JP2012122781A - Resistance measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous measurement of a pure resistance value of a measurement target having an inductance component connected to a pure resistance component.SOLUTION: The resistance measurement device includes a current supply unit 2 for supplying an AC constant current I to a measurement target 8 to output a synchronous signal St, a voltage detection unit 3 for detecting and outputting an AC signal S1 generated between both ends of the measurement target 8, a synchronous flow-rectifying unit 4 for inverting and outputting the AC signal S1 at each half period of the synchronous signal St to generate a synchronous flow-rectifying signal Sre, and smoothing this to output a synchronous flow-rectifying voltage Vr, an A/D conversion unit 5 for converting the synchronous flow-rectifying voltage Vr into voltage data Dv, and a processing unit 6 for calculating a resistance value Rx of the pure resistance of the measurement target 8 based on the voltage value of the AC signal S represented by the voltage data Dv and the current value of the AC constant current I. The synchronous flow-rectifying unit 4 limits the amplitude of a negative polarity side for a waveform at the latter half period of the synchronous signal St among the waveforms of the synchronous flow-rectifying signal Sre to a prescribed value Vd1 less than the maximum amplitude of the AC signal S1 of the negative polarity side.

Description

  The present invention supplies an AC constant current to an object to be measured and synchronously rectifies a voltage signal generated in the object to be measured due to the supply of the AC constant current, and the voltage value of the DC voltage obtained by the synchronous rectification and the AC The present invention relates to a resistance measuring device that measures a resistance value of a measurement object based on a current value of a constant current.

  As this type of resistance measurement device, a current measurement device (hereinafter referred to as a resistance measurement device) operable in a resistance measurement mode disclosed in Patent Document 1 below is known. This resistance measuring device includes an AC constant current source, a capacitor, an AC amplifier, a synchronous rectifier circuit, an A / D converter, and a CPU.

  In this resistance measuring apparatus, an AC constant current source supplies an AC constant current having a constant frequency to an object to be measured (hereinafter also referred to as “measurement object”. Voltage drop generated in the measurement object due to the supply of the AC constant current. Is detected as a voltage signal at the voltage detection terminal, and then the capacitor extracts only the AC component from the detected voltage signal (blocks the DC component), and the AC amplifier appropriately amplifies the signal output from the capacitor. The synchronous rectifier circuit receives the amplified AC signal, and inverts and averages the AC signal every half cycle of the frequency of the AC constant current, thereby proportional to the DC resistance component to be measured. A synchronous rectified output (DC voltage) is generated, and then the A / D converter converts the synchronous rectified output into digital data, and the CPU converts the measurement rectified output based on the digital data. To calculate the DC resistance.

JP 2000-292463 A (page 3-4, FIG. 1)

  However, the resistance measuring apparatus has the following problems to be solved. That is, in this resistance measuring apparatus, the synchronous rectifier circuit inverts the input AC signal every half cycle of the frequency of the AC constant current, and specifically, for example, as shown in FIG. The inverted AC signal S2 is generated by inverting S1. Next, based on the synchronization signal St synchronized with the AC constant current, when the synchronization signal St is at the High level (the first half cycle T1 of the synchronization signal St), the AC signal S1 is output and the Low level (the second half of the synchronization signal St) is output. In the half cycle T2), the synchronous rectification signal Sre is generated by outputting the inverted AC signal S2. Subsequently, the synchronous rectification signal Sre is averaged to generate a synchronous rectification voltage (DC voltage) Vr. In this case, the synchronous rectified voltage Vr becomes a voltage proportional to the DC resistance component to be measured when the synchronization signal St and the AC signal S1 are substantially synchronized (when the phase difference is small). Based on the synchronous rectified voltage Vr, the DC resistance (pure resistance) to be measured is measured.

  However, for example, in a measurement object in which an inductance component is connected in series to a pure resistance, a synchronous rectification is generated based on an AC constant current supplied to the measurement object and a voltage drop generated in the measurement object. As shown in FIG. 10, there is a phase difference between the AC signal input to the circuit, that is, between the synchronization signal St and the AC signal S1, and particularly when the pure resistance to be measured is small with respect to the inductance component. When the influence of the inductance component is large, this phase difference is close to 90 ° as shown in FIG. In this state, the synchronous rectification signal Sre has an integral value of the positive-side portion A1 and an integral value of the negative-side portion A2 (the hatched portion in the first half cycle T1 of one cycle of the synchronization signal St. And the integrated value of the positive side portion A3 and the integrated value of the negative side portion A4 (see the shaded portion) are substantially the same in the latter half cycle T2. The synchronous rectification voltage Vr obtained by averaging the synchronous rectification signal Sre has a value very close to zero volts.

  Thus, for example, as in the case of the ground resistance test, the measured resistance value (the ground resistance at the measurement point) is compared with a predetermined threshold value, and the measured resistance value is the threshold value. If the measured resistance value is below the threshold value, the test object is determined to be normal. There is a problem to be solved that there is a risk of discriminating that it exists. Similar problems also occur in a measurement object in which a capacitance component is connected to a pure resistance.

  The present invention has been made to solve such a problem, and provides a resistance measuring device capable of avoiding an erroneous measurement of a pure resistance value of a measurement object in which an inductance component or a capacitance component is connected to a pure resistance component. The main purpose is to do.

