JP5774370B2 - Waveform measuring device - Google Patents

Description

  The present invention relates to a waveform measuring apparatus that measures waveforms such as voltage and current to be measured.

  An inverter power source for converting a DC power source into an AC power source is used for driving a motor of an automobile. An oscilloscope is used to measure whether or not the voltage or current converted into the AC power supply by the inverter power supply is normal. A differential probe is connected to the oscilloscope, and the output waveform of the inverter power supply is measured using this differential probe. Thereby, the voltage and current of the inverter power supply are measured. As this type of technology, there is a technology disclosed in Patent Document 1.

JP 2010-158152 A

  In general, a waveform measuring instrument such as an oscilloscope can measure a waveform of a voltage having a wide frequency band, but the accuracy (accuracy) of the measured waveform is lowered (uncertain) due to the wide band. When extremely high accuracy is required for the waveform of the voltage to be measured, an oscilloscope that supports a wide band cannot satisfy the requirement.

  On the other hand, a waveform measuring instrument that performs waveform measurement with higher accuracy than an oscilloscope can be used. Thereby, it is possible to cope with a case where high accuracy is required for waveform measurement. However, waveform measuring instruments that measure with high accuracy cannot measure broadband frequencies. That is, the frequency band to be measured is a narrow band.

  Therefore, waveform measuring instruments that measure voltage and current waveforms cannot prioritize measurement of wideband frequencies, but cannot prioritize measurement of wideband frequencies when prioritizing measurement with high accuracy. In some cases, the accuracy of measurement decreases.

  Therefore, an object of the present invention is to perform waveform measurement with a high accuracy and a wide frequency range.

  In order to solve the above problems, a waveform measuring apparatus of the present invention measures a first waveform measuring instrument that measures a waveform, and the waveform with a lower accuracy and a wider frequency than the first waveform measuring instrument. A second waveform measuring device; and a calculation unit for calculating an error of the second waveform data measured by the second waveform measuring device with reference to the first waveform data measured by the first waveform measuring device; And a correction unit that corrects the second waveform data by the amount of the error.

  According to this waveform measuring apparatus, an error occurring in the second waveform data is corrected based on the first waveform data with high accuracy. This makes it possible to correct the broadband second waveform data with high accuracy, and to perform high-accuracy and broadband waveform measurement.

  Further, the calculation unit calculates the error based on the gain and offset of the second waveform data with respect to the gain and offset of the first waveform data.

  By comparing the gain and offset between the first waveform data and the second waveform data, it is possible to calculate the error of the second waveform data when the first waveform data with high accuracy is used as a reference, Highly accurate and broadband waveform measurement can be performed.

  The second waveform data includes a frequency filter that extracts only a component of a frequency band measured by the first waveform measuring instrument, and the arithmetic unit is configured to extract the second waveform extracted by the frequency filter. The error is calculated based on data and the first waveform data.

  The frequency band of the second waveform data overlaps with the frequency band of the first waveform data, but the second waveform data has a wide band. Therefore, by extracting a band that overlaps the first waveform data from the second waveform data, it is possible to unify the reference of the waveform to be compared when calculating the error, and to perform a simple calculation. .

Moreover, the preset portion is larger waveform than the change amount is changed among the second waveform data corrected by the correction unit using the second waveform data corrected by the correction unit, The other part includes a waveform synthesis unit that synthesizes using the first waveform data.

  Since the second waveform data has a lower accuracy than the first waveform data, a high-speed waveform change can be measured. The second waveform data is used for the portion where the waveform changes at high speed, and the first waveform data with high accuracy is used for the other portion where the waveform changes at low speed, so that the waveform is measured accurately and at high speed. be able to.

  In addition, a trigger signal indicating the start of the measurement of the waveform is output from any one of the first waveform measuring device and the second waveform measuring device to the other.

  The first waveform measuring instrument and the second waveform measuring instrument must measure the same waveform to be measured. Therefore, by outputting the trigger signal, the first waveform measuring device and the second waveform measuring device can be synchronized, and accurate waveform measurement can be performed.

  Since the present invention corrects the error of the waveform data of the second waveform measuring device that measures the waveform of the broadband frequency with reference to the waveform data of the first waveform measuring device with high accuracy, the high accuracy and wide bandwidth. It becomes possible to measure the waveform of the frequency.

It is a block diagram which shows the structure of the waveform measuring apparatus of embodiment. It is a block diagram which shows the structure of a waveform process part. It is the figure which showed an example of the waveform processed by each part.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a waveform measuring apparatus 1 according to the embodiment. 1 includes a measurement object 2, a floating voltage unit 3, a differential probe 4, a high-precision waveform measurement device 5, a wide-band waveform measurement device 6, a waveform processing unit 7, and a waveform display unit 8. ing.

