JP2003248021A - Waveform measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waveform measuring device, by which a signal processing operation and a waveform parameter measurement can be performed with high resolution and with high accuracy and by which interpolation data can be discriminated and displayed. <P>SOLUTION: In the waveform measuring device, constituted in such a way that a measurement signal waveform is converted into digital data to be written in a memory, an interpolation processing circuit used to interpolate a part between digital data is installed, and data which have been interpolated is written in the memory. A time-difference information storage part, in which when the interpolation data is discriminated, a flag bit is added to the interpolation data and in which time difference information on the trigger establishment time and a reference clock is stored at each piece of digital data converted from the measurement signal waveform and an interpolation-data-point information storage part, in which interpolation-data-point information used to interpolate adjacent digital data are stored, are installed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform measuring instrument such as a digital oscilloscope, and more particularly to processing waveform data.

[0002]

2. Description of the Related Art A digital oscilloscope, which is a typical waveform measuring instrument, converts a temporally continuous signal waveform into digital data by an A / D converter and discretely records it on a memory. Is displayed as a waveform.

Here, if the sampling frequency of the A / D converter is sufficiently higher than the resolution of the display, the signal waveform can be reproduced and displayed only by displaying the points corresponding to the discrete data. However, the sampling frequency is finite, and if the display resolution in the time axis direction called T / div is increased, the sampling frequency will decrease relative to the resolution of the display, and the signal waveform can be read from the playback display image. Becomes difficult.

In order to compensate for such a relative decrease in sampling frequency, the digital oscilloscope is provided with a function of interpolating and displaying sampled data. With this function, a waveform closer to the true signal waveform can be read from the reproduced display image of the oscilloscope.

FIG. 4 is a block diagram showing a conventional example of such a digital oscilloscope. The input circuit 1 includes an attenuator circuit, a preamplifier, etc., and adjusts the amplitude of the input signal so that it falls within an appropriate range for the input specifications of an A / D converter (hereinafter referred to as ADC) 2 and outputs it to the ADC 2.

The ADC 2 converts the input signal input from the input circuit 1 into digital data and converts it into a primary data processing circuit 3
Output to.

The primary data processing circuit 3 writes the digital data input from the ADC 2 into the primary memory 4 functioning as a buffer memory at a sample rate that matches the time axis setting. The data written in the primary memory 4 is read out to the secondary data processing circuit 5 via the primary data processing circuit 3.

The secondary data processing circuit 5 writes the data read from the primary memory 4 into the acquisition memory 6, and performs the averaging process on the data read from the acquisition memory 6 and the addition between a plurality of waveforms. Performs subtraction and multiplication. The secondary data processing circuit 5 also performs automatic measurement of waveform parameters and reading of values on the waveform designated by the cursor.

In the display processing of the data written in the acquisition memory 6, the data written in the acquisition memory 6 is read out to the interpolation processing circuit 7 via the secondary data processing circuit 5, and the read-out data is obtained. Interpolation processing is performed on the other hand.

The interpolated data is input to the display processing circuit 8. The display processing circuit 8 writes the display data in the display memory 9 and outputs the display data in the display memory 9 to an output device 10 such as a display or a printer.

As described above, the digital oscilloscope not only displays sampled data as a waveform but also has a signal processing function such as averaging and an automatic measurement function of waveform parameters. In conventional digital oscilloscopes, these functions would be based on sampled data.

FIG. 5 is an explanatory diagram of automatic period measurement in the configuration of FIG. The automatic measurement of the cycle is expected to measure the time from the point A crossing the reference line on the vertical axis to the point B crossing the reference line in the same direction based on the data read from the acquisition memory 6. The data actually sampled and stored in the acquisition memory 6 are 14 points for 2 cycles.

Although the number of data is small with respect to the resolution of the display unit, since the Nyquist frequency or more is sampled with respect to the frequency of the waveform, if the proper interpolation is performed, the waveform equivalent to the original waveform drawn by the solid line is obtained. Waveforms are displayed on the screen.

[0014]

However, in the measurement based on the acquisition data in the configuration of the conventional digital oscilloscope as shown in FIG. 4, a value finer than the time interval between actual sample points cannot be measured. As shown, an error occurs between the original period Tr and the period Tm measured by the automatic parameter measurement.

FIG. 6 is an explanatory diagram of noise removal by averaging. When the sampling data is small with respect to the resolution of the display device as in the configuration of FIG. 4, the following problems occur.

Consider a case where the noise superimposed on the signal waveform shown by the broken line in FIG. 6 is removed by averaging. A point ◯ on the waveform shown by a broken line represents data obtained by the first incorporation, and a cross represents data obtained by the second incorporation. When data is imported multiple times, the sampling points of each import have a time shift.

