JP5693289B2 - Measuring apparatus and measuring method - Google Patents

Description

  The present invention relates to a measuring apparatus and a measuring method for measuring a measured value such as an effective value of a signal to be measured.

  As this type of measuring apparatus, the applicant has already proposed a measuring apparatus (effective value measuring apparatus) disclosed in Patent Document 1 below. This measurement apparatus includes an A / D conversion unit, an effective value calculation unit, an operation unit, a control unit, and a display unit, and is configured to be able to measure a measurement value (an effective value as an example) of an input measurement target signal. In this case, the effective value calculation unit includes a data extraction unit, a windowing processing unit, a square processing unit, a filter processing unit, an average processing unit, a square root processing unit, and a correction unit, and a measurement target output from the A / D conversion unit Based on the sampling data for the signal, the effective value of the signal to be measured is calculated and output.

  In this measuring apparatus, a windowing process is performed on a predetermined number of sampling data for a signal to be measured to obtain window data, and effective values such as a square process, a filtering process, an average process, and a square root process are performed on the window data. After performing the basic processing for calculation, the square root data obtained by these processings is subjected to processing for correcting the attenuation during the windowing processing, and the effective value of the measurement target signal is calculated. Therefore, according to this measuring apparatus, even if the period of the measurement target signal and the sampling period are asynchronous due to the unknown period of the measurement target signal, the measurement target included in the predetermined number of sampling data It is possible to significantly reduce an error caused by the fluctuation of the signal phase by the windowing process.

  Further, when the number of waveforms of the measurement target signal included in the predetermined number of sampling data subjected to the windowing process is small, the measurement accuracy of the effective value is lowered. For this reason, in this measurement apparatus, when the number of waveforms of the measurement target signal included in the predetermined number of sampling data is small, the sampling period of the A / D conversion unit is lengthened to increase the number of waveforms of the measurement target signal included. The structure which can be used is adopted.

JP 2010-60378 (page 3-6, Fig. 1-2)

  However, in a low-priced measuring device, in order to reduce the product cost, the sampling period of the A / D conversion unit is made constant, and a predetermined number of sampling data is output from the sampling data output from the A / D conversion unit. Many of them employ a simple configuration in which the period to be cut out is constant (in other words, a simple configuration in which sampling data is divided into fixed intervals). Therefore, in such a measuring apparatus, there is a problem to be solved that the measurement accuracy with respect to a measurement target signal having a low frequency at which the number of waveforms included in the predetermined number of sampling data decreases is reduced.

  The present invention has been made to solve such a problem, and mainly provides a measuring apparatus and a measuring method capable of measuring a measurement value of a measurement target signal with high accuracy while suppressing an increase in apparatus cost. Objective.

In order to achieve the above object, the measuring apparatus according to claim 1 divides sampling data obtained by sampling a signal to be measured at a fixed sampling period into fixed intervals, and sets divided data composed of a fixed number of the sampling data. A windowing process in which the windowing process is executed by executing the windowing process on the classification data and any data before the windowing process of the calculated data calculated based on the classification data. a measuring apparatus equipped with a signal processing unit for calculating a measured value for the measurement target signal based on the post-data, met waveform number of the fundamental wave of the measurement object signal included in the prior SL predetermined section The number of waveforms at the boundary where the error caused by executing the windowing process is equal to or less than the error generated when the windowing process is not executed is Are previously defined as the number, the signal processing unit, when the waveform number of the fundamental wave is equal to or greater than the reference number, the calculated measurement value based on the windowing processing after the data, the number of waveforms of the fundamental wave Is less than the reference number, the measured value is calculated based on the pre-windowing data.

  The measuring device according to claim 2 is the measuring device according to claim 1, wherein the detecting unit detects any one of a frequency and a period of the measurement target signal as a detection target, the detected detection target, and the constant A discriminating unit that discriminates whether or not the number of waveforms of the fundamental wave included in the certain zone is greater than or equal to the reference number based on the zone length of the zone, and the signal processing unit includes the discrimination In accordance with the determination result of the part, the measurement value is calculated based on the data after the windowing process or the measurement value is calculated based on the data before the windowing process.

