JP2003315367A - Waveform measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waveform measuring device capable of measuring a glitch wherein a peak is positioned between sampling points of ADC without changing the ADC. <P>SOLUTION: This waveform measuring device has a constitution wherein a continuous input signal waveform is sampled at prescribed intervals, and the sampling data are taken into an acquisition memory, and then the sampling data are read out and displayed as a waveform on a display screen. The measuring device has also a constitution wherein a peak value of the glitch is detected by differentiating the input signal waveform and comparing it with a reference value, and the peak value is inserted between data of the sampling data and displayed. <P>COPYRIGHT: (C)2004,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 improving waveform capturing and recording.

[0002]

2. Description of the Related Art A digital oscilloscope, which is a well-known typical waveform measuring instrument, converts a time-continuous signal waveform into digital data by an analog-digital converter (hereinafter abbreviated as ADC), The data is discretely accumulated in the memory, and the accumulated data is displayed as a waveform.

FIG. 2 is a block diagram showing an example of such a conventional waveform measuring instrument. 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 with respect to the input specifications of the ADC 2, and outputs it to the ADC 2. The ADC 2 converts the input signal into digital data.

The output data of the ADC 2 is converted by the primary data processing circuit 3 into a sample rate suitable for the time axis setting and written in the primary memory 4.

On the other hand, when the input waveform satisfies the desired condition set by the observer (this is called triggering),
A signal indicating that the trigger condition is satisfied is sent from the trigger circuit 5 to the primary data processing circuit 3.

After the trigger condition is satisfied, the data of the required number of samples is collected on the time axis after the trigger point, and the data written in the primary memory 4 is set in the secondary data processing circuit 6. The signal is processed and written in the acquisition memory 7.

Next, the data written in the acquisition memory 7 is guided to the display processing circuit 8 via the secondary data processing circuit 6 and stored in the display memory 9 from there.
Finally, the display processing circuit 8 reads out the data stored in the display memory 9 and sends it to the output device 10. Output device 1
As 0, an LCD external monitor, a printer or the like is used.

[0008]

By the way, in the digital oscilloscope, the signal waveform is converted into digital data by the ADC 2 and is used for recording / display. For this reason, the maximum value of the sampling rate is limited to the upper limit of the conversion speed of the ADC.

Signal waveforms to be measured in today's digital oscilloscopes include many input / output signals of CPUs, memories, and other logic circuits. A steep pulse-like abnormal signal called a glitch may be mixed into these input / output signals. The abnormal signal is generated due to an error in the propagation delay time on the circuit, and often causes a malfunction. Therefore, the ability to detect the presence of glitches is one of the performances required of a digital oscilloscope.

Here, an example in which the above-mentioned limitation of the sampling rate becomes a problem in the glitch waveform measurement will be given. FIG. 3 is a schematic diagram of a rising waveform of a logic signal, and is a waveform diagram when a glitch exists immediately before the rising waveform.

In the figure, points indicated by circles are sampling points in the ADC 2. If there is a glitch peak between the sampling points, the displayed waveform on the oscilloscope screen will look like a broken line. However, here, in order to make it easier to distinguish the actual waveform (solid line) from the broken line, the broken line is displayed below the solid line. Actually, a solid line passing through the center of the circle and a broken line passing through the lower end of the circle are displayed at overlapping positions.

Therefore, in the conventional waveform measuring device, for a waveform having such a glitch, even if the logic signal can be accurately reproduced on the screen of the oscilloscope, it is not possible to know the existence of the glitch. There were challenges. Further, if the sampling rate at this time is the highest sampling rate of this ADC, there is a problem that detection of this glitch becomes extremely difficult.

Further, within the scope of the prior art, in order to capture such a signal, an ADC having a higher sampling rate is used, or a repetitive waveform is equivalently sampled (equivalently, the sampling rate is increased). Whether to record. However, the high-speed ADC is very costly, and its adoption is often difficult considering the total cost of the product. Further, since the glitch itself does not always appear repeatedly, there is a problem that there is no guarantee that it can be captured by equivalent time sampling.

