance elements (for example, a diode), a resistor, a capacitor, and a coil can be disposed between at least one of the diodes 41. When other variable capacitance elements (diodes as an example) are provided, in addition to the configuration in which a plurality of variable capacitance elements are connected in series as described above, some variable capacitance elements are connected in parallel. It can also be arranged to be connected. However, when a plurality of variable capacitance elements (for example, variable capacitance diodes or silicon diodes) are arranged in one structural unit, all the diodes must be arranged in the same direction in the structural unit. There is. A capacitor can be connected in parallel to the diode 41.

  Further, the configuration in which all the variable capacitance diodes 41 to 44 shown in FIG. 2 are replaced with the general diodes 51 to 54 has been described with reference to FIG. 3, but both the variable capacitance diode and the general diode are basically included. For example, in the capacitance change function body 13 shown in FIG. 2, at least one of the diodes 41 to 44 can be replaced with a general diode. For example, the variable capacitance diode and the general diode Can be used together. However, a variable capacitance diode and a general diode have different electrostatic capacities when a reverse bias is applied, so that they satisfy the equilibrium condition of the bridge circuit and are arranged on both sides of the connection points A and C as a reference. The respective structural units 31, 32 and the respective structural units 34, 33 that are provided are line-symmetric or each of the structural units 31, 34, 34 and 33 that are disposed on both sides with respect to the connection points B, D. It is necessary to configure so that the structural units 32 and 33 are line-symmetric.

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. FIG. 6 is another circuit diagram of the capacity changing function body 13 of the voltage measuring device 1. It is a characteristic view which shows the time change of the feedback voltage V4. 3 is a circuit diagram of a capacity changing function body 13A of the voltage measuring device 1. FIG. It is a block diagram of voltage measuring device 1A. It is a block diagram of voltage measuring device 1B and electric power measuring device 71 using the same. It is a block diagram of voltage measuring device 1C and electric power measuring device 91 using the same. 3 is a circuit diagram illustrating a configuration example of a current detector 15. FIG. FIG. 6 is a circuit diagram illustrating another configuration example of the current detector 15.

Explanation of symbols

1, 1A, 1B, 1C Voltage measurement device 3, 3A, 3B Main unit 4 Measurement object 11 Case 12 Detection electrode 13, 13A Capacity changing function body 14 Drive circuit 14a Transformer 14b DC power supply 14c Secondary winding 15 Current detector DESCRIPTION OF SYMBOLS 19 Variable capacity circuit 25 Voltage generation circuit 31,32,33,34 Structural unit 71,91 Power measuring device C1 Capacitance CNT, CNT1 Control part i Current S2 Drive signal V1 Voltage of measurement object V4 Feedback voltage (reference potential)

Claims (11)

A first structural unit, a second structural unit, a third structural unit, and a fourth structural unit each including at least one variable capacitance element are connected in a ring shape in this order, and the first structural unit And a capacitance changing function body in which the product of each impedance of the third structural unit and the product of the impedances of the second structural unit and the fourth structural unit are defined to be the same or substantially the same,
A transformer for inducing an AC component in a secondary winding and a DC power source for generating a DC voltage, wherein the secondary winding and the DC power source of the transformer are the first structural unit and the second configuration; A series connection point between the connection point of the unit and the connection point of the third structural unit and the fourth structural unit is applied in series to the capacitance change function body. A variable capacitance circuit comprising: a drive circuit that changes the capacitance of the capacitance change function body.   The variable capacitance circuit according to claim 1, wherein the variable capacitance element includes a P-type semiconductor and an N-type semiconductor joined to each other.   The variable capacitance element includes a diode formed of the P-type semiconductor and the N-type semiconductor, and each of the diodes included in the first structural unit and the fourth structural unit includes the four structures. The respective diodes arranged in the same direction in the annular circuit constituted by the unit and included in the second structural unit and the third structural unit are arranged in the annular circuit. The variable capacitance circuit according to claim 2, wherein the diode is disposed in a direction opposite to a direction of each of the diodes in the four structural units.   A set of the P-type semiconductor and the N-type semiconductor included in the first structural unit and the P-type semiconductor and the N-type semiconductor included in the second structural unit; and the third At least one set of the P-type semiconductor and the N-type semiconductor included in the structural unit and the P-type semiconductor and the N-type semiconductor included in the fourth structural unit is one transistor. The variable capacitance circuit according to claim 2, comprising: A voltage measuring device configured to be able to measure the voltage of a measurement object,
A detection electrode capable of facing the measurement object, and the variable capacitance circuit according to any one of claims 1 to 4,
In the variable capacitance circuit, a connection point between the first structural unit and the fourth structural unit is located on the detection electrode side, and a connection point between the second structural unit and the third structural unit is a reference potential. A voltage measuring device disposed between the detection electrode and the reference potential so as to be positioned on the side. A voltage generation circuit for generating the reference potential; and a control unit;
The voltage measurement device according to claim 5, wherein the control unit changes the voltage of the reference potential with respect to the voltage generation circuit when the variable capacitance circuit changes the capacitance.   The control unit includes a current flowing between the detection electrode and the reference potential via the variable capacitance circuit when the capacitance changes, or an end of the variable capacitance circuit on the detection electrode side and the current The voltage measurement device according to claim 6, wherein the voltage of the reference potential is changed with respect to the voltage generation circuit so that a voltage generated between the reference potential side and the end portion on the reference potential side is reduced. An impedance element disposed in series with the variable capacitance circuit between the detection electrode and the reference potential;
The voltage measurement according to claim 7, wherein the control unit changes the voltage of the reference potential with respect to the voltage generation circuit so that a voltage generated in the impedance element decreases when the current flows through the impedance element. apparatus. A resonance circuit disposed in series with the variable capacitance circuit between the detection electrode and the reference potential;
The voltage measurement according to claim 7, wherein the control unit changes the voltage of the reference potential with respect to the voltage generation circuit so that a voltage generated in the resonance circuit decreases when the current flows in the resonance circuit. apparatus.   The control unit receives a detection signal whose voltage value changes according to the value of the current or the value of the voltage generated between the end on the detection electrode side and the end on the reference potential side. An A / D conversion circuit for converting to digital data is provided, and the voltage of the reference potential is changed with respect to the voltage generation circuit so that the voltage value of the detection signal decreases based on the digital data. The voltage measuring device according to any one of the above. A current measuring device for measuring the current flowing through the measurement object;
The voltage measuring device according to any one of claims 5 to 10, which measures the voltage of the measurement object,
A power measurement device that measures power based on the current measured by the current measurement device and the voltage measured by the voltage measurement device.

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