  Further, in the measurement apparatus according to claim 3, in the measurement apparatus according to claim 1 or 2, the signal processing unit executes a square process of squaring the segmented data to generate the calculation data, and the predetermined interval When the number of waveforms of the fundamental wave included in the reference number is greater than or equal to the reference number, a windowing process is performed on the calculated data to generate the windowed data, and the windowed data is The effective value of the signal to be measured is calculated as the measured value by executing a correction process that corrects the attenuation during the averaging process, the opening process, and the windowing process, and is included in the predetermined section. When the number of waveforms of the fundamental wave is less than the reference number, the calculated data is used as the pre-windowing data without performing the windowing process on the calculated data. Calculating the effective value by performing the averaging process and the open way process on data.

  The measuring apparatus according to claim 4 is the measuring apparatus according to claim 1 or 2, wherein the signal processing unit is configured such that when the number of waveforms of the fundamental wave included in the certain section is equal to or greater than the reference number. A windowing process is performed on the segmented data to generate the windowed data, and a squared process, an average process, an opening process, and an attenuation during the windowing process are performed on the windowed data. The effective value of the signal to be measured is calculated as the measured value by executing a correction process for correcting the measured signal. When the number of waveforms of the fundamental wave included in the certain interval is less than the reference number, the segment data The square data, the averaging process, and the opening process are performed on the pre-windowing data without performing the windowing process on the data. Calculating the effective value by.

  The measurement apparatus according to claim 5 is the measurement apparatus according to claim 1 or 2, wherein the signal processing unit executes absolute value calculation processing for calculating an absolute value of the segment data and generates the calculated data. When the number of waveforms of the fundamental wave included in the certain interval is equal to or greater than the reference number, the calculated data is subjected to windowing processing to generate the windowed data and the windowing The average value of the signal to be measured is calculated as the measurement value by executing an average process on the post-processing data and a correction process for correcting the attenuation during the windowing process, and is included in the predetermined section. When the number of waveforms of the fundamental wave is less than the reference number, the calculated data is used as the pre-windowing data without performing the windowing process on the calculated data. Calculating the AC mean value by performing the averaging process on pre-processing data.

  The measuring device according to claim 6 is the measuring device according to claim 1 or 2, wherein the signal processing unit is configured such that when the number of waveforms of the fundamental wave included in the certain section is equal to or greater than the reference number. A windowing process is performed on the segmented data to generate post-windowing data, an average process is performed on the post-windowing data, and a correction process is performed to correct an attenuation during the windowing process. A DC average value of the measurement target signal is calculated as the measurement value by executing, and when the number of waveforms of the fundamental wave included in the certain interval is less than the reference number, a windowing process is performed on the segmented data. The DC average value is calculated by executing the averaging process on the pre-windowing data as the pre-windowing data without executing the classification data.

In order to achieve the above object, the measuring method according to claim 7 divides sampling data obtained by sampling a signal to be measured at a fixed sampling period into fixed intervals, and sets divided data composed of a fixed number of the sampling data. A windowing process in which the windowing process is executed by executing the windowing process on the classification data and any data before the windowing process of the calculated data calculated based on the classification data. A measurement method for calculating a measurement value for the measurement target signal based on post-data, which is the number of waveforms of the fundamental wave for the measurement target signal included in the certain section and executes the windowing process The number of waveforms at the boundary where the error caused by performing the windowing process is less than or equal to the error generated when the windowing process is not executed is defined in advance as a reference number. Are, when the waveform number of the fundamental wave is equal to or greater than the reference number, the calculating the measured values based on the windowed processed data, when the number of waveforms of the fundamental wave is less than the reference number of the window The measured value is calculated based on the pre-multiplication data.

  In the measuring apparatus according to claim 1 and the measuring method according to claim 7, whether the fundamental wave of the signal to be measured exceeds a reference number in a certain section applied when sampling data is divided when calculating a measurement value If it is not included based on whether or not the windowing process is not executed without executing the windowing process on either the classification data or the calculation data calculated based on the classification data, A measurement value for the measurement target signal is calculated based on the pre-processing data.

  Therefore, according to the measurement apparatus and the measurement method, the windowing process is executed in a state where the fundamental wave of the measurement target signal included in the certain section does not reach the reference number (state less than the reference number). Therefore, even in such a state, the measurement value of the measurement target signal can be measured with high accuracy.

  According to the measuring apparatus of claim 2, the detection unit and the determination unit are provided separately from the signal processing unit, the detection unit detects either the frequency or the period of the measurement target signal as the detection target, and the determination unit Based on the detection target and the section length of the fixed section, it is determined whether or not the fundamental wave of the measurement target signal is included in the fixed section or more than the reference number, and the determination result is output to the signal processing unit As a result, the processing of the signal processing unit can be reduced. As a result, when the signal processing unit is configured by a DSP, an inexpensive DSP can be used, thereby reducing the apparatus cost.