  In order to achieve the above object, the resistance measuring apparatus according to claim 1 includes a current supply unit that supplies an alternating current to a measurement target, and a signal output unit that outputs a synchronization signal having the same frequency and phase as the alternating current. And a voltage detector that detects and outputs an AC signal generated between both ends of the measurement object when the AC current flows through the measurement object, and inputs the synchronization signal and the AC signal, A synchronous rectification signal is generated by inverting and outputting the alternating current signal for every half cycle of the synchronous signal, and the synchronous rectification signal is smoothed and output as a synchronous rectification voltage. And a display unit that displays the pure resistance of the measurement object based on the synchronous rectification unit, wherein the synchronous rectification unit includes a first half cycle and a second half of the synchronous signal in the waveform of the synchronous rectification signal. The amplitude of the predefined polarity for the waveform in at least one of the half cycle is limited to less than a small predetermined value than the maximum amplitude of the AC signal of the polarity of the.

  The resistance measurement device according to claim 2 is the resistance measurement device according to claim 1, wherein the display unit drives the pointer based on the synchronous rectification voltage on the display panel on which the scale is displayed, to thereby perform the pure measurement. It consists of an analog meter that indicates resistance.

  The resistance measuring device according to claim 3 is the resistance measuring device according to claim 1, wherein an A / D converter that converts the synchronous rectified voltage into voltage data, and the AC signal represented by the voltage data. The apparatus includes a processing unit that calculates a pure resistance of the measurement target based on a voltage value and a current value of the alternating current, and displays the calculated pure resistance on the display unit.

  Further, the resistance measuring device according to claim 4 is the resistance measuring device according to any one of claims 1 to 3, wherein the synchronous rectification unit inverts the input AC signal and outputs the inverted AC signal as an inverted AC signal. A circuit, a switching circuit that generates the synchronous rectification signal by alternately outputting the input AC signal and the inverted AC signal every half cycle of the synchronous signal, and the synchronous rectification by smoothing the synchronous rectification signal A smoothing circuit for generating a voltage, and an absolute value of the power supply voltage on the polarity side defined in the inverting circuit is defined as the specified value.

  Further, the resistance measurement device according to claim 5 is the resistance measurement device according to any one of claims 1 to 3, wherein the synchronous rectification unit inverts the input AC signal and outputs the inverted AC signal. A circuit, a voltage limiting circuit that outputs the predetermined polarity side amplitude of at least one of the AC signal and the inverted AC signal to be equal to or lower than the specified value, and is output from the voltage limiting circuit. A switching circuit that generates the synchronous rectification signal by alternately outputting the other one of the one signal and the AC signal and the inverted AC signal every half cycle of the synchronization signal; and And a smoothing circuit that smoothes and generates the synchronous rectified voltage.

  Moreover, the resistance measuring device according to claim 6 is the resistance measuring device according to any one of claims 1 to 3, wherein the synchronous rectification unit inverts the input AC signal and outputs the inverted AC signal. A circuit, a switching circuit that generates the synchronous rectification signal by alternately outputting the input AC signal and the inverted AC signal every half cycle of the synchronous signal, and the predetermined polarity in the synchronous rectification signal A voltage limiting circuit for limiting and outputting the amplitude on the side to be equal to or less than the specified value, and a smoothing circuit for generating the synchronous rectified voltage by smoothing the synchronous rectified signal output from the voltage limiting circuit.

  2. The resistance measuring apparatus according to claim 1, wherein the synchronous rectification unit has a predetermined polarity side with respect to a waveform in at least one of the first half cycle and the second half cycle of the synchronous signal among the waveforms of the synchronous rectification signal. Is limited to a value less than a specified value smaller than the maximum amplitude of the AC signal on the polarity side.

  Therefore, according to this resistance measurement apparatus, when the inductance component included in the measurement target is sufficiently smaller than the pure resistance and the AC signal is almost synchronized with the synchronization signal, the resistance of the measurement target While the value can be measured accurately, the influence on the pure resistance such as the inductance component included in the measurement object is increased, the phase of the AC signal is shifted from the synchronization signal, and the phase difference between the two signals is approximately 90 °. Even in this state, it is possible to reliably avoid a situation in which the resistance value of the pure resistance to be measured which is not originally zero ohms is erroneously measured as a value close to zero ohms.

  According to the resistance measuring apparatus of the second aspect, since the display unit for displaying the resistance value of the measurement object is configured by the analog meter, the resistance value can be displayed with a simple configuration.

  Further, according to the resistance measuring apparatus of the third aspect, the A / D converter that converts the synchronous rectified voltage into voltage data, the voltage value of the AC signal represented by the voltage data, and the current value of the AC current are used. By providing a processing unit that calculates the pure resistance to be measured and displays it on the display unit, the display unit can be configured with a digital display such as an LCD, and the measured resistance value can be easily confirmed. Can be displayed.

  According to the resistance measuring apparatus of the fourth aspect, the absolute value of the power supply voltage on the polarity side defined in advance among the power supply voltages supplied as the operating voltage to the inverting circuit of the synchronous rectification unit is set to the specified value. By defining, the amplitude of the waveform in one of the first half cycle and second half cycle of the synchronous signal of the synchronous rectification signal waveform is limited to the specified value or less without adding a special circuit. Thus, it is possible to reliably avoid a situation in which the resistance value of the pure resistance to be measured that is not originally zero ohms is erroneously measured as a value close to zero ohms.

