JP5540959B2 - Waveform measuring device - Google Patents

Description

  The present invention relates to a waveform measuring apparatus that measures a time width at a predetermined location from a waveform of an input electric signal.

  Waveform measuring devices such as oscilloscopes and digital wattmeters are devices that enable observation of electrical signals. Usually, these waveform measuring apparatuses are provided with a cathode ray tube, a liquid crystal display, and the like, and an electric signal (input signal) input from an electric circuit or the like to be measured is displayed on the screen as waveform data. The screen display at this time has a format in which the horizontal axis represents time, and the vertical axis represents voltage or current.

  Recent waveform measuring apparatuses have a so-called cursor measurement function. The cursor measurement function is a function for automatically measuring parameters such as time at the position by moving the cursor displayed on the screen to an arbitrary position of the waveform data by a key operation. Thereby, the user can save the trouble of reading the parameters from the scale on the screen. For example, it is possible to measure a time difference and a frequency between time cursors using two time cursors orthogonal to a horizontal axis (time axis) representing time (Patent Document 1). In general oscilloscopes, it is also possible to measure the potential difference between the voltage cursors using two voltage cursors orthogonal to the vertical axis (voltage axis) representing the voltage.

JP-A-6-50993

  However, in the cursor measurement function of the oscilloscope as described in Patent Document 1, when there are a plurality of portions where the time width is to be measured on the waveform data, it is necessary to move and align the time cursor for each of the plurality of portions. is there. Therefore, measuring all locations is a laborious operation.

  The time cursor is used for designating time by an operator's operation. For this reason, it is difficult to position the time cursor and to measure the frequency during the acquisition (during the acquisition operation) in which the waveform changes one after another with the passage of time.

  The present invention has been made in view of such problems, and an object thereof is to provide a waveform measuring apparatus that can easily measure time widths at a plurality of locations even from waveform data being acquired.

  In order to solve the above problems, a typical configuration of a waveform measuring apparatus according to the present invention includes a sampling data acquisition unit that discretizes an input signal at a predetermined interval to acquire sampling data, and a voltage from the sampling data. A waveform data acquisition unit for acquiring waveform data, a threshold setting unit for setting a predetermined voltage value on the voltage axis of the waveform data as a threshold, and times of a plurality of passing points that pass the threshold on the waveform data are measured. , A time width calculation unit for calculating the time width of the peak or valley of the waveform data from the time between a plurality of passing points, a waveform data, a threshold cursor indicating the threshold value, and a time width of the peak or valley And a display unit.

  If it is the said structure, the time width of the several peak part or trough part of waveform data can be measured only by setting the threshold value of one voltage value, and the measurement result can be displayed. In other words, it is possible to display the time widths at a plurality of locations on the waveform data only by the user once operating the threshold cursor. In the above configuration, since the measurement can be performed instantaneously, the time width of peaks and valleys can be displayed even from waveform data during acquisition (during the acquisition operation) where the waveform changes one after another. is there.

  The threshold setting unit sets a predetermined voltage value different from the threshold as the second threshold, and the time width calculation unit measures the times of the plurality of second passing points that pass the second threshold on the waveform data, The time width between the passing point and the second passing point may be further calculated from each time of the passing point and the second passing point, and the display unit may further display the time width between the passing point and the second passing point.

  According to the said structure, the rise time and fall time of a peak part and a trough part can be measured. Therefore, more detailed analysis of the waveform data becomes possible.

  The threshold value may be calculated using a Schmitt circuit in which the output changes with hysteresis with respect to the voltage change. The Schmitt circuit is an input method in which two values of a high value and a low value are provided as threshold values, and an output is switched when an input signal passes through these two threshold values. With this configuration, the output is not switched only by passing through one of the high and low thresholds, so that it is possible to prevent the influence of chattering noise of the input signal and improve the measurement accuracy.

  The waveform data acquisition unit acquires two or more different waveform data on the same time axis, the threshold value setting unit sets a threshold value for each of the different waveform data, and the time width calculation unit is for each of the different waveform data The time points of the passing points may be measured to further calculate the time widths of the passing points on the different waveform data, and the display unit may further display the time widths of the passing points on the different waveform data.

  According to the above configuration, various parameters of different waveforms can be compared, and the relationship between waveform data such as response time and rise time can be analyzed in more detail.

