JP4817987B2 - Impedance measuring device - Google Patents

Description

  The present invention relates to an impedance measuring apparatus for measuring the impedance of a measurement object.

As this type of impedance measuring apparatus, the applicant has developed an impedance measuring apparatus disclosed in Japanese Patent Application Laid-Open No. 11-295362. This impedance measuring device differentially calculates the voltage between both ends of an AC constant current source for supplying an AC constant current to the measurement object via the current supply probe and the measurement object input via the voltage detection probe. A differential amplifier circuit for amplifying, a synchronous detector circuit for synchronously detecting the output voltage of the differential amplifier circuit based on a synchronous signal synchronized with an AC constant current, and calculating an impedance based on the output voltage of the synchronous detector circuit A CPU and differential amplifier circuit saturation detection means for detecting saturation of the output voltage of the differential amplifier circuit are provided. In this impedance measuring apparatus, when the output voltage of the differential amplifier circuit is saturated and distorted, the differential amplifier circuit saturation detection means detects and outputs it, and the CPU detects the differential amplifier circuit saturation detection means. Based on this detection result, avoiding erroneous measurement by notifying that the measurement object is not normally measured due to the large impedance of the measurement object or stopping the measurement. Is possible.
Japanese Patent Laid-Open No. 11-295362 (page 3-4, FIG. 1)

  However, the impedance measuring apparatus already developed by the applicant has the following points to be improved. That is, when the output voltage of the differential amplifier circuit is saturated and distorted, in addition to the example disclosed in Patent Document 1, for example, a non-linear element such as a diode is used as a measurement object, and the measurement object is appropriate. When a large inspection signal is not supplied (specifically, when an AC signal having an excessive amplitude is supplied as the inspection signal). In this case, by controlling the inspection signal supplied to the measurement target object to an appropriate voltage, the measurement of the impedance of the measurement target object can be continued. Since the voltage value cannot be controlled, the impedance measurement cannot be continued, and improvement of this point is desired.

  The present invention has been made in view of such improvements, and an impedance measuring apparatus capable of measuring an accurate impedance by avoiding an erroneous measurement when distortion occurs in a current or voltage detected from a measurement object. The main purpose is to provide.

In order to achieve the above object, the impedance measuring apparatus according to claim 1 includes a signal supply unit that supplies an inspection signal to the measurement object, an alternating current that flows through the measurement object when the inspection signal is supplied, and the alternating current. A measurement unit that measures the impedance of the measurement object based on a voltage between both ends generated at both ends of the measurement object due to supply of current, and the signal supply unit is a DC signal as the inspection signal. Is supplied to the object to be measured, and the measurement unit detects distortion of the inspection signal included in at least one of the AC current and the voltage between both ends, and the distortion is a specified value. A distortion detection unit that outputs a detection signal at the time described above, and when the detection signal is output from the distortion detection unit, the signal supply unit is controlled to control the voltage value of the DC signal. And a control unit for increasing either the fine current value.

Impedance measuring apparatus according to claim 2, wherein, in the impedance measuring apparatus according to claim 1 Symbol placement, the distortion detection unit detects a distortion of the test signal by the Fourier transform operation.

Impedance measuring apparatus according to claim 3, wherein, in the impedance measuring apparatus according to claim 1 Symbol placement, the strain detection unit is configured with a band elimination filter, the test signal which passes through the band-elimination filter A distortion of the inspection signal is detected based on the harmonic component.

In the impedance measuring device 請 Motomeko 1 wherein, in a state in which the signal supply unit is supplied to the measurement object an alternating signal as a test signal, between the alternating current and its both end distortion detector is flowing through the measured object Detects distortion of the inspection signal included in at least one of the voltages and outputs a detection signal when the distortion is equal to or greater than a specified value. The control unit outputs a signal while the detection signal is output from the distortion detection unit. The supply unit is controlled to increase either the voltage value or the current value of the DC voltage. Therefore, according to this impedance measuring apparatus, even when the voltage value of the AC signal is equal to or higher than a predetermined value when the measurement object is a nonlinear element such as a diode, the alternating current flowing through the measurement object and its Impedance measurement can be continued while automatically increasing either the voltage value or the current value of the DC signal until the distortion of the inspection signal contained in each waveform of the voltage across the terminal falls below the specified value. Therefore, it is possible to accurately measure the impedance while avoiding erroneous measurement.

According to the impedance measuring apparatus of the second aspect , the distortion detector can detect the distortion of the inspection signal accurately by detecting the distortion of the inspection signal by Fourier transform calculation.

According to the impedance measuring apparatus of claim 3 , the distortion detector calculates the distortion with a simple configuration by detecting the distortion of the inspection signal based on the harmonic component of the inspection signal that has passed through the band elimination filter. can do.