  The measurement object 2 is an object for waveform measurement. The measurement target includes an inverter power source that performs conversion from a DC power source to an AC power source. Of course, any object can be applied as the measurement object 2 as long as it outputs a waveform such as current or voltage. The floating voltage unit 3 floats a predetermined voltage from the ground having a potential of 0 volts.

  The differential probe 4 is connected to the positive side and the negative side (voltage of the floating voltage unit 3) of the measurement object 2 to detect the differential voltage. The differential voltage detected by the differential probe 4 is output to the broadband waveform measuring device 6. Therefore, the wideband waveform measuring instrument 6 measures the differential voltage detected by the differential probe 4, that is, the waveform of the voltage of the measuring object 2.

  The high-precision waveform measuring instrument 5 is a first waveform measuring instrument, and inputs the positive side and the negative side of the measuring object 2. Thereby, the waveform of the voltage of the measuring object 2 is measured. The broadband waveform measuring device 6 is a second waveform measuring device, and measures the waveform of the voltage of the measuring object 2 detected by the differential probe 4. Therefore, the high-precision waveform measuring instrument 5 and the broadband waveform measuring instrument 6 measure the same waveform.

  The high-precision waveform measuring instrument 5 can perform waveform measurement with higher accuracy (accuracy) than the broadband waveform measuring instrument 6. Thereby, the waveform measured by the high-precision waveform measuring instrument 5 is more accurate than the waveform measured by the broadband waveform measuring instrument 6. However, since the accuracy is high, only a narrow frequency band is measured. In particular, only the low frequency band is measured. For example, a waveform in a narrow low frequency band from DC to 10 MHz is a measurement target.

  The broadband waveform measuring device 6 can measure a broadband waveform. For example, a waveform in a wide frequency band from direct current to several hundred MHz or more is a measurement target. The frequency band to be measured by the wide-band waveform measuring instrument 6 includes the frequency band to be measured by the high-precision waveform measuring instrument 5. However, since a wide frequency band can be measured, the accuracy of waveform measurement of the wide-band waveform measuring device 6 is lower than that of the high-precision waveform measuring device 5.

  A trigger signal trig is output from the high precision waveform measuring instrument 5 to the wideband waveform measuring instrument 6. Thereby, the measurement start timing of the high-precision waveform measuring instrument 5 and the measurement start timing of the broadband waveform measuring instrument 6 are synchronized. By taking this synchronization, the high-precision waveform measuring instrument 5 and the broadband waveform measuring instrument 6 can start waveform measurement at the same timing, and the same waveform can be measured. Note that the trigger signal may be output from the broadband waveform measuring device 6 to the high-precision waveform measuring device 5.

  The waveform measured by the high precision waveform measuring instrument 5 is output to the waveform processing unit 7 as high precision waveform data (first waveform data) HD. The waveform measured by the broadband waveform measuring device 6 is output to the waveform processing unit 7 as broadband waveform data (second waveform data) WD. The waveform processing unit 7 performs processing based on the high-precision waveform data HD and the broadband waveform data WD.

  As shown in FIG. 2, the waveform processing unit 7 includes a high-precision waveform data input unit 11, a broadband waveform data input unit 12, a low-pass filter 13, a calculation unit 14, a correction unit 15, and a waveform synthesis unit 16. Yes. The high-precision waveform data input unit 11 outputs the input high-precision waveform data HD to the calculation unit 14 and the waveform synthesis unit 16. The broadband waveform data input unit 12 outputs the input broadband waveform data WD to the low-pass filter 13 and the correction unit 15.

  The low-pass filter 13 is a frequency filter that extracts only low-frequency components from the broadband waveform data WD. The frequency component extracted by the low-pass filter 13 is matched with the frequency band to be measured by the high-precision waveform measuring instrument 5.

  Broadband waveform data WD obtained by extracting only the same frequency component as that of the high-precision waveform data HD by the low-pass filter 13 is input to the calculation unit 14. The calculation unit 14 receives the high-precision waveform data HD and the broadband waveform data WD after passing through the filter (low-pass filter 13). Then, the error amount (gain error ΔG and offset error ΔA) is calculated using the high-accuracy waveform data HD and the broadband waveform data WD after passing through the filter.

  The correction unit 15 receives the broadband waveform data WD from the broadband waveform data input unit 12. Then, the broadband waveform data WD is corrected based on the error amount calculated by the calculation unit 14. The corrected broadband waveform data WD is output to the waveform synthesizer 16.