  The time width calculation unit may ignore a passing point within a predetermined time from a predetermined timing or ignore a passing point after a predetermined time has elapsed. As a result, for example, even from an input signal having an interval (between bursts) in which no pulse appears, such as a burst wave, it is possible to ignore only the burst and measure only the pulse display. As an opposite example, it is also possible to measure only between bursts and ignore the pulse display. In this way, the time width of only the target location can be measured even from an input signal in which a complicated pulse train repeatedly appears.

  According to the present invention, it is possible to provide a waveform measuring apparatus capable of easily measuring time widths at a plurality of locations even from waveform data being acquired.

It is a block diagram which illustrates schematic structure of the waveform measuring device concerning this embodiment. It is a figure which illustrates the image display by the screen part of FIG. It is a flowchart explaining the cursor measurement function in acquisition. It is a figure explaining the threshold value computed using the Schmitt circuit. It is a figure explaining the 1st other measurement mode of the cursor measurement function of a waveform measuring device. It is a figure explaining the 2nd other measurement mode of the cursor measurement function of a waveform measuring device. It is a figure explaining the 3rd other measurement mode of the cursor measurement function of a waveform measuring device.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(Waveform measurement device)
FIG. 1 is a block diagram illustrating a schematic configuration of a waveform measuring apparatus 100 according to this embodiment. A waveform measuring apparatus 100 shown in FIG. 1 is an apparatus that measures the waveform of an electric signal flowing through a measurement target such as an electric circuit. Specifically, the time difference (time width) and voltage at predetermined locations in the waveform of the electric signal can be measured. Examples of such waveform measuring apparatuses include various oscilloscopes and digital wattmeters. In the present embodiment, for ease of understanding, description will be made assuming that the waveform measuring apparatus 100 is a digital oscilloscope.

  First, an electrical signal flowing through the measurement target is input to the waveform measurement apparatus 100 (input signal) via a probe (not shown) and guided to the sampling data acquisition unit 102. The sampling data acquisition unit 102 discretizes an input signal at a predetermined interval and acquires sampling data. The sampling data acquisition unit 102 includes an attenuator 104 (attenuator), a preamplifier 106 (amplifier), and an A / D converter 108. The attenuator 104 and the preamplifier 106 adjust the input signal to an appropriate amplitude, and the A / D converter 108 discretizes the input signal at a predetermined sampling rate.

  The waveform data acquisition unit 110 located after the sampling data acquisition unit 102 acquires the waveform data L1 (see FIG. 2) from the obtained sampling data. The waveform data acquisition unit 110 includes a data processing circuit 112 and an acquisition memory 114. The data processing circuit 112 converts the sampling data into waveform data L1 indicating the relationship between time and voltage. The acquisition memory 114 is a storage medium that enables a series of operations (acquisition) that repeats acquisition and display of waveform data. Sampling data is temporarily stored and processed through the data processing circuit 112.

  The control unit 116 includes a CPU 118 that is an integrated circuit, a main storage memory 120 that is a storage medium, and the like, and manages and controls the entire waveform measuring apparatus 100. The CPU 118 comprehensively controls each part such as the waveform data acquisition unit 110 by executing a predetermined program. The main memory 120 is composed of ROM, RAM, EEPROM, nonvolatile RAM, flash memory, HDD, and the like, and stores programs executed by the CPU 118 and the like. In the present embodiment, a threshold setting unit 122 and a time width calculation unit 124 used for a cursor measurement function described later are realized in the CPU 118 by a program.

  The waveform data acquired by the waveform data acquisition unit 110 is displayed to the outside by the display unit 126. The display unit 126 includes a display processing circuit 128 and a screen unit 130. The display processing circuit 128 includes a display memory (not shown), and the waveform data L1 (see FIG. 2) is temporarily stored in the display memory, subjected to image processing and the like, and then output to the screen unit 130. Is done. The screen unit 130 is configured by a cathode ray tube, a liquid crystal display, or the like, and displays the waveform data L1 as an image.

  FIG. 2 is a diagram illustrating image display by the screen unit 130 of FIG. The waveform data L1 shown in FIG. 2 is swept from the left to the right on the screen unit 130 at a constant speed (for example, 2 us / div). At this time, the time axis T1 indicates a time with respect to a predetermined trigger point (starting point of the sweep) (the past time on the left side in the figure), and the voltage axis V1 indicates a voltage value at the predetermined time. As a result, the user can observe the relationship between time and voltage in the waveform data L1.