However, in the conventional configuration shown in FIG. 4 of the related art, since the sample points in each incorporation are averaged as data at the same time, the averaging waveform becomes a waveform indicated by a triangle point Δ and a solid line. By doing so, noise can be removed, but there is a problem in that the frequency characteristics deteriorate in the high range near the Nyquist frequency.

The present invention solves these problems, and an object of the present invention is to provide a waveform measuring instrument that can perform signal processing and waveform parameter measurement with high resolution and high accuracy.
Another object of the present invention is to make it possible to identify and display both data in a waveform measuring instrument for displaying the actually sampled data and the interpolated data in a mixed manner.

[0019]

To achieve the above object, the invention of claim 1 interpolates between digital data in a waveform measuring device configured to convert a measurement signal waveform into digital data and write the digital data in a memory. An interpolation processing circuit is provided, and the data after interpolation is written in the memory.

Thus, the interpolated data can be treated in the same manner as the digital data obtained by converting the measurement signal waveform.

According to a second aspect of the present invention, in the waveform measuring instrument according to the first aspect, means for measuring the time difference between the reference clock and the trigger is provided, and the address for writing the digital data in the memory is controlled so as to correct the time difference. Is characterized by.

As a result, it is possible to correct the time shift that occurs when the repetitive waveform is stored in the memory a plurality of times.

According to a third aspect of the present invention, in the waveform measuring instrument according to the first or second aspect, the data written in the memory is read to perform signal processing.

According to a fourth aspect of the present invention, in the waveform measuring device according to the third aspect, the data written in the memory is read out and the averaging process is performed.

According to a fifth aspect of the present invention, in the waveform measuring device according to the third aspect, a calculation between a plurality of waveforms is performed.

According to a sixth aspect of the present invention, in the waveform measuring instrument according to the first or second aspect, the waveform parameter is automatically measured based on the interpolated data written in the memory.

According to a seventh aspect of the invention, in the waveform measuring device according to the first or second aspect, the waveform data is read by designating a cursor.

With these, signal processing and measurement of waveform parameters can be performed with high accuracy.

The invention of claim 8 is characterized in that, in the waveform measuring instrument according to claim 1 or 2, waveform display processing is performed based on the interpolated data written in the memory.

According to a ninth aspect of the present invention, in the waveform measuring instrument according to the eighth aspect, the data appearance frequency is obtained based on the interpolated data written in the memory, and the brightness modulation display is performed according to the appearance frequency. And

As a result, the portion where the change in the waveform is small is displayed brightly, and the portion where the change is large is displayed darkly.
It enables waveform display that is very close to the waveform display characteristics of an analog oscilloscope.

According to a tenth aspect of the present invention, in the waveform measuring device according to any one of the first to ninth aspects, the time difference information between the trigger establishment time and the reference clock for each digital data obtained by converting the measurement signal waveform. And the interpolation data point information for interpolating between adjacent digital data are stored, and the digital data and the interpolation data in which the measurement signal waveform is converted are displayed in a distinguishable manner by referring to the time difference information and the interpolation data point information. And

According to an eleventh aspect of the invention, in the waveform measuring instrument according to any one of the first to ninth aspects, the identification flag bits are added to the interpolation data and written in the memory, and the identification flag bits are referred to. And displaying the interpolated data in a distinguishable manner.

As a result, the digital data obtained by converting the measurement signal waveform and the interpolation data can be displayed in a distinguishable manner, if necessary.

According to a twelfth aspect of the invention, in the waveform measuring device according to the tenth or eleventh aspect, only the digital data in which the measurement signal waveform is converted is read out from the interpolated data written in the memory, and different interpolation is performed. It is characterized by performing processing.

As a result, the user can confirm the optimum interpolation method according to the measurement waveform of the measurement target from the display screen.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a waveform measuring instrument showing an example of an embodiment of the present invention, and the portions common to FIG. 4 are designated by the same reference numerals. The difference between FIG. 1 and FIG. 4 is the connection position of the interpolation processing circuit 7. That is, in FIG. 1, the interpolation processing circuit 7 is connected between the primary data processing circuit 3 and the secondary data processing circuit 5. Then, the interpolated data that has been interpolated by the interpolating circuit 7 is written into the acquisition memory 6 via the secondary data processing circuit 5. As the interpolation processing circuit 7, for example, a conventionally used circuit is used.

Here, the time resolution by interpolation is not limited by the display resolution, but is set so that a resolution sufficient to improve the accuracy of the waveform parameters and the calculation between waveforms can be obtained.

The interpolated data written in the acquisition memory 6 is the interpolated data inserted by the interpolation processing circuit 7 between the digital data obtained by converting the measurement signal waveform by the ADC 2. As a result, the secondary data processing circuit 5
It is possible to treat the digital data in which the measurement signal waveform is converted and the interpolation data equally. Then, the secondary data processing circuit 5 performs moving average processing, addition / subtraction / multiplication between a plurality of waveforms, and automatic measurement of waveform parameters on the interpolated data written in the acquisition memory 6 as in the conventional case. , Read the value on the waveform specified by the cursor.