An object of the present invention is to solve the above-mentioned problems, and to provide a waveform measuring device which enables measurement of a glitch such that a peak appears between sampling points of an ADC without changing the ADC. To do.

[0015]

In order to achieve such an object, the invention of claim 1 samples a continuous input signal waveform at a predetermined interval, stores the sampled waveform data in an acquisition memory, and thereafter In a waveform measuring instrument configured to read out this sampling waveform data and display it as a waveform on a display screen, the peak value of the glitch is detected by differentiating the input signal waveform and comparing it with a reference value, and the peak value is detected. It is characterized in that the sampling waveform data is inserted between the data and displayed.

With such a configuration, the presence of the glitch can be detected in an analog manner, and only its peak value can be read. This peak value is inserted and displayed between the data of the original sampling points. As a result, the glitch superimposed on the input signal waveform can be reliably captured and displayed.

In this case, a differentiating circuit for differentiating the input signal waveform, a comparing circuit for comparing the output of the differentiating circuit with zero voltage and two positive and negative voltages as reference values, and the input. A sample hold circuit for sampling and holding a signal waveform, detecting the presence of a glitch when the output signal of the differentiating circuit passes through the three reference values, and the input signal when the output value of the differentiating circuit is zero The waveform value can be held in the sample hold circuit as a glitch peak value.

Incidentally, depending on the magnitude of the positive and negative reference values among the above three reference values, not only a steep glitch but also a peak value of a waveform having a less steep peak can be captured.

Further, in this case, the time relation between the time when the glitch is detected and the sampling data is obtained when the presence of the glitch is detected, and the sampling of the acquisition memory corresponding to the time relation is performed. The glitch peak value is transferred to the data area.

A low-speed analog-to-digital converter can be used as the analog-to-digital converter for converting the data held in the sample-hold circuit into digital data.

[0021]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a waveform measuring device according to the present invention. The same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, a portion different from FIG. 2 is a portion surrounded by a chain line. The differentiating circuit 11 differentiates the signal waveform output from the input circuit 1. The comparison circuit 12 compares the output voltage of the differentiation circuit 11 with a predetermined voltage level. A sample hold circuit (hereinafter abbreviated as S / H circuit) 13 samples and holds the output signal of the input circuit 1 based on the signal from the comparison circuit 12.

The low speed ADC 14 digitally converts the hold signal of the S / H circuit 13. Memory 15 is low speed ADC1
The output data of 4 is stored.

Next, the operation of each section will be described. Differentiator circuit 1
The waveform differentiated by 1 is input to the comparison circuit 12, and glitch detection is performed by voltage level comparison. The glitch detection method will be described below.

Since the glitch has a steep pulse waveform as shown in FIG. 3 above, the differential waveform around the peak thereof passes through the point where the positive relatively large voltage value is zero and the voltage is zero when the glitch is convex upward. As a result, the waveform is such that it passes almost linearly to a relatively large negative voltage value. If the glitch is convex downwards,
This is the opposite relationship.

Therefore, in the comparison circuit 12, the differential waveform to be input passes from a positive value (positive reference value) to the voltage zero point (zero reference value) and then to a negative value (negative reference value). The glitch can be detected if it is possible to detect the continuous passage of the light (conversely, it is possible even in the case of negative → zero → positive). Such a comparison circuit can be realized, for example, by using a comparator or the like to monitor the voltage at the zero point and at the other two positive and negative points.

When a glitch is detected, the comparison circuit 12
Instructs the S / H circuit 3 to enter the hold state when the voltage zero point is passed. This holds the voltage value at the peak of the glitch. When a predetermined negative value after passing the zero point is passed, the primary data processing circuit 4 is also notified of glitch detection, and further the low speed ADC 14 is instructed to perform analog / digital conversion.

The value converted into digital data by the low speed ADC 14 is held in the memory 15. On the other hand, the primary data processing circuit 3a that has received the notification of glitch detection determines the time relationship (or the positional relationship in the memory) between the time when the glitch is detected and the data recorded by normal sampling.