  According to the measuring apparatus according to claim 3 and the measuring apparatus according to claim 4, the windowing process is performed in a state where the fundamental wave of the measurement target signal included in the certain section does not reach the reference number (state less than the reference number). It is possible to accurately measure an effective value as a measured value while avoiding an increase in errors caused by executing the above.

  According to the measurement apparatus of claim 5, the windowing process is executed in a state where the fundamental wave of the measurement target signal included in the certain section does not reach the reference number (state less than the reference number). It is possible to accurately measure the AC average value as a measurement value while avoiding an increase in generated error.

  According to the measurement apparatus of claim 6, the windowing process is executed in a state where the fundamental wave of the measurement target signal included in the certain section does not reach the reference number (state less than the reference number). It is possible to accurately measure the DC average value as a measurement value while avoiding an increase in the generated error.

1 is a configuration diagram of a measuring device 1. FIG. Error in effective value when windowing process is performed (when windowing process is performed) when frequency of measurement target signal Si is changed, and effective when windowing process is not performed (when windowing process is not performed) It is an experimental result figure which shows the difference | error of a value. 5 is a flowchart for explaining an operation of an effective value calculation process 50; 6 is a flowchart for explaining an operation of an AC average value calculation process 60; 6 is a flowchart for explaining the operation of a DC average value calculation process 70; It is a flowchart for demonstrating operation | movement of the other effective value calculation process 50A.

  Hereinafter, embodiments of a measurement apparatus and a measurement method will be described with reference to the accompanying drawings.

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

  As shown in FIG. 1, the measuring device 1 includes a direct current removing unit 2, a signal switching unit 3, a detection unit 4, a determination unit 5, an A / D conversion unit 6, a signal processing unit 7, an operation unit 8, a control unit 9, and The display unit 10 is provided so that the measurement value Dm (effective value Dm1, AC average value Dm2, and DC average value Dm3) of the input measurement target signal Si (analog signal) can be measured.

  The direct current removing unit 2 is configured by a capacitor as an example, and inputs the measurement target signal Si and removes a direct current component contained in the measurement target signal Si, and outputs a first measurement signal S1 as an alternating current signal. To do. The signal switching unit 3 is configured by a changeover switch, receives the measurement target signal Si and the first measurement signal S1, and controls the switching state based on the control signal Sc1 output from the control unit 9. One of these signals Si and S1 is output as the second measurement signal S2.

  The detection unit 4 includes, as an example, a comparator, a counter, and an arithmetic circuit (all not shown), and either one of the frequency and cycle of the input first measurement signal S1 (in this example, the frequency f1 as an example). ) As a detection target. Specifically, in the detection unit 4, the comparator detects a zero cross point of the first measurement signal S1, thereby generating a synchronization signal synchronized with one cycle (or half cycle) of the first measurement signal S1. Next, the counter performs a counting operation at a constant cycle (a known cycle sufficiently early with respect to the cycle of the measurement target signal Si), and measures the count value within one cycle of the synchronization signal output from the comparator. And output. Finally, the arithmetic circuit calculates and outputs the frequency data Df based on the count value. In this case, as described above, since the count cycle of the counter is known and the synchronization signal is one cycle (or half cycle) of the first measurement signal S1, the arithmetic circuit can calculate the count cycle and the count value. When the synchronization signal is one cycle of the first measurement signal S1, the multiplication value is calculated. When the synchronization signal is the half cycle of the first measurement signal S1, the multiplication value is calculated. Based on a value twice that of the first measurement signal S1, the frequency f1 of the first measurement signal S1 is calculated and output as frequency data Df. It is also possible to employ a configuration in which the reciprocal of the frequency f1 is calculated to calculate the period of the first measurement signal S1 as a detection target and to output data indicating this period (period data).

  The determination unit 5 receives the frequency data Df output from the detection unit 4, and the frequency f1 of the first measurement signal S1 indicated by the frequency data Df, and the signal processing unit 7 receives the waveform data Dw as described later. Based on the section length of the certain section divided into the section data, the number of waveforms of the fundamental wave for the measurement target signal Si included in the certain section is detected, and the detected number of waveforms and a predetermined reference number And compare. Further, the determination unit 5 generates a control signal Sc2 whose level changes based on the comparison result, and outputs the control signal Sc2 to the signal processing unit 7. In this example, as an example, the discriminating unit 5 is set to the Low level when the number of waveforms of the fundamental wave included in the predetermined section is equal to or higher than the reference number, and is set to the High level when the number of waveforms of the fundamental wave is less than the reference number. A control signal Sc2 is generated and output as a discrimination result.