  According to the resistance measuring device of claim 5, the basic configuration of the synchronous rectification unit such as the inverting circuit, the switching circuit, and the smoothing circuit includes a predetermined polarity side for at least one of the AC signal and the inverted AC signal. By simply adding a voltage limiter circuit that limits the output amplitude to a specified value or less, it is possible to reliably avoid a situation where the resistance value of the pure resistance to be measured, which is not originally zero ohms, is close to zero ohms. can do.

  According to the resistance measuring device of the sixth aspect, the basic polarity of the synchronous rectification unit such as the inverting circuit, the switching circuit, and the smoothing circuit is limited to a predetermined polarity side amplitude in the synchronous rectification signal below a predetermined value. The voltage value of the synchronous rectified voltage output from the smoothing circuit can be further increased by adding a voltage limiting circuit that outputs the output voltage, so the resistance value of the pure resistance to be measured, which is not originally zero ohms, is reduced to zero ohms. The situation of erroneous measurement as a close value can be avoided more reliably.

1 is a configuration diagram of a resistance measuring device 1. FIG. It is a timing chart for demonstrating operation | movement of the resistance measuring apparatus 1 when alternating current signal S1 is synchronizing with the synchronizing signal St. It is a timing chart for demonstrating operation | movement of the resistance measurement apparatus 1 when alternating current signal S1 advances substantially 90 degrees with respect to the synchronizing signal St. It is a timing chart for demonstrating operation | movement of the resistance measuring apparatus in the structure which restrict | limits the negative amplitude to the negative power supply voltage Vd about the waveform in the first half cycle of the synchronous signal St among the waveforms of the synchronous rectification signal Sre. . It is a block diagram of 4 A of synchronous rectification parts. It is a block diagram of the synchronous rectification part 4B. It is a timing chart for demonstrating operation | movement of the resistance measuring apparatus provided with the synchronous rectification part 4B. It is a lineblock diagram of resistance measuring device 1A. It is a timing chart for demonstrating operation | movement of the conventional resistance measuring apparatus when alternating current signal S1 is synchronizing with the synchronizing signal St. It is a timing chart for demonstrating operation | movement of the conventional resistance measuring apparatus when alternating current signal S1 advances substantially 90 degrees with respect to the synchronizing signal St.

  Hereinafter, an embodiment of a resistance measuring device will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the resistance measuring apparatus 1 includes a current supply unit 2, a voltage detection unit 3, a synchronous rectification unit 4, an A / D conversion unit 5, a processing unit 6, and a display unit 7. The resistance value Rx of the resistor R is measured by the four probe method as an example.

  The current supply unit 2 has an AC current I having a constant current value (known) defined in advance (that is, an AC constant current, a sinusoidal current having a constant amplitude in this example. Hereinafter, it is also referred to as an AC constant current I). ) And supplied to the measuring object 8. Further, the current supply unit 2 generates and outputs a synchronization signal St having the same frequency as the AC constant current I and having the same phase. Thereby, the current supply unit 2 also functions as a signal output unit that outputs the synchronization signal St. For example, the voltage detector 3 is configured by an AC amplifier circuit (not shown), and detects an AC voltage V as an AC signal generated between both ends of the measurement object 8 when the AC constant current I is supplied. Output (in this example, output as AC signal S1).

  The synchronous rectification unit 4 receives the synchronization signal St and the AC signal S1, generates the synchronous rectification signal Sre by inverting and outputting the AC signal S1 every half cycle of the synchronization signal St, and the generated synchronization The rectified signal Sre is smoothed and a synchronous rectified voltage (DC voltage) Vr is output. Thereby, the synchronous rectification unit 4 functions as a synchronous detection circuit.

  In this example, as an example, the synchronous rectification unit 4 includes an inverting circuit 11, a switching circuit 12, and a smoothing circuit 13. For example, the inverting circuit 11 has an AC signal S1 input to the inverting input terminal via the input resistor 11a, and a non-inverting input terminal connected to the reference potential (ground potential). The operational amplifier 11c is configured to invert and amplify the AC signal S1 with an amplification factor defined by the resistance value of the feedback resistor 11b and output the inverted signal as an inverted AC signal S2. In this example, the resistance value of the input resistor 11a and the resistance value of the feedback resistor 11b are defined to be the same, and the amplification factor is defined to be 1. Further, one of positive power supply voltage (positive power supply voltage) Vc and negative power supply voltage (negative power supply voltage) Vd supplied as an operating voltage to the operational amplifier 11c (in this example, The absolute value of positive power supply voltage Vc) is defined to be higher than the maximum amplitude of AC signal S1, and the absolute value of the other (in this example, negative power supply voltage Vd) is lower than the maximum amplitude of AC signal S1. It is defined to a specified value (Vd1). That is, the negative power supply voltage Vd is defined by the voltage value (−Vd1).

