JP2009216618A - Impedance measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impedance measuring device capable of reducing an influence of a noise. <P>SOLUTION: A resistance measuring device 1 includes a voltage injection part 51 for injecting an AC voltage Vx for inspection into a measuring object circuit 5, a current measuring part 52 for measuring an AC current Ix flowing in the measuring object circuit 5 caused by injection of the AC voltage Vx for inspection, and a processing part 46 for calculating a resistance value Rx of the measuring object circuit 5 based on the injected AC voltage Vx for inspection and the measured AC current Ix. The voltage injection part 51 is constituted so that the AC voltage Vx for inspection having each frequency f1, f2 can be injected into the measuring object circuit 5, and the processing part 46 calculates resistance values Rx1, Rx2 relative to each frequency f1, f2 of the AC voltage Vx for inspection, and adopts the largest resistance value (larger one) between the calculated resistance values Rx1, Rx2 as the resistance value Rx of the measuring object circuit 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an impedance measuring apparatus that measures the impedance of a circuit to be measured.

As this type of impedance measuring apparatus, a resistance measuring apparatus disclosed in Patent Document 1 below is known. This resistance measuring device is a transformer for injection that clips a connection conductor of a measurement circuit network and injects into the measurement circuit a current of a second frequency that can be distinguished from the current of the first frequency flowing in the measurement circuit network (measurement object). A detection transformer for detecting the two types of current flowing in the measurement circuit by clipping the connection conductor, a frequency selection circuit for extracting a second frequency component from the output of the detection transformer, Display means for displaying the output of the frequency selection circuit, and the injection transformer further includes an injection coil for receiving an output voltage of the oscillator and injecting a current of the second frequency into the measurement network, and a feedback coil. The feedback coil is configured to vary the voltage supplied to the injection coil so that the voltage induced in the feedback coil is controlled to a constant value. In this resistance measuring device, the injection voltage obtained by dividing the voltage induced in the feedback coil by the ratio of the number of windings of the feedback coil to the number of connecting conductors (number of clips, one) of the measurement network is also constant. Therefore, the resistance value of the resistor connected to the detection transformer is detected by detecting the voltage generated in the resistor connected to the detection transformer due to the current flowing in the detection transformer. Based on the voltage generated in this resistor, the voltage generated in the feedback coil, the number of turns of the injection transformer and the number of turns of the detection transformer, the value of the resistance element connected to the measurement network (measured resistance) is measured. It is possible to do.
Japanese Examined Patent Publication No. 2-7031 (page 1-4, Fig. 2)

  However, the above resistance measuring apparatus has the following problems. That is, in this resistance measuring device, one second frequency current that can be distinguished from the first frequency current is injected into the measurement circuit network. However, in this resistance measurement device, when noise having the same frequency as the second frequency is superimposed on the current flowing through the measurement circuit network, the resistance element connected to the measurement circuit network is accurately set under the influence of the noise. There is a problem that it cannot be measured.

  The present invention has been made to solve such problems, and it is a main object of the present invention to provide an impedance measuring apparatus capable of reducing the influence of noise.

  In order to achieve the above object, the impedance measuring apparatus according to claim 1 is a voltage injection unit that injects an AC voltage for inspection into a circuit to be measured, and an AC that flows through the circuit under measurement due to the injection of the AC voltage for inspection. An impedance measuring device comprising: a current measuring unit that measures current; and a processing unit that calculates the impedance of the circuit to be measured based on the injected AC voltage for inspection and the measured AC current, The voltage injection unit is configured to be able to inject a plurality of the inspection AC voltages having different frequencies into the circuit to be measured, and the processing unit calculates the impedance for each frequency of the inspection AC voltage, and calculates the impedance The maximum impedance among the plurality of impedances is set as the impedance of the circuit to be measured.

  The impedance measuring device according to claim 2 is the impedance measuring device according to claim 1, wherein the current measuring unit measures the alternating current by synchronous detection using a detection signal having the same frequency as the alternating voltage for inspection. To do.