  As will be described later, the signal processing unit 7 divides the waveform data Dw into fixed intervals, generates divided data composed of a fixed number of waveform data Dw, and normally performs a windowing process on the divided data. The measured value Dm is calculated based on the data obtained by the windowing process. In this case, when the number of waveforms of the fundamental wave of the measurement target signal Si included in a certain section when the waveform data Dw is divided into divided data is greater than a predetermined reference number, measurement is performed by executing windowing processing. While the value Dm can be calculated with higher accuracy than when the value Dm is calculated without executing the windowing process, the number of waveforms of the fundamental wave of the measurement target signal Si included in the predetermined section is the above. When the number is less than the reference number, an error caused by executing the windowing process becomes large. Therefore, the measurement value Dm is calculated without performing the windowing process than when the windowing process is performed. It was confirmed by the inventors' experiments and simulations that the measured value Dm can be calculated with high accuracy.

  The result of this simulation is shown in FIG. In this simulation, the measurement target signal Si is a sine wave. First, while changing the frequency of the measurement target signal Si, the phases of the measurement target signal Si and the constant section to be described later are shifted little by little at each frequency. By dividing the waveform data Dw of the measurement target signal Si into a certain section (100 ms), a plurality of pieces of section data (section data whose phases are shifted) are created for each frequency. Next, a measurement value calculation process including a windowing process (here, an effective value calculation process) and a measurement value calculation process not including a windowing process are respectively performed on these segmented data, and the measurement target signal Si The measured value (effective value) was calculated, and the maximum and minimum difference between the measured values for each frequency was calculated as an error. In this windowing process, a Blackman-Harris window function is used as an example.

  According to the simulation result, when the number of waveforms of the fundamental wave with respect to the measurement target signal Si included in the certain section is less than 1 (in other words, the frequency of the measurement target signal Si is less than 10 Hz (the cycle exceeds 100 ms). In this case, the error caused by executing the windowing process greatly exceeds the error caused when the windowing process is not executed. However, when the number of waveforms of the fundamental wave included in a certain interval is 1, the error that occurs when the windowing process is performed is equal to the error that occurs when the windowing process is not performed, and the fundamental included in the certain interval When the number of wave waveforms exceeds 1, it has been confirmed that an error caused by executing the windowing process is smaller than an error occurring when the windowing process is not executed. Therefore, the number of waveforms at the boundary where the error caused by executing the windowing process is equal to or less than the error generated when the windowing process is not executed (numerical value “1” in this example) is defined as the reference number. .

  Although the simulation result is not particularly shown, even when the measurement target signal Si is not a sine wave but a signal composed of a repetitive waveform of another shape such as a triangular wave or a rectangular wave, the same as in the case of the sine wave. It has been confirmed that there is a boundary where the error caused by executing the windowing process is equal to or less than the error generated when the windowing process is not performed, and the number of waveforms at this boundary is defined as the reference number. The

  The A / D converter 6 includes an A / D converter that performs sampling at a predetermined constant sampling period (a fixed sampling period sufficiently earlier than the period of the measurement target signal Si). With this configuration, the A / D conversion unit 6 inputs the second measurement signal S2 output from the signal switching unit 3 and samples it, thereby sampling data (data indicating an instantaneous value of the amplitude of the second measurement signal S2). ) And the converted sampling data is output as waveform data Dw.

  The signal processing unit 7 is configured by a DSP (Digital Signal Processor) as an example, and based on the waveform data Dw output from the A / D conversion unit 6, the measurement value Dm (effective value Dm1, AC average value Dm2 and DC average value Dm3) are calculated and output. In this case, the signal processing unit 7 is based on the control signal Sc3 output from the control unit 9 to calculate the effective value Dm1, the effective value calculation process, the AC average value calculation process to calculate the AC average value Dm2, and the DC average. One of the DC average value calculation processes for calculating the value Dm3 is selected and executed as the measurement value calculation process.