By the way, focusing on the acquisition memory 6, since the data after the interpolation is written, a storage capacity of an order of magnitude is required as compared with the case where only the digital data in which the measurement signal waveform is converted is written in the related art. Become.

Focusing on the secondary data processing circuit 5, it is necessary to perform read / write control of data with respect to the large-capacity acquisition memory 6 and various signal processing / arithmetic processing for a large amount of measurement data read from the acquisition memory 6. Therefore, a high-speed arithmetic processing function for a large amount of data is required.

The memory used as the acquisition memory 6 in the conventional waveform measuring device has a relatively small storage capacity as a single component and requires a considerable mounting space to realize a large capacity. It was difficult to increase the capacity of No. 6.

Also, as the secondary data processing circuit 5, it is difficult to obtain an appropriate arithmetic device capable of performing high speed processing on a large amount of data.

However, due to the rapid increase in the capacity of semiconductor memories and the increase in the speed of arithmetic devices in recent years, the increase in the capacity of the acquisition memory 6 and the increase in the speed of the secondary data processing circuit 5 for a large amount of data are at a feasible stage. It is becoming.

By treating the interpolation data in the same manner as the actual sampling data in this way, an effect of improving apparent resolution in the time axis direction can be obtained. As a result, signal processing, automatic measurement of waveform parameters, reading of waveform parameters by specifying the cursor, etc. can be performed with high accuracy.
The effect that it can be performed with high resolution is obtained.

Further, according to the present invention, the brightness modulation of the waveform display in the digital oscilloscope can be realized. An analog oscilloscope has a characteristic that a bright line is dark where a change in waveform is large and a bright line is displayed where there is little change. In the present invention, due to the insertion of the interpolation data, the data also exists between the actual sampling points. This makes it possible to obtain the frequency of appearance of a value near the voltage value of one data point in the vicinity of one data point in the waveform data after interpolation including the interpolation data. In the conventional configuration shown in FIG. 4, when the time axis is expanded, the number of data items on the display is reduced, and it is difficult to obtain the appearance frequency.

By obtaining the appearance frequency, the point can be displayed on the screen with brightness according to the appearance frequency.
By adding such processing, a portion where the change in waveform is small is displayed brightly and a portion where the change is large is displayed darkly, and a waveform display very close to the waveform display characteristic of the analog oscilloscope can be obtained.

FIG. 2 is a block diagram showing another embodiment, in which the same parts as those in FIG. 1 are designated by the same reference numerals. In FIG. 2, the trigger circuit 11 is added to the configuration of FIG.
The reference clock circuit 12 and the time measuring circuit 13 are provided, and the function of measuring the time difference between the reference clock and the trigger is added.

The circuit configuration of FIG. 2 is also effective for noise removal by averaging. In the apparatus of FIG. 2, the data whose time resolution has been improved by the interpolated data is corrected for the time difference, and the averaging is performed. The output signals of the trigger circuit 11 and the reference clock circuit 12 are input to the time measuring circuit 13, and the time measuring circuit 13 measures the time difference between the reference clock and the trigger. Based on the measurement result of the time measuring circuit 13, the address taken into the primary memory 4 is controlled so that the positions of the sampling data on the time axis in each taking match.

As a result, the bandwidth is not limited and
Averaging processing that can remove noise can be realized.

Although the primary memory and the acquisition memory are shown as independent in the embodiment, the physically integrated memory may be functionally divided and used properly.

FIG. 3 is also a block diagram showing another embodiment. In FIG. 3, the secondary data processing circuit 5 in the configuration of FIG. 2 is adjacent to a time difference information storage unit 51 that stores time difference information between a trigger establishment time and a reference clock for each digital data whose measurement signal waveform is converted. An interpolated data point number information storage unit 52 for storing interpolated data point number information for interpolating between digital data to be processed is provided.

The configuration shown in FIG. 3 works effectively when it is desired to distinguish between the digital data obtained by converting the measurement signal waveform and the interpolation data. For example, in displaying only the digital data in which the measurement signal waveform is converted, the acquisition memory 6 is based on the time difference information between the trigger establishment time and the reference clock stored in the time difference information storage unit 51.
The digital data obtained by converting the actually sampled measurement signal waveform when the trigger is satisfied is searched from the data stored in. Subsequently, the number of interpolation data points existing between the actually sampled data is obtained from the interpolation data point number information storage unit 52, and only the data separated by the number of points are extracted.