(Cursor measurement function)
The waveform measuring apparatus 100 according to the present embodiment has a cursor measurement function. FIG. 3 is a flowchart for explaining the cursor measurement function during acquisition. Here, the screen display shown in FIG. 2 exemplifies a case where the cursor measurement function is effective. In this case, the waveform display image 132 displaying the waveform data L1 is displayed at the upper part and the measurement by the cursor measurement function is performed at the lower part. A measurement result display image 134 representing the result is displayed. In particular, the cursor measurement function of the waveform measuring apparatus 100 can display the measurement result in synchronization with the acquisition. Hereinafter, the waveform measuring apparatus 100 of FIG. 1 will be further described with reference to FIGS. 2 and 3.

  When the cursor measurement function is valid, first, in step 200 of FIG. 3, a threshold cursor C1 displayed on the waveform display image 132 is set. The threshold cursor C1 (see FIG. 2) is a horizontal axis cursor indicating a predetermined voltage value on the voltage axis V1, and can be moved to an arbitrary position on the voltage axis V1 by a key operation by the user. When the threshold cursor C1 is moved, the threshold setting unit 122 (see FIG. 1) sets the voltage value indicated by the threshold cursor C1 as the threshold. When the threshold cursor C1 is not moved (the threshold is not reset), the previously set voltage value (previous value) is acquired as the threshold.

  Next, in step 202, the user sets display items to be displayed on the measurement result display image 134 (see FIG. 2). Various display items can be switched depending on the measurement mode. For example, it is possible to display the time widths of the peaks and valleys of the waveform, and to display the rise time width or fall time width of the peaks and valleys. If the display item setting is not changed, the previous setting (previous value) is acquired.

  In step 204, the waveform of the input signal is captured by the sampling data acquisition unit 102 and the waveform data acquisition unit 110. The waveform acquisition is performed by repeatedly measuring the voltage value of the input signal at several MHz (depending on the specifications and settings of the apparatus) and storing it in a cache memory (not shown). The acquired waveform is stored in the acquisition memory 114 (step 206), and is displayed on the waveform display image 132 (see FIG. 2) as the waveform data L1 by the display unit 126 (step 208).

  In step 210, it is determined whether a predetermined time has elapsed. The predetermined time is an interval for displaying (or updating the display of) each time width of the waveform, and can be set to a time that does not hinder the observation by the user, for example, about 5 seconds.

  If the predetermined time has elapsed (Yes in step 210), in the following step 212, the time width calculation unit 124 extracts the intersection of the threshold value and the waveform based on the waveform stored in the acquisition memory. This threshold value corresponds to the threshold cursor C1 shown in FIG. 2, and the waveform corresponds to the waveform data L1. The intersection points correspond to a plurality of passing points (P0 to P10) passing through the threshold cursor C1 on the waveform data L1. Then, the time width calculation unit 124 measures the time of the extracted intersection (passing point), and calculates each time width from the time (step 214).

  In step 216, as shown in FIG. 2, the display unit 126 displays a measurement result of each time width as a measurement result display image 134 in a GUI (Graphical User Interface). In the measurement result display image 134, various measurement results at the passing points P0 to P10 are displayed in order from above. Time is the time of the passing point (time with respect to a predetermined trigger point). Slope represents whether the passing point is located on the rising slope or the falling slope in the direction of the arrow.

  + Width, -Width, and Period are time widths calculated from the time between the passing points by the time width calculation unit 124 on the waveform data L1. If the distance between adjacent passing points is a peak, the time width is displayed in + Width, and if it is a valley, the time width is displayed in -Width. For example, in the waveform display image 132, the interval between the passing point P0 and the passing point P1 is a peak + W1, and the time width is displayed in the item + Width of the passing point P1. Further, for example, in the waveform display image 132, the interval between the passing point P1 and the passing point P2 is valley-W2, and the time width is displayed in the item -Width of the passing point P2. Period is a period and is calculated by combining the time widths of adjacent peaks and valleys. For example, in the Period item of the passing point P2, a time width ΔT1 between the passing point P0 and the passing point P2 in the waveform display image 132 is displayed.

  Refer to FIG. 3 again. After the measurement result is displayed in step 216 or after No in step 210, it is determined in step 218 whether or not to capture the next waveform. In the case of Yes in Step 218, the process returns to Step 204 and the measurement of the time width is continued together with the acquisition. In the case of No in Step 218, the waveform acquisition is finished.

As described above, in the cursor measurement function of the waveform measuring apparatus 100, the user only operates the threshold cursor C1 on the waveform display image 132 once, and a plurality of locations on the waveform data L1 are synchronized with the acquisition. The time width can be displayed on the measurement result display image 134.