  In addition, the signal processing unit 7 calculates the measurement value in a mode including the windowing process and the windowing process based on the level of the control signal Sc2 output from the determination unit 5 in the execution state of each measurement value calculation process. One of the measurement value calculations in a mode that does not include is selected and executed. In this example, as described above, the second measurement signal S2 is at the low level when the number of waveforms of the measurement target signal Si included in the certain section is equal to or higher than the reference number, and this fundamental wave included in the certain section. When the number of waveforms is less than the reference number, the level is high. For this reason, the signal processing unit 7 measures the measured value in a mode including a windowing process when the reference wave number of the measurement target signal Si is greater than the reference number in a certain section (when the control signal Sc2 is at the low level). The calculation is executed, and when the fundamental wave for the measurement target signal Si is not included in a certain section in a predetermined number or more (when the control signal Sc2 is at the high level), the measurement value calculation in a mode not including the windowing process is performed. Run.

  The operating unit 8 selects a measurement value Dm (measurement value Dm1, AC average value Dm2, or DC average value Dm3) (not shown) for selecting a measurement value Dm for the measurement target signal Si measured by the measurement apparatus 1 (for example, , A rotary switch), and outputs selection data Ds corresponding to the operation content of the selection switch to the control unit 9. The control unit 9 includes a CPU and a memory (both not shown), and outputs control signals Sc1 and Sc3 based on the input selection data Ds, thereby switching control for the signal switching unit 3. Execution process selection control for the signal processing unit 7 is executed. The control unit 9 also executes display processing for causing the display unit 10 to display the measurement value Dm calculated by the signal processing unit 7. The display unit 10 is configured by a monitor device such as a liquid crystal display, for example, and displays the measured value Dm output from the control unit 9 on the screen as a numerical value. Note that the display unit 10 may be configured by a printing device such as a printer instead of the monitor device.

  Next, the measurement method and the measurement operation of the measurement value Dm for the measurement target signal Si by the measurement apparatus 1 will be described.

  In the measuring apparatus 1, the direct current removing unit 2 removes the direct current component from the input measurement target signal Si and outputs it as the first measurement signal S1, and the detection unit 4 detects the frequency of the first measurement signal S1. The frequency data Df is output, and the determination unit 5 compares the frequency f1 of the first measurement signal S1 indicated by the frequency data Df with the section length of the predetermined section, and outputs the control signal Sc2. The A / D conversion unit 6 outputs the waveform data Dw by sampling the second measurement signal S2 output from the signal switching unit 3.

  First, the case where the operation unit 8 is operated in this state and the effective value Dm1 is selected as the measured value Dm to be calculated will be described.

  At this time, the operation unit 8 outputs selection data Ds indicating the selection content (content indicating that the effective value Dm1 is selected as the measured value Dm to be calculated) to the control unit 9. When the selection data Ds is input, the control unit 9 outputs the control signal Sc1 to control the switching state of the signal switching unit 3, thereby causing the signal switching unit 3 to measure the measurement target signal as the second measurement signal S2. An effective value calculation process for calculating an effective value Dm1 for the signal processing unit 7 by outputting Si to the A / D conversion unit 6 and outputting a control signal Sc3 to execute selection control on the signal processing unit 7. 50 (see FIG. 3) is started.

  In the effective value calculation process 50, the signal processing unit 7 first executes a data cut-out process to divide the waveform data Dw into fixed intervals and sequentially cut out a fixed number (predetermined number) of waveform data Dw. Thus, the division data is generated (step 51). Next, the signal processing unit 7 performs square processing on each waveform data Dw included in the segment data to generate square data (step 52). Subsequently, the signal processing unit 7 detects the level of the control signal Sc2 output from the determination unit 5 to determine whether or not the level is the low level (step 53). When the level is the low level, the square data ( A windowing process is executed by applying a window function to (calculated data calculated based on the classification data), and the processed data is generated as output data (data after the windowing process) (step 54). As a result of determination in step 53, when the level of the control signal Sc2 is high, square data is generated as output data (data before windowing process) without executing the windowing process.

  Next, the signal processing unit 7 calculates the moving average of the output data by executing an averaging process on the output data, generates the average data (step 55), and subsequently performs an opening process on the average data. By executing this, the square root of the average data is calculated to generate square root data (step 56). Next, the signal processing unit 7 determines whether or not the windowing process in step 54 has been executed (step 57). When the windowing process is being executed, the attenuation amount during the windowing process is applied to the square root data. Is executed to generate an effective value Dm1 of the measurement target signal Si (step 58). On the other hand, when the windowing process is not executed, the square root data is generated as the effective value Dm1 of the measurement target signal Si without executing the correction process. Thereby, the effective value calculation process 50 is completed. The signal processing unit 7 outputs the generated effective value Dm1 to the control unit 9 after the effective value calculation processing 50 is completed.