When data collection by normal sampling is completed, the contents of the primary memory 4 are transferred to the acquisition memory 7 through the primary data processing circuit 3a and the secondary data processing circuit 6a. At this time, the primary data processing circuit notifies the secondary data processing circuit of the presence of the glitch and its position information.

The secondary data processing circuit 6a reads glitch data from the memory 15 based on the notified information and transfers it to an appropriate area in the acquisition memory 7. The display processing circuit 8 uses the acquisition memory 7
Data is read out and the glitch data is inserted and displayed on the display screen of the display device 10 in the middle of the normal sampling points.

In the present invention, the presence of the glitch is thus detected in an analog manner, and only the peak value is inserted between the sampling points of the ADC and displayed. This makes it possible to easily detect and display glitches that were difficult to capture with conventional waveform measuring instruments.

The present invention is not limited to the above-described embodiments, and includes many changes and modifications without departing from the essence thereof.

For example, the detection target is not limited to the glitch, and the peak value of any waveform can be detected. That is, when the positive and negative two reference values other than the voltage zero point in the comparison circuit 12 are brought close to the zero point, the peak value of the waveform having a less steep peak can be captured.

As a result, it becomes possible to reproduce the waveform in a more accurate form on the display screen for all waveforms whose peaks are located between the sampling points.

Further, an oscilloscope usually has two or four channels, and a plurality of ADCs are always provided. Therefore, the low-speed ADC 14 can be configured to use the existing ADC without newly providing it. However, it is necessary to operate the glitch detection in a mode different from the normal sampling and disable the channel having the ADC used for reading the peak voltage.

Further, as for the memories, instead of mounting them individually, for example, an empty area may be provided in the primary memory 4 and the empty area may be allocated and used for another memory.

[0037]

As described above, according to the present invention, it is possible to easily detect a glitch existing between sampling points, which was difficult to be captured by the conventional waveform measuring instrument, and the sampling points are displayed on the display screen. The peak value of the glitch can be inserted and displayed in between to reproduce the input signal waveform more faithfully.

By adjusting the reference value for comparison in the comparison circuit, it is possible to easily detect and display the peak value of a waveform that is not as steep as a glitch.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an embodiment of a waveform measuring device according to the present invention.

FIG. 2 is a block diagram showing an example of a conventional waveform measuring device.

FIG. 3 is an example of a screen display when a glitch exists.

[Explanation of symbols]

1 input circuit 2 ADC 3a Primary data processing circuit 4 Primary memory 5 Trigger circuit 6a Secondary data processing circuit 7 Acquisition memory 8 Display processing circuit 9 Display memory 10 Output device 11 Differentiating circuit 12 Comparison circuit 13 Sample and hold circuit 14 low speed ADC 15 memory

Claims (4)

[Claims] 1. A waveform measuring instrument configured to sample a continuous input signal waveform at a predetermined interval, store the sampling data in an acquisition memory, and then read the sampling data and display it as a waveform on a display screen. A waveform characterized by detecting a glitch peak value by differentiating the input signal waveform and comparing it with a reference value, and inserting the peak value between the data of the sampling data for display. Measuring instrument. 2. A differentiating circuit for differentiating the input signal waveform,
The output signal of the differentiating circuit is provided with a comparing circuit that sets zero voltage and two positive and negative voltages as reference values and compares the output of the differentiating circuit with these reference values, and a sample hold circuit that samples and holds the input signal waveform. Detects the presence of a glitch when the signal passes the three reference values, and causes the sample hold circuit to hold the value of the input signal waveform when the output value of the differentiating circuit is zero as the peak value of the glitch. The waveform measuring instrument according to claim 1, which is characterized in that. 3. When the presence of the glitch is detected, the time relationship between the time when the glitch is detected and the sampling data is obtained, and the peak value of the glitch is set to the sampling data area of the acquisition memory corresponding to this time relationship. The waveform measuring instrument according to claim 1 or 2, further comprising processing means for transferring. 4. The waveform measuring instrument according to claim 1, wherein a low-speed analog-digital converter is used as an analog-digital converter for converting the data held in the sample-hold circuit into a digital signal.