  Here, in the present embodiment, the control unit 116 determines whether or not the peak and valley of the waveform data L1 exceed the threshold value. However, if chattering noise occurs in the input signal near the threshold and the waveform fluctuates up and down, it may be determined that the chattering noise is also a peak or valley. Therefore, in this embodiment, the threshold value is calculated using a Schmitt circuit in which the output changes with hysteresis with respect to a change in voltage.

  FIG. 4 is a diagram illustrating the threshold value A1 calculated using a Schmitt circuit. In FIG. 4, the input signal is expressed as a sequence of plots for convenience. The Schmitt circuit is an input method in which two values of a high value and a low value are provided as threshold values, and an output is switched when an input signal passes through these two threshold values. The threshold value A1 illustrated in FIG. 4 includes a high threshold value A1H and a low threshold value A1L. In the case of the threshold value A1 of this configuration, the output is not switched only by the input signal passing either the high threshold value A1H or the low threshold value A1L, and the previous output state is maintained. That is, amplitude noise that is equal to or less than the hysteresis width of the threshold A1 (the width between the low threshold A1L and the high threshold A1H) can be ignored. Therefore, the influence of chattering noise on the input signal can be prevented and the measurement accuracy can be improved.

  As described above, according to the waveform measuring apparatus 100 according to the present embodiment, a plurality of peaks (for example, peaks + W1) or valleys (for example, valleys) of the waveform data L1 can be obtained simply by setting a threshold value for one voltage value. Part-W2) can be accurately measured and the measurement result can be displayed. Further, in the above configuration, since the voltage value can be used as a threshold value, measurement can be performed instantaneously. Therefore, even from the waveform data L1 during acquisition (during the acquisition operation) in which the waveform changes one after another, The time width of the valley can be displayed in real time.

(First other measurement mode of cursor measurement function)
FIG. 5 is a diagram for explaining a first other measurement mode of the cursor measurement function of the waveform measuring apparatus 100. In this measurement mode, it is possible to measure the rise time and fall time of the peak and valley of the waveform data. Hereinafter, description will be made with reference to the screen example of FIG. 5 and a part of the flowchart of FIG. Note that setting (display switching) to the display item corresponding to the measurement mode can be performed in step 202 shown in FIG. 3, and depending on the measurement mode, step 200 is moved to the subsequent stage of step 202. It is possible.

  As shown in FIG. 5, in this mode, a second threshold cursor C2 is displayed on the waveform display image 132 in addition to the threshold cursor C1. The threshold value setting unit 122 sets a predetermined voltage value indicated by the threshold value cursor C2 as a second threshold value that is different from the threshold value indicated by the threshold value cursor C1 (step 202). Then, the time width calculation unit 124 measures the times of a plurality of second passing points (such as Q2) that pass the second threshold on the waveform data L2, and passes through the passing point (such as P0) and the second passing point (such as Q2). ) To further calculate the time width (ΔT2 to ΔT6) between the passing point and the second passing point (step 214).

  The calculated time width is displayed by the display unit 126 as a rise time (Rise) or a fall time (Fall) (step 216). For example, the waveform display image 132 has a falling slope between the passing point P1 and the second passing point Q2, and the time width ΔT2 is displayed in the Fall item of the second passing point Q2 of the measurement result display image 134.

  Thus, in this measurement mode, the rise time and fall time of the peaks and valleys can be easily measured. Therefore, more detailed analysis of waveform data is possible. Note that the second threshold value may also be calculated using a Schmitt circuit in the same manner as the threshold value A1 in FIG. 4, thereby improving measurement accuracy.

(Second other measurement mode of cursor measurement function)
FIG. 6 is a diagram for explaining a second other measurement mode of the cursor measurement function of the waveform measuring apparatus 100. In this measurement mode, the time width between different waveform data can be measured. Hereinafter, description will be made with reference to the screen example of FIG. 6 and a part of the flowchart of FIG.

  As shown in FIG. 6, in this mode, the waveform data acquisition unit 110 can acquire two or more different waveform data (waveform data L3 and waveform data L4) on the same time axis T1. The threshold setting unit 122 sets a threshold based on the position of the threshold cursor C1 or the threshold cursor C2 for each of the waveform data L3 and the waveform data L4 (step 200). Then, the time width calculation unit 124 measures the time of each passing point (passing point P0 or the like or passing point R1 or the like) of the waveform data L3 and the waveform data L4, and further calculates the time width of the passing point on different waveform data. (Step 214).