  The control unit 9 causes the display unit 10 to display the effective value Dm1 input from the signal processing unit 7. Thereby, the measurement of the effective value Dm1 by the measuring apparatus 1 is completed. In the measurement apparatus 1, in a state where the effective value Dm 1 is selected as the measurement value Dm to be calculated, the signal processing unit 7 repeatedly executes the effective value calculation process 50 and outputs the effective value Dm 1 to the control unit 9. Therefore, the control unit 9 displays the new effective value Dm1 from the signal processing unit 7 on the display unit 10 every time it is input. Therefore, the latest effective value Dm1 is displayed on the display unit 10.

  Next, a case where the operation unit 8 is operated and the AC average value Dm2 is selected as the measurement value Dm to be calculated will be described.

  At this time, the operation unit 8 outputs selection data Ds indicating this selection content (content indicating that the AC average value Dm2 is selected as the measured value Dm to be calculated) to the control unit 9. When the selection data Ds is input, the control unit 9 outputs the control signal Sc1 to control the switching state of the signal switching unit 3, thereby causing the signal switching unit 3 to perform the first measurement as the second measurement signal S2. The AC average for calculating the AC average value Dm2 for the signal processing unit 7 by outputting the signal S1 to the A / D conversion unit 6 and outputting the control signal Sc3 to execute the selection control for the signal processing unit 7. The value calculation process 60 (see FIG. 4) is started.

  In the AC average value calculation process 60, the signal processing unit 7 first executes a data cut-out process, and generates segment data in the same manner as in the effective value calculation process 50 (step 61). Next, the signal processing unit 7 executes absolute value calculation processing on each waveform data Dw included in the segment data to generate absolute value data (step 62). Subsequently, the signal processing unit 7 detects the level of the control signal Sc2 output from the determination unit 5 to determine whether or not the level is the low level (step 63). When the level is the low level, the absolute value data A windowing process is executed by applying a window function to (calculated data calculated based on the segmented data), and the processed data is generated as output data (data after the windowing process) (step 64). . If the result of determination in step 63 is that the level of the control signal Sc2 is high, absolute value data is generated as output data (data before windowing processing) without executing windowing processing.

  Next, the signal processing unit 7 calculates the moving average of the output data by executing an averaging process on the output data, and generates the average data (step 65). Subsequently, the signal processing unit 7 determines whether or not the windowing process in step 63 has been executed (step 66). When the windowing process is being executed, the average data is attenuated during the windowing process. Correction processing for correcting the minute is executed to generate an AC average value Dm2 of the measurement target signal Si (step 67). On the other hand, when the windowing process is not executed, the average data is generated as the AC average value Dm2 of the measurement target signal Si without executing the correction process. Thereby, the AC average value calculation process 60 is completed. The signal processing unit 7 outputs the generated AC average value Dm2 to the control unit 9 after the AC average value calculation processing 60 is completed.

  The control unit 9 causes the display unit 10 to display the AC average value Dm2 input from the signal processing unit 7. Thereby, the measurement of AC average value Dm2 by measuring device 1 is completed. In the measuring apparatus 1, in a state where the AC average value Dm2 is selected as the measurement value Dm to be calculated, the signal processing unit 7 repeatedly executes the AC average value calculation process 60 to obtain the AC average value Dm2 as the control unit 9. Therefore, the control unit 9 causes the display unit 10 to display a new AC average value Dm2 from the signal processing unit 7 every time it is input. Accordingly, the display unit 10 displays the latest AC average value Dm2.

  Finally, the case where the operation unit 8 is operated and the DC average value Dm3 is selected as the measured value Dm to be calculated will be described.

  At this time, the operation unit 8 outputs selection data Ds indicating this selection content (content indicating that the DC average value Dm3 is selected as the measurement value Dm to be calculated) to the control unit 9. When the selection data Ds is input, the control unit 9 outputs the control signal Sc1 to control the switching state of the signal switching unit 3, thereby causing the signal switching unit 3 to measure the measurement target signal as the second measurement signal S2. The DC average value for calculating the DC average value Dm3 for the signal processing unit 7 by outputting Si to the A / D conversion unit 6 and outputting the control signal Sc3 to execute the selection control for the signal processing unit 7. The calculation process 70 (see FIG. 5) is started.