  The impedance measuring device according to claim 3 is the impedance measuring device according to claim 1 or 2, wherein the processing unit calculates and averages a plurality of the impedances for each frequency of the AC voltage for inspection. The maximum average value among the plurality of average values is set as the impedance of the circuit to be measured.

  In the impedance measuring apparatus according to claim 1, the voltage injection unit is configured to be able to inject a plurality of test AC voltages having different frequencies into the measurement target circuit, and the processing unit includes a measurement target circuit for each frequency of the test AC voltage. The impedance is calculated, and the maximum impedance among the calculated impedances is measured as the impedance of the circuit to be measured. Therefore, according to this resistance measuring apparatus, even when noise (noise current) is flowing through the circuit to be measured, a test AC voltage having a frequency less affected by noise is injected into the circuit to be measured. By measuring the calculated impedance as the final impedance of the circuit to be measured, the influence of noise can be reduced. As a result, impedance measurement accuracy can be sufficiently improved.

  According to the impedance measuring apparatus of claim 2, the frequency of the alternating current is changed by the current measuring unit measuring the alternating current by the synchronous detection using the detection signal having the same frequency as the AC voltage for inspection. Even at times, alternating current can be reliably detected.

  According to the impedance measuring apparatus of claim 3, when calculating the resistance of the impedance of the measurement target circuit for each frequency of the test AC voltage, the processing unit calculates and averages the impedance multiple times for each frequency, By using the maximum average value among a plurality of average values (average values of each frequency) as the impedance of the circuit to be measured, the influence of measurement errors caused by A / D conversion and D / A conversion can be reduced. As a result, impedance measurement accuracy can be further improved.

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

  Initially, the structure of the resistance measuring apparatus 1 which is an example of the impedance measuring apparatus which concerns on this invention is demonstrated with reference to drawings.

  A resistance measuring device 1 shown in FIG. 1 includes a clamp unit 2 and a device main body unit 4 connected to the clamp unit 2 via a cable 3. The impedance of the measurement target circuit 5 (in this example, a resistance (loop resistance) The resistance value Rx) can be measured.

  As shown in FIG. 1, the clamp unit 2 includes an injection clamp unit 11, a detection clamp unit 21, and a housing 31. As an example, in this example, the injection clamp unit 11 includes a first annular core 12 divided into two parts, and a first winding 13 (known number of turns: N1) wound around the first annular core 12. Have. Moreover, the detection clamp part 21 has the 2nd cyclic | annular core 22 divided | segmented into two, and the 2nd coil | winding 23 (known number of turns: N2) wound by the 2nd cyclic | annular core 22. FIG. The injection clamp part 11 and the detection clamp part 21 are housed together in a clamp-type resin housing 31 whose tip can be freely opened and closed. The two annular cores 22 are configured to open and close simultaneously. With this configuration, each of the first annular core 12 and the second annular core 22 that are in the open state can be obtained by introducing the wiring 5a that constitutes a part of the circuit to be measured 5 inside the housing 31 in the open state. The wiring 5a is also introduced inside, and in this state, the housing 31 is closed, so that the wiring 5a is simultaneously clamped by the closed first annular core 12 and the second annular core 22, that is, the clamp The wiring 2a is clamped by the part 2. In this case, the wiring 5 a functions as a one-turn winding in the first annular core 12 and the second annular core 22.

  As shown in FIG. 1, the apparatus body 4 includes a D / A converter 41, a power amplifier 42, a current detector 43, a detector 44, an A / D converter 45, a processor 46, and an output unit 47. ing. In this case, the D / A conversion unit 41, the power amplification unit 42, and the injection clamp unit 11 constitute the voltage injection unit 51 in the present invention, and the detection clamp unit 21, the current detection unit 43, the detection unit 44, and the A / D conversion unit. 45 constitutes the current measuring unit 52 in the present invention.