On the other hand, in displaying only the interpolated data, the data stored in the acquisition memory 6 based on the time difference information between the trigger establishment time and the reference clock stored in the time difference information storage unit 51. From among the digital data obtained by converting the actually sampled measurement signal waveform when the trigger is established. Subsequently, the number of interpolation data points existing between the actually sampled data may be obtained from the interpolation data point number information storage unit 52, and the data separated by that number may not be taken out.

In order to identify and display the digital data and the interpolated data in which the measurement signal waveform is converted, an identification flag bit is added to the interpolated data and written in the memory instead of the configuration of FIG. The flag bit for use may be referred to.

Further, by reading only the digital data in which the measurement signal waveform is converted from the interpolated data written in the memory, different interpolation processing such as sin interpolation, linear interpolation, pulse interpolation can be performed, and the user can From the display screen, you can check the optimal interpolation method according to the measured waveform of the measurement target.

According to the present invention, when the set ratio of the data length and the observation time (data length / observation time) is larger than the maximum sampling frequency of the A / D converter, the interpolation operation is performed, and the interpolated data is stored in the memory. By writing, the interpolation data and the measurement data are treated equally.

As a result, automatic measurement of waveform parameters such as period and time difference and reading of waveform parameters by cursor designation can be performed with high precision and high resolution.

Further, by utilizing the interpolation data as frequency information in the waveform display without distinguishing it from the original sample data, it is possible to apply a luminance modulation like an analog oscilloscope to the display waveform even for a high speed signal.

Further, by providing a circuit for measuring the time difference between the trigger and the sampling and rearranging the waveform data after interpolation by the trigger time reference, the bandwidth of the averaging process can be improved.

Further, it is possible to distinguishably display the digital data in which the measurement signal waveform is converted and the interpolation data, if necessary.

Further, by reading only the digital data in which the measurement signal waveform is converted from the interpolated data written in the memory, different interpolation processing is performed and the optimum interpolation method according to the measurement waveform of the measurement object is displayed. Can be visually confirmed on the screen.

[0063]

As described above, according to the present invention,
It is possible to provide a waveform measuring instrument that can perform signal processing and waveform parameter measurement with high resolution and high accuracy, and is suitable for various waveform measuring instruments including a digital oscilloscope.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a conventional waveform measuring device.

FIG. 5 is an explanatory diagram of automatic measurement of a cycle.

FIG. 6 is an explanatory diagram of a conventional averaging waveform.

[Explanation of symbols] 1 input circuit 2 A / D converter 3 Primary data processing circuit 4 Primary memory 5 Secondary data processing circuit 51 Time difference information storage 52 Interpolation data point information storage unit 6 secondary memory 7 Interpolation processing circuit 8 Display processing circuit 9 Display memory 10 Output device 11 Trigger circuit 12 Reference clock circuit 13 hour measuring circuit

Claims (12)

[Claims] 1. A waveform measuring instrument configured to convert a measurement signal waveform into digital data and write the digital data into a memory, wherein an interpolation processing circuit for interpolating between digital data is provided, and the data after the interpolation is written into the memory. Waveform measuring device characterized by. 2. A waveform measuring instrument according to claim 1, further comprising means for measuring a time difference between the reference clock and the trigger, and controlling an address for writing the digital data in the memory so as to correct the time difference. 3. The waveform measuring instrument according to claim 1, wherein the data written in the memory is read out and signal processing is performed. 4. The waveform measuring instrument according to claim 3, wherein the data written in the memory is read out and averaged. 5. The waveform measuring instrument according to claim 3, wherein an operation between a plurality of waveforms is performed based on the interpolated data written in the memory. 6. The waveform measuring device according to claim 1, wherein the waveform parameter is automatically measured based on the interpolated data written in the memory. 7. The waveform measuring device according to claim 1, wherein the waveform data is read by designating a cursor based on the interpolated data written in the memory. 8. The waveform measuring device according to claim 1, wherein the waveform display process is performed based on the interpolated data written in the memory. 9. The waveform measuring device according to claim 8, wherein a data appearance frequency is obtained based on the interpolated data written in the memory, and luminance modulation display is performed according to the appearance frequency. 10. The time difference information between the trigger establishment time and the reference clock and the interpolation data point number information for interpolating between adjacent digital data are stored for each digital data in which the measurement signal waveform is converted, and the time difference information and the interpolation data are stored. The waveform measuring instrument according to any one of claims 1 to 9, wherein the digital data obtained by converting the measurement signal waveform and the interpolation data are displayed in a distinguishable manner with reference to the score information. 11. The interpolation data is added with an identification flag bit and written in a memory, and the interpolation data is displayed in a distinguishable manner with reference to these identification flag bits. The waveform measuring instrument according to any one. 12. The method according to claim 1, wherein only the digital data in which the measurement signal waveform is converted is read out from the interpolated data written in the memory, and different interpolation processing is performed.
0 or the waveform measuring device according to claim 11.