  A change amount threshold is set in the waveform synthesizer 16. If the change amount of the corrected wideband waveform data WD exceeds the threshold, the wideband waveform data WD is used, and otherwise (below the threshold). Synthesizes the waveform so as to use the high-precision waveform data HD. The synthesized waveform data is output to the waveform display unit 8 as synthesized waveform data CD. The waveform display unit 8 is a display device such as a display, and displays the composite waveform data CD. Thereby, the waveform of the output voltage of the measuring object 2 can be recognized by visually recognizing the waveform display unit 8.

  Next, the operation will be described. The measurement object 2 outputs an alternating voltage. The voltage of the measuring object 2 is input to the high-precision waveform measuring instrument 5 and the differential probe 4. The differential voltage input to the differential probe 4 is input to the broadband waveform measuring device 6. For this reason, the high-precision waveform measuring instrument 5 and the broadband waveform measuring instrument 6 measure the waveform of the same voltage of the measuring object 2. The object to be measured may be a current using a current probe or the like instead of the differential probe.

  The high precision waveform measuring instrument 5 outputs a trigger signal trig to the wideband waveform measuring instrument 6. As a result, the high-precision waveform measuring instrument 5 and the broadband waveform measuring instrument 6 start measuring waveforms at the same timing. The waveform measured by the high-precision waveform measuring device 5 is input to the waveform processing unit 7 as high-precision waveform data HD, and the waveform measured by the wide-band waveform measuring device 6 is input as wide-band waveform data WD.

  The high-precision waveform data input unit 11 of the waveform processing unit 7 inputs high-precision waveform data HD, and the wide-band waveform data input unit 12 inputs wide-band waveform data WD. An example of the high-precision waveform data HD and the broadband waveform data WD at this time is shown in FIG. Note that the high-precision waveform data HD and the wide-band waveform data WD in FIG.

  From the broadband waveform data WD input by the broadband waveform data input unit 12, only a low frequency component is extracted by the low pass filter 13. At this time, the frequency band of the low-pass filter 13 is matched with the frequency band of the high-precision waveform measuring instrument 5. For example, if the high-accuracy waveform measuring instrument 5 measures from DC to 10 MHz, the low-pass filter 13 extracts only the frequency band from DC to 10 MHz out of DC to 500 MHz.

  As a result, the frequency band of the wideband waveform data WD after passing through the filter matches the frequency band of the high-precision waveform data HD. The calculation unit 14 performs a calculation by comparing the broadband waveform data WD having the same frequency band with the high-precision waveform data HD. The solid line in FIG. 3b) is the high-precision waveform data HD, and the broken line is the broadband waveform data WD after passing through the filter.

  Since the wideband waveform measuring instrument 6 has a wide frequency band as a measurement target, the accuracy decreases. That is, a predetermined error occurs. On the other hand, the high-precision waveform measuring instrument 5 uses a narrow-band frequency as a measurement target, and performs measurement with high accuracy. Therefore, the amount of error occurring in the broadband waveform data WD is calculated using the high-precision waveform data HD as a reference.

  Here, the error amounts are calculated as a gain error ΔG and an offset error ΔA. However, the calculation may be performed using parameters other than the gain error ΔG and the offset error ΔA as long as the error amount of the wideband waveform data WD when the high-precision waveform data HD is used as a reference can be calculated.

  The gain error ΔG is obtained by calculating the ratio between the amplitude GH of the high-precision waveform data HD and the amplitude GW of the wideband waveform data WD. That is, the gain error ΔG is “ΔG = GW / GH”. This gain error ΔG indicates a gain error of the wide-band waveform measuring instrument 6 with respect to the high-precision waveform measuring instrument 5.

  The offset error ΔA is obtained by calculating the difference between the offset AH of the high-precision waveform data HD and the offset AW of the wideband waveform data WD. That is, the offset error ΔA is “ΔA = AW−AH”. The offset error ΔA indicates an offset error of the wide-band waveform data WD with respect to the high-precision waveform data HD. Note that “offset” refers to a DC offset component with respect to a predetermined reference voltage.

  The above gain error ΔG and offset error ΔA are errors of the wide band waveform data WD when the high precision waveform data HD is used as a reference. The calculation unit 14 calculates this error. The calculated gain error ΔG and offset error ΔA are output to the correction unit 15. The correction unit 15 receives the broadband waveform data WD (data not passing through the low-pass filter 13) from the broadband waveform data input unit 12, and corrects the broadband waveform data WD.

  The correction unit 15 corrects the gain by the gain error ΔG with respect to the wideband waveform data WD and corrects the offset by the offset error ΔA. As a result, the error when the highly accurate waveform data HD with high accuracy is used as a reference can be corrected for the wideband waveform data WD. The corrected broadband waveform data WD is output to the waveform synthesizer 16.