Hereinafter, with reference to the accompanying drawings, illustrating the best mode impedance measuring device.

  First, the configuration of the impedance measuring apparatus 1 will be described with reference to the drawings.

  As shown in FIG. 1, the impedance measuring apparatus 1 includes a signal supply unit 2, a current detection unit 3, a voltage detection unit 4, a distortion detection unit 5, a calculation control unit 6, and a display unit 7, and is a measurement target. The impedance Z of the body 11 is measured. The signal supply unit 2 generates an AC signal Vs that is a sine wave signal as an inspection signal. The signal supply unit 2 is configured to be connectable to one end side of the measurement target body 11 via a current supply probe 12 (hereinafter also referred to as “probe 12”), and the generated AC signal Vs is supplied to the measurement target body 11. Supply. Further, the signal supply unit 2 has a function of changing the voltage value (amplitude value) of the AC signal Vs. In this case, the signal supply unit 2 changes the voltage value of the AC signal Vs according to the control of the arithmetic control unit 6.

  The current detection unit 3 includes a current / voltage converter (hereinafter also referred to as “I / V converter”) 31, a filter 32, and an A / D converter 33, and includes a voltage detection unit 4, a distortion detection unit 5, and arithmetic control. The measurement part ME in this invention is comprised with the part 6. FIG. Further, the current detection unit 3 is configured to be connectable to the other end side of the measurement target body 11 via a current detection probe 13 (hereinafter also referred to as “probe 13”), and an alternating current I 1 flowing through the measurement target body 11. Is detected. Specifically, the voltage value of the alternating current I1 (current flowing through the measurement object 11) input by the I / V converter 31 via the probe 13 changes in proportion to the voltage value of the alternating current I1. Current-voltage converted to voltage signal S1 is output. The filter 32 is configured as a low-pass filter, removes a noise component contained in the input voltage signal S1, and outputs it as a voltage signal S2. The A / D converter 33 outputs the digital data Di indicating the voltage value of the voltage signal S2 by sampling the input voltage signal S2 at a predetermined sampling period.

  The voltage detection unit 4 includes a differential amplifier 41, a filter 42, and an A / D converter 43. Further, the voltage detection unit 4 is configured to be connectable to each end of the measurement object 11 via a pair of voltage detection probes 14 and 15 (hereinafter also referred to as “probes 14 and 15”), and an alternating current I1. The voltage (the voltage between both ends in the present invention) V1 generated between both ends of the measurement object 11 due to the supply of is detected. Specifically, the differential amplifier 41 amplifies the voltage V1 detected via each probe 14, 15 and outputs it as a voltage signal S3. The filter 42 is configured as a low-pass filter, removes a noise component contained in the input voltage signal S3, and outputs it as a voltage signal S4. The A / D converter 43 outputs the digital data Dv indicating the voltage value of the voltage signal S4 by sampling the input voltage signal S4 at a predetermined sampling period.

  The distortion detector 5 is configured by a DSP as an example, and detects distortion occurring in at least one of the waveforms of the input voltage signal S2 and voltage signal S4. The distortion detector 5 outputs a detection signal S5 when the detected distortion is equal to or greater than a preset specified value. In this example, the distortion detection unit 5 is, for example, the ratio of the harmonic component to the fundamental component of each waveform (AC signal Vs) for the voltage signals S2 and S4 (the distortion in the present invention. Is calculated by FFT (fast Fourier transform as an example of Fourier transform in the present invention), and the detection signal S5 is output when this ratio is equal to or greater than a specified value. Note that the distortion rate can also be calculated by DFT (Discrete Fourier Transform) calculation instead of FFT calculation. In this way, the distortion rate can be accurately calculated by using the Fourier transform operation.

  Further, the distortion detection unit 5 can be configured by including a band elimination filter. In this configuration, the distortion detector 5 detects the distortion rate of the voltage signals S2 and S4 based on the harmonic components of the voltage signals S2 and S4 that have passed through the band elimination filter. Specifically, the distortion detector 5 passes the harmonic component of each waveform (AC signal Vs) for the voltage signals S2 and S4 through the band elimination filter, and each waveform (AC signal) for the voltage signals S2 and S4. The ratio of the passed harmonic component to the fundamental wave component of Vs) is calculated, and the detection signal S5 is output when the distortion rate is equal to or greater than a specified value. In this way, by using the band elimination filter, the distortion rate can be calculated with a simple configuration. Further, similarly to the above-described conventional example, it is possible to employ a configuration in which it is detected whether or not the signal waveform is saturated and the detection signal S5 is output when the signal waveform is saturated.