  The calculated time width is displayed together with the waveform data distinction (Line) by the display unit 126 (step 216). For example, in the waveform display image 132, a time width ΔT7 between the passing point P0 on the waveform data L3 and the passing point R1 on the waveform data L4 is calculated, and the measurement result is the row of the passing point R1 in the measurement result display image 134. To display.

  As described above, in this measurement mode, it is possible to compare various parameters of different waveforms and analyze the relationship between waveform data such as response time and rise time in more detail.

(Third other measurement mode of cursor measurement function)
FIG. 7 is a diagram for explaining a third other measurement mode of the cursor measurement function of the waveform measuring apparatus 100. In this measurement mode, it is possible to measure the time width of only the target location from the waveform data. Hereinafter, description will be made with reference to the screen example of FIG. 7 and a part of the flowchart of FIG.

  As shown in FIG. 7, in this mode, the time width calculation unit 124 can ignore passing points within a predetermined time from a predetermined timing (trigger point) in step 212. Conversely, it is also possible to obtain a passing point within a predetermined time and ignore the passing point after the predetermined time has elapsed.

  For example, the waveform data L5 in FIG. 7 is a burst wave having a section in which no pulse appears (interburst D1), but in this mode, it can be ignored without calculating the time width using the interburst D1 as a hold section. . Then, the time width ΔT9 including the pulse display D2 and the time width of each pulse included in the pulse display D2 are calculated from the passing points after the pulse display D2 (not shown to avoid complication in the waveform display image 132). (Step 214), the measurement result is displayed (Step 216). In contrast to this, it is also possible to measure only the time width ΔT8 of the interburst D1 and ignore the pulse display D2 to the pulse display D4.

  As described above, in this measurement mode, even from an input signal in which a complicated pulse train repeatedly appears, it is possible to measure a time width only at a target location.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention can be used for a waveform measuring apparatus that measures a time width at a predetermined location from a waveform of an input electrical signal.

C1, C2 ... threshold cursor, L1 to L5 ... waveform data, A1 ... threshold, A1H ... threshold, A1L ... threshold, D1 ... between bursts, D2 to D4 ... pulse display, P0 to P10, R1 to R8 ... passing point, Q2 , Q3, Q6, Q7, Q10: second passing point, ΔT1 to ΔT11: time width, 100: waveform measuring device, 102: sampling data acquisition unit, 104: attenuator, 106: preamplifier, 108: D converter, 110 ... Waveform data acquisition unit, 112 ... Data processing circuit, 114 ... Acquisition memory, 116 ... Control unit, 120 ... Main memory, 122 ... Threshold setting unit, 124 ... Time width calculation unit, 126 ... Display unit, 128 ... Display processing circuit , 130 ... Screen section, 132 ... Waveform display image, 134 ... Measurement result display image

Claims (4)

A sampling data acquisition unit that discretizes an input signal at a predetermined interval to acquire sampling data;
A waveform data acquisition unit for acquiring voltage waveform data from the sampling data;
A threshold value setting unit for setting a predetermined voltage value on the voltage axis of the waveform data as a threshold value;
A time width calculation unit that measures the time of each of a plurality of passing points that pass through the threshold value on the waveform data, and calculates a time width of a peak portion or a trough portion of the waveform data from the time between the plurality of passing points; ,
In the waveform measuring apparatus comprising the waveform data, a threshold cursor indicating the threshold, and a display unit that displays a time width of the peak or valley ,
The threshold setting unit sets a predetermined voltage value different from the threshold as the second threshold,
The time width calculator measures the times of a plurality of second passage points that pass through the second threshold on the waveform data, and determines the passage points and the time points from the times of the passage points and the second passage points. Further calculate the time width of the second passing point,
The waveform measuring apparatus , wherein the display unit further displays a time width between the passing point and the second passing point . The waveform measurement apparatus according to claim 1 , wherein the threshold value is calculated using a Schmitt circuit whose output changes with hysteresis with respect to a change in voltage. The waveform data acquisition unit acquires two or more different waveform data on the same time axis,
The threshold setting unit sets a threshold for each of the different waveform data,
The time width calculator measures the time of each passing point on the different waveform data, and further calculates the time width of the passing point on the different waveform data,
The waveform measuring apparatus according to claim 1, wherein the display unit further displays a time width of a passing point on the different waveform data. The time width calculating unit ignores the passing point within a predetermined time from a predetermined timing, or claims 1, characterized in that ignoring the passing point after a predetermined time in any one of claims 3 The waveform measuring apparatus described.

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