  The waveform synthesizer 16 receives the high-accuracy waveform data HD from the high-accuracy waveform data input unit 11 and the corrected wide-band waveform data WD from the correction unit 15. Then, the high-accuracy waveform data HD and the broadband waveform data WD are synthesized and output to the waveform display unit 8 as synthesized waveform data CD.

  As described above, the waveform composition unit 16 is preset with a change amount threshold. This threshold value can be set appropriately. The waveform synthesizer 16 can detect the amount of change in the waveform of the broadband waveform data WD by differentiating the broadband waveform data WD based on the time and the voltage value. It is detected whether or not the amount of change detected at this time exceeds a threshold value.

  That is, it is detected whether or not a rapid change that exceeds the set threshold value has occurred in the broadband waveform data WD. Broadband waveform data WD is adopted assuming that a rapid change occurs when the amount of change obtained by differentiation exceeds a threshold value. On the other hand, when it is other than that (the amount of change is equal to or less than the threshold value), the high-precision waveform data HD is adopted assuming that there is no sudden change.

  As a result, the portion having a large change can be processed at high speed by using the broadband waveform data WD, and the broadband waveform data WD is corrected with high accuracy. Can be high. On the other hand, with respect to a portion where a large change has not occurred, highly accurate waveform data HD can be measured by using highly accurate waveform data HD, and high-speed and accurate waveform measurement can be performed.

  As described above, using two waveform measuring devices (high-precision waveform measuring device 5 and wide-band waveform measuring device 6) having different accuracy and frequency band, a wide-band wideband based on high-precision waveform data HD with high accuracy. The waveform data WD is corrected. This makes it possible to measure a highly accurate and wide-band waveform.

  In the above, the wideband waveform data WD and the high-precision waveform data HD are synthesized by the waveform synthesis unit 16, but the processing of the waveform synthesis unit 16 may be omitted. That is, the correction unit 15 performs correction on the wideband waveform data WD based on the highly accurate high-precision waveform data HD, and the accuracy of the wideband waveform data WD is increased. For this reason, the waveform synthesis by the waveform synthesis unit 16 need not be performed. Therefore, in this case, the corrected broadband waveform data WD is displayed on the waveform display unit 8.

  Further, although the waveform processing unit 7 is an independent device, it may be provided in either the high-precision waveform measuring instrument 5 or the broadband waveform measuring instrument 6. In particular, when a digital oscilloscope is applied to the broadband waveform measuring instrument 6, the digital oscilloscope having a complicated circuit can easily have the function of the waveform processing unit 7. Of course, the waveform processing unit 7 may be configured as an independent device such as a computer to perform waveform processing.

  Further, although the floating voltage unit 3 forms a floating voltage, the floating voltage unit 3 is not an essential component. Further, when a difference in processing speed occurs between the high-precision waveform measuring instrument 5 and the wide-band waveform measuring instrument 6, the earlier measuring instrument is made to follow the measuring instrument having the slower processing speed. Also good.

DESCRIPTION OF SYMBOLS 1 Waveform measuring apparatus 2 Measuring object 5 High precision waveform measuring instrument 6 Wideband waveform measuring instrument 7 Waveform processing part 8 Waveform display part 11 High precision waveform data input part 12 Wideband waveform data input part 13 Low pass filter 14 Calculation part 15 Correction part 16 Waveform Compositing part

Claims (5)

A first waveform measuring instrument for measuring a waveform;
A second waveform measuring instrument that measures the waveform with a lower accuracy and a wider frequency range than the first waveform measuring instrument;
A computing unit for computing an error of the second waveform data measured by the second waveform measuring device with reference to the first waveform data measured by the first waveform measuring device;
A correction unit that corrects the second waveform data by the amount of the error;
A waveform measuring apparatus comprising: The waveform measurement apparatus according to claim 1, wherein the calculation unit calculates the error based on a gain and an offset of the second waveform data with respect to a gain and an offset of the first waveform data. A frequency filter that extracts only the component of the frequency band measured by the first waveform measuring instrument from the second waveform data;
The waveform measuring apparatus according to claim 2, wherein the calculation unit calculates the error based on the second waveform data and the first waveform data extracted by the frequency filter. The preset portion is larger waveform than the change amount is changed among the second waveform data corrected by the correction unit using the second waveform data corrected by the correction unit, otherwise The waveform measuring apparatus according to claim 3, further comprising: a waveform synthesis unit configured to synthesize using the first waveform data. The waveform according to claim 4, wherein a trigger signal indicating the start of measurement of the waveform is output from one of the first waveform measuring device and the second waveform measuring device to the other. measuring device.

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