  The arithmetic control unit 6 includes a CPU and an internal memory (both not shown), and is configured as a control unit in the present invention to display impedance calculation processing based on the digital data Di and the digital data Dv, and the calculated impedance and the like. Display processing to be displayed on the unit 7 is executed. In addition, when the detection signal S5 is input, the arithmetic control unit 6 outputs the control signal S6 and executes operation control of the signal supply unit 2. The display unit 7 includes an LCD or the like, and displays the calculated impedance Z and the like under the control of the arithmetic control unit 6.

  Next, the measurement operation of the impedance measuring apparatus 1 will be described. In addition, the example which measures the impedance of a diode as the measuring object 11 is demonstrated.

  First, each probe 12, 13, 14, 15 is connected to the measurement object 11. Next, measurement by the impedance measuring device 1 is started in that state. At this time, the signal supply unit 2, the current detection unit 3, the voltage detection unit 4, the distortion detection unit 5, and the calculation control unit 6 start their respective operations. The signal supply unit 2 generates and outputs an AC signal Vs with a preset initial voltage value. As a result, the AC signal Vs is supplied to the measurement object 11 via the probe 12, and thus the alternating current I <b> 1 starts to flow through the measurement object 11.

  In this state, the current detector 3 converts the alternating current I1 input by the I / V converter 31 via the probe 13 into the voltage signal S1 and outputs the voltage signal S1, and the filter 32 includes noise included in the voltage signal S1. The component is removed and output as a voltage signal S2, and the A / D converter 33 converts the voltage signal S2 into digital data Di and outputs it. In the voltage detector 4, the differential amplifier 41 amplifies the voltage V1 detected via the probes 14 and 15 and outputs it as a voltage signal S3, and the filter 42 removes the noise component contained in the voltage signal S3. The A / D converter 43 converts the voltage signal S4 into digital data Dv and outputs the voltage signal S4. Further, the distortion detection unit 5 detects distortion of each waveform of the voltage signals S2 and S4, and detects whether or not the detected distortion rate is equal to or greater than a specified value. The arithmetic control unit 6 executes impedance calculation processing based on the digital data Di and the digital data Dv to calculate the impedance Z, executes display processing, and causes the display unit 7 to display the calculated impedance Z.

  By the way, in this example, since the measurement object 11 is a diode of a nonlinear element, when the AC signal Vs having an appropriate voltage value (amplitude value) is not supplied from the signal supply unit 2 to the measurement object 11, In some cases, distortion of a specified value or more occurs in at least one of the alternating current I1 and the voltage V1, and the correct impedance Z cannot be measured. In this case, the distortion detector 5 detects that the distortion rate of the detected waveform is equal to or greater than a specified value, and outputs a detection signal S5. When the detection signal S5 is input, the arithmetic control unit 6 may cause an erroneous measurement on the display unit 7 during display processing while the detection signal S5 is being input (until the input of the detection signal S5 is stopped). In addition, the control signal S6 is output to control the signal supply unit 2 to gradually decrease the voltage value of the AC signal Vs. In this case, the current value of the AC signal Vs may be gradually decreased by outputting the control signal S6 and controlling the signal supply unit 2.

  In this case, when the voltage value of the supplied AC signal Vs is equal to or lower than a predetermined voltage value (which varies depending on the diode, for example, 600 mV or less), the diode as the measurement object 11 is forward and reverse in terms of DC. While any of the directions is in a non-conductive state, it is in a bidirectional conductive state in terms of alternating current, and exhibits a linear characteristic in which the current changes substantially linearly with respect to the alternating current signal Vs. For this reason, in this state, the waveform distortion of the alternating current I1 and the voltage V1 is reduced, and the waveform distortion rates of the voltage signals S2 and S4 are also less than the specified value. As a result, the distortion detector 5 outputs the detection signal S5. Stop. Accordingly, the arithmetic control unit 6 stops displaying the possibility of erroneous measurement while continuing to display the calculated impedance Z in the display process.

  As described above, in this impedance measuring apparatus 1, the distortion detection unit 5 is flowing through the measurement target body 11 while the signal supply unit 2 is supplying the AC signal Vs to the measurement target body 11 as an inspection signal. The distortion of the AC signal Ss included in each waveform of the current I1 and the voltage V1 between both ends thereof is detected, and the detection signal S5 is output when the distortion rate is equal to or greater than a specified value. While the detection signal S5 is being output from the unit 5, the signal supply unit 2 is controlled to reduce either the voltage value or the current value of the AC signal Vs. Therefore, according to this impedance measuring apparatus 1, even when the voltage value of the AC signal Vs becomes equal to or higher than a predetermined value when the measurement object 11 is a nonlinear element such as a diode, the measurement object 11 flows through the measurement object 11. While automatically reducing either the voltage value or the current value of the AC signal Vs until the distortion rate of the AC signal Ss included in each waveform of the AC current I1 and the voltage V1 between both ends thereof is equal to or less than a specified value. Since the fact that there is a possibility of erroneous measurement can be displayed on the display unit 7 and the measurement of the impedance Z can be continued, the impedance Z can be accurately measured while avoiding erroneous measurement.