  The D / A converter 41 converts the AC waveform data Dv output from the processing unit 46 into an AC voltage Va at a predetermined conversion rate and outputs the AC voltage Va. The power amplifying unit 42 amplifies the AC voltage Va with a predetermined amplification factor to generate an AC voltage V1 having a predetermined amplitude, and the generated AC voltage V1 is applied to the first winding 13 of the injection clamp unit 11. Apply. As a result, the test AC voltage Vx is injected into the measurement target circuit 5 via the injection clamp unit 11. In this case, the inspection AC voltage Vx injected into the measurement target circuit 5 is obtained by dividing the AC voltage V1 by the number of turns N1 because the wiring 5a functions as a one-turn winding in the first annular core 12 in this example. The voltage value obtained in this way (Vx = V1 / N1).

  Since the wiring 5a functions as a one-turn winding in the second annular core 22, the detection clamp unit 21 detects the alternating current Ix flowing through the measurement target circuit 5, and detects the detection current I1 ( = Ix / N2) is output. The current detection unit 43 converts the detection current I1 into an AC voltage Vb and outputs it. The detection unit 44 synchronously detects the AC voltage Vb using the detection signal Sd (clock signal synchronized with the AC voltage Va) output from the processing unit 46, and outputs the AC voltage Vc having the same frequency as the AC voltage Va. Then, the A / D converter 45 converts the AC voltage Vc into digital data and outputs it as current data Di. Therefore, the current data Di output from the A / D converter 45 is data representing the detected current I1.

  The processing unit 46 includes a CPU and a memory (both not shown), and performs an impedance measurement process (in this example, a resistance measurement process). The output unit 47 includes a monitor device as an example, and displays the result of the resistance measurement process.

  Next, the resistance measurement process 100 by the resistance measurement apparatus 1 will be described with reference to FIG.

  In the resistance measurement process 100, the processing unit 46 first executes an injection process for injecting the test AC voltage Vx having the frequency f1 into the measurement target circuit 5 (step 101). Specifically, in this injection process, the processing unit 46 starts outputting the AC waveform data Dv for generating the AC voltage Va having the frequency f1 to the voltage injection unit 51. As a result, in the voltage injection unit 51, the D / A conversion unit 41 converts the AC waveform data Dv into an AC voltage (analog signal) Va and outputs it, and the power amplification unit 42 converts the AC voltage Va into the AC voltage. Amplified to V 1 and applied to the first winding 13 of the injection clamp unit 11. As a result, the inspection AC voltage Vx (frequency f1) is injected from the injection clamp unit 11 into the measurement target circuit 5. For this reason, the alternating current Ix of the frequency f1 flows through the measurement target circuit 5 due to the injection of the inspection AC voltage Vx. Further, simultaneously with the start of output of the AC waveform data Dv, the processing unit 46 also starts outputting the detection signal Sd whose frequency is defined as f1 to the detection unit 44.

  In a state in which the inspection AC voltage Vx having the frequency f1 is injected into the measurement target circuit 5, the current measurement unit 52 performs a process of detecting the AC current Ix and generating current data Di. Specifically, in the current measurement unit 52, the detection clamp unit 21 detects the alternating current Ix flowing through the measurement target circuit 5, outputs the detection current I 1 from the second winding 23, and the current detection unit 43 The detection current I1 is converted into an alternating voltage Vb and output. Further, the detection unit 44 synchronously detects the AC voltage Vb using the detection signal Sd, and outputs the AC voltage Vc composed of the same frequency component as the AC voltage Va (component of the frequency f1) (that is, the frequency The A / D converter 45 converts the AC voltage Vc into digital data and outputs it as current data Di to the processing unit 46.

  Next, the processing unit 46 executes a calculation process for calculating the resistance value Rx1 of the measurement target circuit 5 when the frequency is f1 (step 102). Specifically, in this calculation process, the processing unit 46 calculates the test AC voltage Vx based on the amplitude of the AC voltage V1 and the number of turns (N1) of the first winding 13, and specifies the current data Di. The alternating current Ix is calculated based on the detected current I1 and the number of turns (N2) of the second winding 23. Further, the processing unit 46 calculates the resistance value Rx1 of the measurement target circuit 5 when the frequency of the AC voltage Vx is f1 based on the calculated AC voltage Vx for inspection and AC current Ix, and the calculated resistance value. Rx1 is stored in the memory in association with the frequency f1. When calculating the resistance value Rx1, the processing unit 46 calculates the resistance value Rx1 a plurality of times and calculates an average of these values (a moving average as an example) to obtain a final resistance value Rx1.