  With this configuration, as shown in FIGS. 2 and 3, the inverting circuit 11 inverts and amplifies the negative waveform of the input AC signal S1 at the same magnification and outputs it as the positive waveform of the inverted AC signal S2. . On the other hand, when the inverting circuit 11 inverts and amplifies the positive waveform of the input AC signal S1 to generate the negative AC signal S2, the absolute value is the absolute value (specified value) of the negative power supply voltage Vd. Amplifying operation of Vd1) or higher is limited. Therefore, in the inverting circuit 11, the waveform on the positive polarity side is an inverted waveform of the waveform on the negative side of the AC signal S1, and the amplitude of the waveform on the negative polarity side (predetermined polarity side) is less than or equal to the specified value (Vd1). A limited inverted AC signal S2 is generated and output. In the inverting circuit 11 in which the negative power supply voltage Vd is regulated to the above voltage value (−Vd1), the amplitude of the waveform on the negative side of the inverted AC signal S2 to be output is actually this voltage value (−Vd1). ), Which is limited to a value slightly smaller than the absolute value (that is, the specified value (Vd1)) by a value determined by the configuration of the inverting circuit 11, in this example, in order to facilitate understanding of the invention, the specified value (Vd1) The following description will be made assuming that it is limited.

  The switching circuit 12 alternately outputs an alternating current signal S1 input to the input terminal a and an inverted alternating current signal S2 input to the input terminal b in every half cycle of the synchronous signal St in synchronization with the synchronous signal St. c is output as a synchronous rectification signal Sre.

  With the above configuration, the synchronous rectification unit 4 inverts the AC signal S1 every half cycle of the synchronization signal St, and also has a negative polarity side (predetermined polarity side) for the waveform in the latter half cycle of the synchronization signal St. Is limited to a negative power supply voltage Vd (an example of a predetermined constant voltage) or less, and the synchronous rectification signal Sre is output.

  The smoothing circuit 13 is configured by a low-pass filter as an example, and outputs a synchronous rectified voltage Vr as shown in FIGS. 1, 2, and 3 by smoothing the synchronous rectified signal Sre. In this case, as shown in FIG. 2, the synchronous rectification voltage Vr is combined with the configuration in which the AC constant current I is supplied from the current supply unit 2 to the measurement object 8 when the AC signal S1 is synchronized with the synchronization signal St. The voltage is proportional to the resistance value Rx of the pure resistance R of the measuring object 8.

  The A / D converter 5 receives the synchronous rectified voltage Vr and converts it into voltage data Dv (which is also data indicating the AC voltage V generated between both ends of the measurement object 8) indicating the absolute value of the voltage value. To the processing unit 6. The processing unit 6 includes a CPU and a memory (both not shown), and calculates a resistance value Rx of the pure resistance R of the measurement target 8 based on the voltage data Dv. In addition, the processing unit 6 causes the display unit 7 to display the calculated resistance value Rx of the pure resistance R. In this example, as an example, the display unit 7 is configured by a digital display such as an LCD (Liquid Crystal Display) capable of displaying numerical values. Therefore, the processing unit 6 displays a numerical value indicating the resistance value Rx of the pure resistance R on the screen of the display unit 7.

  Next, operation | movement of the resistance measuring apparatus 1 is demonstrated with reference to drawings.

  In the resistance measuring apparatus 1, the current supply unit 2 supplies an AC constant current I to the measurement object 8, generates a synchronization signal St, and outputs it to the switching circuit 12 of the synchronous rectification unit 4. In this state, the voltage detection unit 3 detects the AC voltage V generated across the measurement object 8 and outputs it as an AC signal S1.

  In the synchronous rectification unit 4, the operational amplifier 11c of the inverting circuit 11 inverts and amplifies the AC signal S1 in a state where the absolute value of the negative power supply voltage Vd is regulated to a voltage lower than the maximum amplitude of the AC signal S1 as described above. By doing so, the waveform on the positive polarity side becomes an inverted waveform of the waveform on the negative polarity side of the AC signal S1, and the waveform on the negative polarity side is the waveform on the positive polarity side of the AC signal S1 limited by the negative power supply voltage Vd. An inverted AC signal S2 having an inverted waveform is generated and output (see FIGS. 2 and 3).

  The switching circuit 12 inputs the AC signal S1 input to the input terminal a and the input terminal b by alternately connecting the input terminal a and the input terminal b to the output terminal c in synchronization with the synchronization signal St. The inverted AC signal S2 is alternately output as the synchronous rectification signal Sre from the output terminal c every half cycle of the synchronization signal St. In this example, as an example, the switching circuit 12 outputs the AC signal S1 as the synchronous rectification signal Sre when the synchronization signal St is at a high level (the first half cycle of the synchronization signal St) T1, as shown in FIGS. At the low level (half cycle of the second half of the synchronization signal St) T2, the inverted AC signal S2 is output as the synchronous rectification signal Sre. Further, the smoothing circuit 13 smoothes the synchronous rectification signal Sre and outputs a synchronous rectification voltage Vr. Next, the A / D conversion unit 5 converts the synchronous rectified voltage Vr into voltage data Dv, and the processing unit 6 calculates the resistance value Rx of the pure resistance R based on the voltage data Dv, and the display unit 7 To display.