Incidentally, if example embodiment, the signal supplying section 2 described above for example for outputting the AC signal Vs as a test signal, a configuration for supplying the AC signal Vs DC voltage Vd is superimposed as a test signal to the measured object 11 It can also be adopted. Further, in the impedance measuring apparatus 1 adopting this configuration, the calculation control unit 6 displays a display unit indicating that there is a possibility of erroneous measurement together with the calculated impedance Z while the distortion detection unit 5 outputs the detection signal S5. 7, the signal supply unit 2 is controlled to increase either the voltage value or the current value of the DC voltage Vd. When the forward voltage is equal to or higher than a predetermined value (for example, 0.7 volts or higher), the diode that is the measurement object 11 has a substantially linear voltage-current characteristic. Therefore, also in the impedance measuring apparatus 1 adopting this configuration, when the measuring object 11 is a non-linear element such as a diode, it is included in each waveform of the alternating current I1 flowing through the measuring object 11 and the voltage V1 between both ends thereof. The display unit 7 displays that there is a possibility of an erroneous measurement while automatically increasing either the voltage value or the current value of the DC voltage Vd until the distortion rate of the AC signal Ss is less than a specified value. Since the measurement of the impedance Z can be continued, the correct impedance Z can be measured while avoiding erroneous measurement.

  In addition, the example in which the distortion detection unit 5 and the calculation control unit 6 are configured separately has been described above. However, the calculation control unit 6 generates the AC current I1 and the voltage V1 based on the input digital data Di and digital data Dv. It is also possible to employ a configuration for detecting whether or not a distortion exceeding a specified value is generated in each waveform, that is, a configuration in which the arithmetic control unit 6 functions also as the distortion detection unit 5. In addition, while the detection signal S5 is input, the example in which the calculated impedance Z and the possibility of erroneous measurement are displayed on the display unit 7 constituted by the LCD has been described above. However, the detection signal S5 is input. It is also possible to adopt a configuration in which an LED, a lamp, or the like as a display unit is lit only while the display unit is on. Further, the example of measuring (calculating) the impedance Z of the diode as the measurement object 11 has been described above. However, if the electronic component exhibits nonlinear voltage-current characteristics, the impedance measuring device 1 can use the impedance measuring device 1 to connect the impedance Z other than the diode. Of course, it can be measured.

  Further, the signal supply unit 2 is configured to have both the function of reducing the voltage value of the AC signal Vs and the function of superimposing the DC voltage Vd on the AC signal Vs and increasing the voltage value of the DC voltage Vd. You can also. According to this configuration, the arithmetic control unit 6 automatically switches between the decrease in the voltage value of the AC signal Vs and the increase in the voltage value of the DC voltage Vd, whereby the two types of impedance Z (the DC voltage Vd described above). , The impedance in the operating region where the diode is on and the operating region where the diode is not on) can be automatically measured.

1 is a block diagram showing a configuration of an impedance measuring device 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Impedance measurement apparatus 2 Signal supply part 5 Strain detection part 6 Operation control part 11 Measurement object I1 Current ME measurement part Vs AC signal Z Impedance

Claims (3)

A signal supply unit that supplies an inspection signal to the measurement object, an alternating current that flows through the measurement object when the inspection signal is supplied, and is generated at both ends of the measurement object due to the supply of the alternating current A measurement unit that measures the impedance of the measurement object based on the voltage between both ends,
The signal supply unit supplies an AC signal on which a DC signal is superimposed as the inspection signal to the measurement object,
The measurement unit detects a distortion of the inspection signal included in at least one of the alternating current and the voltage between both ends, and outputs a detection signal when the distortion is a specified value or more, An impedance measuring apparatus comprising: a control unit that controls the signal supply unit to increase either the voltage value or the current value of the DC signal when the detection signal is output from a distortion detection unit. The strain detection unit, according to claim 1 Symbol placement of the impedance measuring device for detecting the distortion of the test signal by the Fourier transform operation. The strain detection unit is configured with a band elimination filter, the impedance of claim 1 Symbol placement detecting the distortion of the test signal based on the harmonic component of the test signal which passes through the band-elimination filter measuring device.

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