  Subsequently, the processing unit 46 performs an injection process of injecting the test AC voltage Vx having a frequency f2 different from the frequency f1 into the measurement target circuit 5 (step 103). Specifically, in this injection process, the processing unit 46 starts outputting the AC waveform data Dv for generating the AC voltage Va having the frequency f2 to the D / A conversion unit 41. Accordingly, the voltage injection unit 51 injects the inspection AC voltage Vx (frequency f2) into the measurement target circuit 5 in the same manner as when the frequency is f1. For this reason, the alternating current Ix of the frequency f2 flows through the measurement target circuit 5 due to the injection of the inspection AC voltage Vx. The processing unit 46 also starts outputting the detection signal Sd whose frequency is defined as f2 simultaneously with the start of the output of the AC waveform data Dv.

  In a state where the inspection AC voltage Vx having the frequency f2 is injected into the measurement target circuit 5, the current measurement unit 52 performs the AC current Ix (frequency f2) flowing in the measurement target circuit 5 in the same manner as when the frequency is f1. ) And current data Di are generated and output to the processing unit 46.

  Subsequently, the processing unit 46 executes a calculation process for calculating the resistance value Rx2 of the measurement target circuit 5 when the frequency is f2 (step 104). Specifically, in this calculation process, the processing unit 46 calculates the test AC voltage Vx based on the amplitude of the AC voltage V1 and the number of turns (N1) of the first winding 13, and specifies the current data Di. The alternating current Ix is calculated based on the detected current I1 and the number of turns (N2) of the second winding 23. Further, the processing unit 46 calculates the resistance value Rx2 of the measurement target circuit 5 when the frequency of the AC voltage Vx is f2 based on the calculated AC voltage Vx for inspection and the AC current Ix, and calculates the calculated resistance value. Rx2 is stored in the memory in association with the frequency f2. Also in calculating the resistance value Rx2, the processing unit 46 calculates the resistance value Rx2 a plurality of times and calculates an average of these (as an example, a moving average) to obtain a final resistance value Rx2.

  Next, the processing unit 46 executes a process for specifying the resistance value Rx (step 105). In this specific process, the processing unit 46 reads out the resistance values Rx1 and Rx2 at the respective frequencies f1 and f2 stored in the memory and compares the resistance values Rx1 and Rx2 to determine the larger value ( The maximum resistance value) is specified as the final resistance value Rx of the circuit to be measured 5 and stored in the memory. In this case, when noise (noise current) having the same frequency as one of the frequencies f1 and f2 is flowing in the measurement target circuit 5, the test AC voltage Vx having the one frequency is caused by the noise. The measurement accuracy of the resistance value Rx measured when applying is greatly reduced. However, the resistance value Rx calculated (measured) when the test AC voltage Vx having one frequency is applied is the test AC voltage Vx having the other frequency (frequency different from the frequency of the noise component). It is always calculated as a value smaller than the resistance value Rx calculated (measured). This is because the detection current I1 output from the detection clamp unit 21 is increased by the amount of superimposed noise, and as a result, the resistance value Rx of the measurement target circuit 5 is calculated as a value smaller than the actual value. Because. Therefore, by specifying the resistance value Rx having a large value as the resistance value Rx of the measurement target circuit 5, the resistance value Rx at a frequency with less noise influence is specified as the resistance value Rx of the measurement target circuit 5. be able to. Finally, the processing unit 46 causes the output unit 47 to output the identified resistance value Rx (step 106). Thereby, the resistance measurement process is completed.