  In this case, in this example, the inverted AC signal S2 output from the inverting circuit 11 is limited in the amplitude of the waveform on the negative polarity side by the absolute value (specified value Vd1) of the negative power supply voltage Vd. 2 is sufficiently smaller than the pure resistance R (the influence of the inductance component is extremely small), the AC signal S1 is synchronized with the synchronization signal St as shown in FIG. 2 (that is, the AC signal). S1 and the synchronization signal St are in phase with each other (the phase difference is zero). As a result, the synchronous rectification signal Sre output from the switching circuit 12 is alternately output as the synchronous rectification signal Sre only in the positive waveform of the AC signal S1 and the inverted AC signal S2 (the AC signal S1 is full-wave rectified. It is output as a signal with the same waveform as when). For this reason, the synchronous rectification voltage Vr output from the synchronous rectification unit 4 is a voltage proportional to the resistance value Rx of the pure resistance R for the measurement target 8. Therefore, by checking the resistance value Rx displayed on the display unit 7, the resistance value Rx of the measuring object 8 can be accurately measured.

  On the other hand, the influence of the inductance component included in the measurement object 8 on the pure resistance R is increased. For example, as shown in FIG. 3, when the AC signal S1 is approximately 90 ° ahead of the synchronization signal St, Since the synchronous rectified voltage Vr is not a voltage proportional to the resistance value Rx of the pure resistance R for the measurement object 8, the resistance value Rx of the measurement object 8 cannot be measured accurately. However, even in this state, in this example, the amplitude of the waveform on the negative polarity side of the inverted AC signal S2 is limited to the specified value Vd1 (that is, the minimum waveform of the waveform on the negative polarity side of the inverted AC signal S2). Since the value is limited to the voltage value −Vd1), the synchronous rectification signal Sre output from the switching circuit 12 has a waveform in the second half cycle T2 of the synchronization signal St of the waveform (the synchronization signal St is at the low level). Only the amplitude with a predetermined polarity (negative polarity) is limited to a predetermined value Vd1 or less.

  As a result, the synchronous rectification signal Sre has an integral value of the positive side portion A1 and an integral value of the negative side portion A2 in the first half cycle T1 of one cycle of the synchronization signal St (see the hatched portion). Are substantially the same, but in the latter half cycle T2, the integral value of the positive side portion A3 and the integral value of the negative side portion A4 (see the hatched portion) are different (positive side portion A3). Integral value> integral value of negative portion A4). For this reason, the synchronous rectification voltage Vr output from the smoothing circuit 13 of the synchronous rectification unit 4 is a value obtained by dividing by 2 the value obtained by subtracting the integral value of the negative side portion A4 from the integral value of the positive side portion A3. As shown in FIG. 3, it is output as a voltage other than zero volts. Therefore, in the resistance measuring apparatus 1, when the influence of the inductance component included in the measuring object 8 on the pure resistance R is large, the resistance value Rx of the pure resistance R of the measuring object 8 cannot be measured accurately, but originally zero ohms. A situation in which the resistance value Rx of the pure resistance R of the measurement object 8 that is not is measured as a value close to zero ohms under the influence of the inductance component is avoided.

  Thus, in this resistance measuring apparatus 1, the synchronous rectification unit 4 has a predetermined polarity (in this example, negative polarity) for the waveform in the latter half cycle T2 of the synchronous signal St of the waveform of the synchronous rectified signal Sre. ) Is limited to a specified value Vd1 (the absolute value of the negative power supply voltage Vd) or less.

  Therefore, according to the resistance measuring apparatus 1, when the inductance component included in the measurement object 8 is sufficiently smaller than the pure resistance R and the AC signal S1 is substantially synchronized with the synchronization signal St, While the resistance value Rx of the measuring object 8 can be accurately measured, the influence of the inductance component included in the measuring object 8 on the pure resistance R increases, and the phase of the AC signal S1 with respect to the synchronization signal St shifts, so that both signals Even in a state where the phase difference between St and S1 is approximately 90 °, it is possible to reliably avoid a situation in which the resistance value Rx of the pure resistance R of the measuring object 8 that is not originally zero ohms is a value close to zero ohms. can do.

  Further, according to the resistance measuring apparatus 1, the positive power supply voltage Vc and the negative power supply voltage supplied as operating voltages to the inverting circuit 11 of the synchronous rectification unit 4 (specifically, the operational amplifier 11c of the inverting circuit 11). By defining the absolute value of the power supply voltage (that is, negative power supply voltage) Vd of the above-defined polarity (negative polarity in this example) of Vd to a value smaller than the maximum amplitude of the AC signal S1, Without adding a special circuit, the amplitude on the negative polarity side (predetermined polarity) of the waveform in the second half cycle T2 of the synchronization signal St of the waveform of the synchronous rectification signal Sre is limited to a specified value Vd1 or less. can do.

  Moreover, according to this resistance measuring apparatus 1, the resistance value Rx of the pure resistance R of the measuring object 8 is calculated based on the A / D converter 5 that converts the synchronous rectified voltage Vr into the voltage data Dv, and the voltage data Dv. By providing the processing unit 6 to be displayed on the display unit 7, the display unit 7 can be constituted by a digital display such as an LCD, and the measured resistance value Rx can be displayed with a numerical value that can be easily confirmed. it can.