  In the DC average value calculation process 70, the signal processing unit 7 first executes a data cut-out process, and generates segment data in the same manner as in the effective value calculation process 50 (step 71). Next, the signal processing unit 7 detects the level of the control signal Sc2 output from the determination unit 5 and determines whether or not it is at the low level (step 72). The windowing process is executed by applying a window function to each waveform data Dw to be processed, and the processed data is generated as output data (data after the windowing process) (step 73). Note that, as a result of the determination in step 72, when the level of the control signal Sc2 is high, the divided data is generated as it is as output data (data before the windowing process) without executing the windowing process.

  Next, the signal processing unit 7 calculates the moving average of the output data by executing an averaging process on the output data, and generates the average data (step 74). Subsequently, the signal processing unit 7 determines whether or not the windowing process in step 72 has been executed (step 75). When the windowing process is being executed, the average data is attenuated during the windowing process. Correction processing for correcting the minute is executed to generate the DC average value Dm3 of the measurement target signal Si (step 76). On the other hand, when the windowing process is not executed, the average data is generated as the DC average value Dm3 of the measurement target signal Si without executing the correction process. Thereby, the DC average value calculation processing 70 is completed. The signal processing unit 7 outputs the generated DC average value Dm3 to the control unit 9 after the DC average value calculation processing 70 is completed.

  The control unit 9 causes the display unit 10 to display the DC average value Dm3 input from the signal processing unit 7. Thereby, the measurement of the direct-current average value Dm3 by the measuring apparatus 1 is completed. In the measuring apparatus 1, in the state where the DC average value Dm3 is selected as the measurement value Dm to be calculated, the signal processing unit 7 repeatedly executes this DC average value calculation processing 70 to obtain the DC average value Dm3 as the control unit 9. Therefore, the control unit 9 causes the display unit 10 to display the new DC average value Dm3 from the signal processing unit 7 every time it is input. Therefore, the latest DC average value Dm3 is displayed on the display unit 10.

  Thus, the measurement apparatus 1 and the measurement method are applied when the signal processing unit 7 classifies the waveform data Dw when calculating the measurement value Dm (effective value Dm1, AC average value Dm2, and DC average value Dm3). On the basis of whether or not the fundamental wave of the signal to be measured Si is included in a certain interval or more than the reference number, if it is not included, the windowing process is not executed on the divided data or the calculated data. A measured value Dm for the measurement target signal Si is calculated based on the segment data that has not been processed. Therefore, according to the measurement apparatus 1 and the measurement method, the windowing process is performed in a state where the fundamental wave of the measurement target signal Si included in the certain section does not reach the reference number (a state less than the reference number). Since it is possible to avoid an increase in error due to the occurrence, the measured value Dm of the measurement target signal Si can be accurately measured even in such a state.

  Moreover, according to this measuring apparatus 1, the detection part 4 and the discrimination | determination part 5 are provided separately from the signal processing part 7, the detection part 4 detects the frequency (or period) of the measuring object signal Si, and the discrimination | determination part 5 Based on this frequency (or period) and the section length of the fixed section, it is determined whether or not the fundamental wave of the measurement target signal Si is included in the fixed section in the fixed section, and this determination result is used as the signal processing unit 7. (In this example, the determination result is expressed in the level of the control signal Sc2), the processing of the signal processing unit 7, that is, the processing of the DSP constituting the signal processing unit 7 is performed. As a result, it is possible to reduce the apparatus cost by using an inexpensive DSP.

  In the measuring apparatus 1, the configuration in which the signal processing unit 7 calculates the effective value Dm1 as the measured value Dm is not limited to the above configuration, that is, the configuration in which the squaring process is performed before the windowing process. For example, as shown in FIG. 6, an effective value calculation process 50 </ b> A in which a square process is performed after the windowing process may be performed. The effective value calculation process 50A is different from the already described effective value calculation process 50 in the above-described points, and thus the same processes are denoted by the same reference numerals and redundant description is omitted.

  Further, in the above-described effective value calculation processing 50, 50A, AC average value calculation processing 60, and DC average value calculation processing 70, filtering processing for noise removal is not performed on any data, but it is necessary. Depending on the above, it is possible to adopt a configuration for executing filtering processing on arbitrary data.