  As described above, in the resistance measuring apparatus 1, the voltage injection unit 51 is configured so that the test AC voltage Vx having different frequencies f1 and f2 can be injected into the measurement target circuit 5, and the processing unit 46 is provided for each of the frequencies f1 and f2. The resistance values Rx1 and Rx2 of the measurement target circuit 5 are calculated, and the larger one of the calculated resistance values Rx1 and Rx2 is measured as the final resistance value Rx of the measurement target circuit 5. Therefore, according to the resistance measuring apparatus 1, even when noise (noise current) is flowing in the measurement target circuit 5, the test AC voltage Vx having a frequency less affected by noise is supplied to the measurement target circuit 5. By measuring the resistance value Rx (one of Rx1 and Rx2) calculated at the time of injection as the final resistance value Rx of the measurement target circuit 5, the influence of noise can be reduced. As a result, the resistance value Rx Measurement accuracy can be sufficiently improved.

  Further, according to the resistance measuring apparatus 1, the detection unit 44 detects (measures) the AC voltage Vc indicating the AC current Ix by synchronous detection using the detection signal Sd having the same frequency as the AC voltage Vx for inspection. Even when the frequency of the alternating current Ix is changed, the alternating voltage Vc indicating the alternating current Ix can be reliably detected.

  Further, according to the resistance measuring apparatus 1, when calculating the resistances Rx1 and Rx2 of the measurement target circuit 5 at the respective frequencies f1 and f2, the resistance value Rx is calculated a plurality of times for each of the frequencies f1 and f2 and averaged. As a result, it is possible to reduce the influence of measurement errors caused by A / D conversion, D / A conversion, and the like. As a result, the measurement accuracy of the resistance value Rx can be further improved.

  In addition, this invention is not limited to said structure. For example, in the above configuration, the resistance values Rx1 and Rx2 are calculated and averaged for each of the frequencies f1 and f2 of the AC voltage Vx for inspection, and the maximum average value among the plurality of average values is calculated by Although the resistance value Rx is used, the resistance values Rx1 and Rx2 are calculated once for each of the frequencies f1 and f2, and the larger of the resistance values Rx1 and Rx2 can be used as the resistance value Rx of the measurement target circuit 5. In addition, three or more types of test AC voltages Vx having different frequencies are injected into the measurement target circuit 5, and the resistance value Rx at each frequency is measured, and the maximum of them is finally determined as the measurement target circuit. A configuration in which the resistance value Rx of 5 is measured may be employed. According to this configuration, it is possible to increase the probability that the frequency of the noise flowing in the measurement target circuit 5 is different from the frequency of the AC voltage Vx for inspection, and as a result, the influence of noise can be further reduced. The measurement accuracy of the value Rx can be further improved. Further, although an example of executing the resistance measurement process has been described as an example of the impedance measurement process, it is needless to say that the present invention can be applied to a configuration in which the impedance of the circuit to be measured 5 is measured.

1 is a configuration diagram showing a configuration of a resistance measuring device 1. FIG. 4 is a flowchart for explaining resistance measurement processing by the resistance measuring apparatus 1;

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resistance measuring apparatus 5 Circuit to be measured 44 Detection part 46 Processing part 51 Voltage injection part 52 Current measurement part Ix AC current Rx Resistance Vx AC voltage for inspection

Claims (3)

A voltage injection unit for injecting a test AC voltage into the measurement target circuit; a current measurement unit for measuring an AC current flowing through the measurement target circuit due to the injection of the test AC voltage; and the injected test AC An impedance measuring device comprising: a processing unit that calculates an impedance of the circuit to be measured based on a voltage and the measured alternating current;
The voltage injection unit is configured to be able to inject a plurality of the inspection AC voltages having different frequencies into the measurement target circuit,
The processing unit calculates the impedance for each frequency of the AC voltage for inspection, and uses the maximum impedance among the calculated plurality of impedances as the impedance of the measurement target circuit.   The impedance measuring apparatus according to claim 1, wherein the current measuring unit measures the AC current by synchronous detection using a detection signal having the same frequency as the AC voltage for inspection.   The processing unit calculates and averages a plurality of the impedances for each frequency of the AC voltage for inspection, and sets the maximum average value among the plurality of average values as the impedance of the circuit to be measured. 2. The impedance measuring device according to 2.

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