  In the resistance measuring apparatus 1, the inverting circuit 11 is disposed between the voltage detection unit 3 and the input terminal b of the switching circuit 12, so that the second half of the synchronization signal St in the waveform of the synchronous rectification signal Sre. Although the configuration in which the negative polarity amplitude of the waveform in the half cycle T2 is limited to a predetermined value Vd1 (the absolute value of the negative power supply voltage Vd) or less is employed, although not shown, the voltage detection is replaced with this configuration. A non-inverting circuit having an amplification factor of 1 is disposed between the unit 3 and the input terminal a of the switching circuit 12, and a positive power supply voltage and a negative power supply voltage supplied to the non-inverting circuit as operating voltages are arranged. Among them, the absolute value of the power supply voltage (that is, the negative power supply voltage Vd) having the above-mentioned predetermined polarity (in this example, negative polarity) is specified to a value lower than the maximum amplitude of the AC signal S1 (for example, the specified value Vd1). By doing so, as shown in FIG. A configuration in which the negative polarity amplitude of the waveform in the first half cycle T1 of the synchronization signal St in the waveform of the rectified signal Sre is limited to a predetermined value Vd1 (the absolute value of the negative power supply voltage Vd) or less can be employed. Even with this configuration, even when the phase difference between the two signals St and S1 is approximately 90 °, the resistance value Rx of the pure resistance R of the measurement target 8 that is not originally zero ohms is erroneously set to a value close to zero ohms. The situation to measure can be avoided reliably. In addition, in the following description, what has the same function as the component of resistance measuring apparatus 1 mentioned above attaches | subjects the same code | symbol, and abbreviate | omits the overlapping description.

  In the above example, of the positive power supply voltage Vc and the negative power supply voltage Vd supplied to the inverting circuit 11 and the non-inverting circuit, the power supply voltage (negative polarity in the present example) described above is negative. By defining the absolute value of the power supply voltage Vd) to a specified value (Vd1 in this example) smaller than the maximum amplitude of the AC signal S1, the first half cycle T1 of the synchronization signal St in the waveform of the synchronous rectification signal Sre or A configuration is adopted in which the amplitude of the predetermined polarity (negative polarity) of the waveform in the latter half cycle T2 is limited to a specified value Vd1 or less, but an inverting circuit like the synchronous rectification unit 4A shown in FIG. 11 is the same as the absolute value of the positive power supply voltage Vc (for example, the absolute value | Vc | of the positive power supply voltage Vc is the same as the absolute value of the positive power supply voltage Vc). Value, ie negative With the source voltage Vd = − | Vc |), the inverted AC signal S2 is output as it is as the inverted signal of the AC signal S1 from the inverter circuit 11, and the previously defined polarity (negative electrode) in the inverted AC signal S2 is output. Of the negative polarity side of the inverted AC signal S2 by using the voltage limiting circuit 14 (that is, a configuration that limits the waveform of the negative polarity side of the inverted AC signal S2 so as not to exceed the voltage value -Va). It can also be adopted.

  As an example, the voltage limiting circuit 14 includes a resistor 14a connected in series between the output of the inverting circuit 11 (the output terminal of the operational amplifier 11c) and the input terminal b of the switching circuit 12, as shown in FIG. The diode 14b whose cathode terminal is connected to the input terminal b, and the constant voltage source 14c (with the high potential side connected to the reference potential between the anode terminal of the diode 14b and the reference potential (ground potential) ( Voltage value Va). Here, the voltage value Va is defined as a value smaller than the maximum amplitude of the AC signal S1.

  With this configuration, the voltage limiting circuit 14 outputs the waveform on the positive polarity side in the inverted AC signal S2 as it is and ignores the amplitude of the waveform on the negative polarity side if the forward voltage of the diode 14b is ignored. The output can be limited to a value Va or less. For this reason, instead of the inverted AC signal S2, a new inverted AC signal S2a (see FIGS. 2 and 3) output from the voltage limiting circuit 14 is input to the input terminal b of the switching circuit 12, whereby this synchronous rectification is performed. According to the resistance measuring apparatus 1 including the unit 4A, although the circuit components are increased by the amount of the voltage limiting circuit 14, the absolute value of the negative power supply voltage Vd supplied to the inverting circuit 11 is changed to an alternating current with a relatively simple circuit configuration. In the same manner as the above-described configuration that defines the prescribed value Vd1 smaller than the maximum amplitude of the signal S1, the negative polarity amplitude of the waveform in the second half cycle T2 of the synchronous signal St of the waveforms of the synchronous rectification signal Sre is defined. It can be limited to a value Va or less. Therefore, according to the resistance measuring apparatus 1, the voltage limiting circuit 14 is added to the basic configuration of the synchronous rectification unit 4A, that is, the inverting circuit 11, the switching circuit 12, and the smoothing circuit 13, and the signal St and S1 are connected. Even when the phase difference is approximately 90 °, it is possible to reliably avoid a situation in which the resistance value Rx of the pure resistance R of the measuring object 8 that is not originally zero ohms is erroneously measured as a value close to zero ohms. .

  Further, in place of the configuration in which the voltage limiting circuit 14 is disposed on the inverted AC signal S2 side, although not illustrated, the voltage limiting circuit 14 is disposed on the AC signal S1 side, that is, before the input terminal a of the switching circuit 12 in FIG. You can also. In this configuration, a non-inverting circuit (a non-inverting circuit in which the absolute value of the negative power supply voltage Vd is defined to be smaller than the maximum amplitude of the AC signal S1) is provided between the voltage detection unit 3 and the input terminal a of the switching circuit 12. In the same manner as the above-described configuration, the voltage limiting circuit 14 outputs the waveform on the positive polarity side of the input AC signal S1 as it is, and defines the amplitude of the waveform on the negative polarity side of the AC signal S1. Output is limited to the value Va or less. Therefore, according to this configuration, as shown in FIG. 4, the negative-side amplitude of the waveform in the first half cycle T1 of the synchronization signal St in the waveform of the synchronous rectification signal Sre can be limited to a specified value Va or less. Therefore, the same operational effects as the above-described operational effects can be achieved.