DESCRIPTION OF SYMBOLS 1 Measuring apparatus 4 Detection part 5 Discrimination part 7 Signal processing part Dm Measurement value Dm1 RMS value Dm2 AC average value Dm3 DC average value Dw Waveform data Si Measurement object signal

Claims (7)

The sampling data obtained by sampling the measurement target signal at a fixed sampling period is divided into fixed intervals to generate division data composed of a fixed number of the sampling data, and based on the division data and the division data A windowing process is performed on any of the calculated data before the windowing process, and a measurement value for the measurement target signal is calculated based on the data after the windowing process that has been performed. A measuring device including a signal processing unit,
Boundary error caused by performing the windowing processing a waveform number of the fundamental wave of the measurement object signal included in the prior SL constant interval becomes an error less occurring when not executing the windowing processing The number of waveforms at is defined in advance as a reference number,
The signal processing unit calculates the measurement value based on the data after the windowing process when the number of waveforms of the fundamental wave is equal to or greater than the reference number, and when the number of waveforms of the fundamental wave is less than the reference number, A measurement device that calculates the measurement value based on the data before the windowing process. A detection unit for detecting either the frequency or the period of the measurement target signal as a detection target;
A discriminator that discriminates whether or not the number of waveforms of the fundamental wave included in the certain section is equal to or larger than the reference number based on the detected object to be detected and the section length of the certain section; ,
The signal processing unit determines either the calculation of the measurement value based on the data after the windowing process or the calculation of the measurement value based on the data before the windowing process according to the determination result of the determination unit. The measuring apparatus according to claim 1.   The signal processing unit generates a calculation data by executing a square process that squares the division data, and the calculation data is generated when the number of waveforms of the fundamental wave included in the certain section is equal to or greater than the reference number. A windowing process to generate data after the windowing process and a correction process for correcting the averaging process, the opening process, and the attenuation during the windowing process for the data after the windowing process By executing, the effective value of the signal to be measured is calculated as the measured value, and when the number of waveforms of the fundamental wave included in the certain interval is less than the reference number, a windowing process is performed on the calculated data The calculation data is used as the pre-windowing data without performing the averaging process and the opening process on the pre-windowing data. Measuring apparatus according to claim 1 or 2 wherein calculating a.   When the number of waveforms of the fundamental wave included in the certain section is equal to or greater than the reference number, the signal processing unit performs windowing on the segmented data to generate the data after windowing In addition, the effective value of the measurement target signal is set as the measured value by executing a square process, an average process, an opening process, and a correction process for correcting the attenuation during the windowing process on the data after the windowing process. When the number of waveforms of the fundamental wave included in the certain interval is less than the reference number, the segment data is used as the pre-windowing data without performing the windowing process on the segment data. The measuring apparatus according to claim 1, wherein the effective value is calculated by executing the square process, the average process, and the opening process on the data before the windowing process.   The signal processing unit executes an absolute value calculation process for calculating an absolute value of the segment data and generates the calculated data, and the number of waveforms of the fundamental wave included in the certain section is equal to or greater than the reference number. In some cases, a windowing process is performed on the calculated data to generate the windowed data, an average process is performed on the windowed data, and a correction for correcting the attenuation during the windowing process By executing processing, an AC average value of the measurement target signal is calculated as the measurement value, and when the number of waveforms of the fundamental wave included in the certain section is less than the reference number, a windowing for the calculation data is performed. By performing the averaging process on the pre-windowing data as the pre-windowing data without executing the process, the AC average value is calculated. Measuring apparatus according to claim 1 or 2, wherein out.   When the number of waveforms of the fundamental wave included in the certain section is equal to or greater than the reference number, the signal processing unit performs windowing on the segmented data to generate the data after windowing And calculating the DC average value of the signal to be measured as the measured value by executing an averaging process on the data after the windowing process and a correction process for correcting the attenuation during the windowing process, and the constant value When the number of waveforms of the fundamental wave included in the section is less than the reference number, the pre-windowing data is used as the pre-windowing data without performing the windowing process on the divided data. The measurement apparatus according to claim 1, wherein the direct current average value is calculated by executing the averaging process on the measurement value. The sampling data obtained by sampling the measurement target signal at a fixed sampling period is divided into fixed intervals to generate division data composed of a fixed number of the sampling data, and based on the division data and the division data A windowing process is performed on any of the calculated data before the windowing process, and a measurement value for the measurement target signal is calculated based on the data after the windowing process that has been performed. Measuring method
The boundary is the number of waveforms of the fundamental wave with respect to the measurement target signal included in the certain section, and an error caused by executing the windowing process is equal to or less than an error generated when the windowing process is not executed. When the number of waveforms of the fundamental wave is equal to or greater than the reference number, the measured value is calculated based on the data after the windowing process, and the number of waveforms of the fundamental wave is A measurement method for calculating the measurement value based on the pre-windowing data when the number is less than the reference number.

Images