  In the above example, the negative polarity side of the waveform in the first half cycle T1 of the synchronization signal St in the waveform of the synchronous rectification signal Sre or the waveform in one half cycle of the waveforms in the second half cycle T2. Is used, but the negative electrode of the waveform in each of the first half and the second half of the synchronous signal St in the waveform of the synchronous rectification signal Sre in the half periods T1 and T2 is employed. It is also possible to employ a configuration in which both the sex side amplitudes are limited to a specified value (Vd1 or Va) or less.

  For example, in the configuration of the synchronous rectification unit 4 shown in FIG. 1, this configuration is realized by adding the above-described non-inverting circuit before the input terminal “a” of the switching circuit 12 in addition to this configuration. can do. In addition to this configuration, the configuration shown in FIG. 5 can be realized by adding another voltage limiting circuit 14 before the input terminal a of the switching circuit 12 as described above. As another example, it can also be realized by providing a voltage limiting circuit 14 at the subsequent stage of the switching circuit 12 as in the synchronous rectification unit 4B shown in FIG.

  As described above, the negative-side amplitude of the waveform in the first half and the second half of the synchronous signal St in the waveform of the synchronous rectification signal Sre is limited to a predetermined value (Vd1 or Va) or less. By adopting, a comparison is made with the configuration in which only the amplitude on the negative polarity side of the waveform in one half cycle (T1 or T2) of the first half and the second half of the synchronization signal St is limited to this constant voltage or less. 7, since the integral value of the negative side portion can be further reduced, the synchronous rectification unit 4B performs synchronization in a state where the phase difference between the synchronization signal St and the AC signal S1 is approximately 90 °. The rectified voltage Vr can be output at a higher voltage. Therefore, according to this configuration, it is possible to more reliably avoid a situation in which the resistance value Rx of the pure resistance R of the measuring object 8 that is not originally zero ohms is erroneously measured as a value close to zero ohms.

  In the above example, the current supply unit 2 also functions as a signal output unit and outputs the synchronization signal St. However, this function is deleted from the current supply unit 2 and the synchronization signal St is deleted. It is also possible to adopt a configuration in which the signal output unit for outputting the signal is arranged separately from the current supply unit 2. Further, the current supply unit 2 generates an AC constant current I having a predetermined constant current value (known) and supplies it to the measurement object 8, and the processing unit 6 generates an AC voltage V generated across the measurement object 8. Although the structure which calculates resistance value Rx of the pure resistance R of the measuring object 8 based on the voltage data Dv which shows the voltage value of this is adopted, it replaces with this structure and the electric current supply part 2 is alternating current of an unknown electric current value. A current is generated and supplied to the measurement object 8, and the current value of the alternating current is measured by an ammeter provided separately. The processing unit 6 uses the current value measured by the ammeter and the voltage data Dv described above. A configuration in which the resistance value Rx of the pure resistance R of the measurement object 8 is calculated based on the above can also be adopted.

  In the above example, the waveform in the first half and / or second half period (T1 and / or T2) of the synchronization signal St in the waveform of the synchronous rectification signal Sre generated in the synchronous rectification unit 4 is specified in advance. Although a configuration is adopted in which the amplitude on the polarity (negative polarity) side is limited to a specified value (Vd1 or Va) smaller than the maximum amplitude of the AC signal S1 on the polarity side, although not shown, an inverting circuit 11 in which the absolute value of the positive polarity power supply voltage (that is, the positive power supply voltage) Vc is defined as a value (Vc1) smaller than the amplitude of the AC signal S1, or the diode 14b and the constant voltage source 14c ( By adopting a configuration in which the polarity of the voltage Va) is reversed, the first half of the synchronous signal St and / or the waveform of the synchronous rectification signal Sre generated in the synchronous rectification unit 4 are used. May adopt a configuration in which the amplitude on the predetermined polarity (positive polarity) side of the waveform in the latter half cycle (T1 and / or T2) is limited to a predetermined value (Vc1 or Va) or less. it can.

  In the resistance measuring apparatus 1, the synchronous rectified voltage Vr is converted into voltage data Dv by the A / D converter 5, and the processing unit 6 determines the resistance value of the pure resistance R of the measuring object 8 based on the voltage data Dv. A configuration in which Rx is calculated and displayed on the display unit 7 configured by an LCD or the like is employed, but by configuring the display unit 7 by an analog meter, as in the resistance measuring apparatus 1A illustrated in FIG. The display unit 7 can be directly connected to the synchronous rectification unit 4 so that the A / D conversion unit 5 and the processing unit 6 can be omitted. In this case, the analog meter is a voltmeter in which a pointer rotates by an angle corresponding to an input voltage on a display panel on which a scale is displayed, such as a movable coil voltmeter or a movable iron voltmeter. Shall. In addition, about 1 A of resistance measuring apparatuses, about the structure same as the resistance measuring apparatus 1, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  Also in this resistance measuring apparatus 1A, the synchronous rectified voltage Vr output from the synchronous rectification unit 4 is measured from the current supply unit 2 when the AC signal S1 is synchronized with the synchronous signal St as shown in FIG. 8 is coupled with the configuration in which the AC constant current I is supplied to the voltage 8, the voltage is proportional to the resistance value Rx of the pure resistance R of the measurement target 8. Therefore, the resistance value Rx of the pure resistance R of the measurement target 8 is configured by an analog meter. Therefore, the resistance value Rx of the pure resistance R of the measuring object 8 can be measured.

  Further, the influence of the inductance component included in the measurement object 8 on the pure resistance R increases, the phase of the AC signal S1 shifts from the synchronization signal St, and the phase difference between the two signals St and S1 becomes approximately 90 °. Even in this state, as shown in FIG. 3, the synchronous rectified voltage Vr is output as a voltage that is not zero volts, and therefore the display unit 7 configured with an analog meter does not indicate zero ohms. Therefore, even in this resistance measuring apparatus 1A, when the influence of the inductance component included in the measurement target 8 on the pure resistance R is large, the resistance value Rx of the pure resistance R of the measurement target 8 cannot be accurately measured. It is possible to avoid a situation in which the resistance value Rx of the pure resistance R of the measuring object 8 that is not zero ohms is measured as a value close to zero ohms due to the influence of the inductance component.

  Also in this resistance measuring apparatus 1A, it goes without saying that instead of the synchronous rectification unit 4, a synchronous rectification unit having another configuration described above such as the synchronous rectification units 4A and 4B may be used.

DESCRIPTION OF SYMBOLS 1,1A Resistance measuring apparatus 2 Current supply part 3 Voltage detection part 4 Synchronous rectification part 5 A / D conversion part 6 Processing part 8 Measuring object 13 Smoothing circuit 14 Voltage limiting circuit I AC constant current R Pure resistance S1 AC signal S2 Inversion AC Signal Sre Synchronous rectification signal St Synchronization signal Va, Vc1, Vd1 Specified value Vr Synchronous rectification voltage

Claims (6)

A current supply unit for supplying an alternating current to the measurement target;
A signal output unit that outputs a synchronization signal having the same frequency and the same phase as the alternating current; and
A voltage detection unit that detects and outputs an AC signal generated between both ends of the measurement target when the AC current is flowing to the measurement target;
The synchronous rectified signal is generated by inputting the synchronous signal and the alternating current signal, generating the synchronous rectified signal by inverting and outputting the alternating current signal every half cycle of the synchronous signal, and smoothing the synchronous rectified signal. A synchronous rectifier that outputs as
A resistance measuring device including a display unit that displays the pure resistance of the measurement object based on the synchronous rectified voltage,
The synchronous rectification unit calculates a predetermined polarity side amplitude of a waveform in at least one of the first half cycle and the second half cycle of the synchronous signal of the waveform of the synchronous rectification signal. A resistance measuring device that restricts the value to a specified value smaller than the maximum amplitude of the AC signal.   The resistance measuring apparatus according to claim 1, wherein the display unit includes an analog meter that drives a pointer based on the synchronous rectified voltage on the display panel on which a scale is displayed to indicate the pure resistance. An A / D converter that converts the synchronous rectified voltage into voltage data;
A processing unit that calculates the pure resistance of the measurement target based on the voltage value of the AC signal represented by the voltage data and the current value of the AC current, and displays the calculated pure resistance on the display unit; The resistance measuring device according to claim 1, comprising:   The synchronous rectification unit inverts the input AC signal and outputs it as an inverted AC signal, and alternately outputs the input AC signal and the inverted AC signal every half cycle of the synchronization signal. A switching circuit for generating the synchronous rectification signal; and a smoothing circuit for generating the synchronous rectification voltage by smoothing the synchronous rectification signal, wherein an absolute value of the power supply voltage on the polarity side defined in the inverting circuit is The resistance measuring device according to claim 1, wherein the resistance measuring device is defined by the specified value.   The synchronous rectifying unit inverts the input AC signal and outputs the inverted AC signal as an inverted AC signal, and the predetermined polarity side amplitude of at least one of the AC signal and the inverted AC signal. The voltage limiting circuit that outputs the limited signal below the specified value, the one signal output from the voltage limiting circuit, and the other of the AC signal and the inverted AC signal for each half cycle of the synchronization signal. The switching circuit which produces | generates the said synchronous rectification signal by outputting alternately, The smoothing circuit which smoothes the said synchronous rectification signal and produces | generates the said synchronous rectification voltage is provided in any one of Claim 1 to 3 Resistance measuring device.   The synchronous rectification unit inverts the input AC signal and outputs it as an inverted AC signal, and alternately outputs the input AC signal and the inverted AC signal every half cycle of the synchronization signal. The switching circuit for generating the synchronous rectification signal, the voltage limiting circuit for limiting and outputting the amplitude of the predetermined polarity side in the synchronous rectification signal to be equal to or less than the predetermined value, and the output from the voltage limiting circuit The resistance measuring apparatus according to claim 1, further comprising a smoothing circuit that smoothes a synchronous rectification signal and generates the synchronous rectification voltage.

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