Acquisition and Analysis of Abnormal Signals
1 Find out the abnormal signal
Step 1: observe the abnormality
How do I know if there is an abnormal signal?
Hearing is believing, seeing is believing. Zds2000 Series Oscilloscopes provide the simplest and effective way - infinite afterglow, which can keep the captured signal on the display. Coupled with the unique 330k "waveform refresh rate" of zds2000 Series Oscilloscopes, all abnormal signals have nowhere to escape under the condition of high waveform refresh rate.
Figure 1 shadow of abnormal signal
Generally speaking, the probability of abnormal signal is low, which is different from the normal signal. Therefore, the light gray waveform (low probability) in Figure 1 is likely to be the abnormal signal we are looking for. Unfortunately, although we see the abnormality, we can't view its details and make further analysis, because we still lack to save the abnormal data.
Step 2: condition capture
Through step 1, you can roughly understand the characteristics of the abnormal signal, regard its unique conditions as trigger conditions, and use the trigger to quickly capture the abnormal signal. Zds2000 Series Oscilloscopes are equipped with a variety of "trigger types" for free, including 11 basic triggers and 21 protocol triggers. In addition, users can also use "template trigger" according to the shape characteristics of the waveform to make the trigger more arbitrary.
Figure 2 using pulse width feature to trigger capture exception
Figure 3 using template touch to capture exceptions
Step 3: manual capture
Many times, there is no rule for exceptions. In the face of it, even the most powerful trigger will feel powerless. "Manual capture" can capture a large amount of data, save the data and put the abnormal signal into the bag. Specific methods:
Save all waveforms within a period of time. If there is any abnormality, it will be in the saved data. Zds2000 series oscilloscope is equipped with a maximum storage depth of 250mpt as standard, and can save data for 250s at a sampling rate of 1MHz.
Is it over when you catch an abnormal signal? No, that's just the basis for analysis. Next, we need to further understand the details and characteristics of abnormal signals, and finally analyze the causes of abnormal signals in essence, which is what we really need to do.
1. Measure
It is not enough to analyze the abnormal signal only through the visual performance of the waveform. Only by accurately quantifying the various indexes of the waveform can we see through the essence of the waveform abnormality. The 51 "true meaning" parameter measurements of zds2000 series oscilloscope standard configuration will statistically analyze all waveforms captured on the screen to obtain the current value, maximum value, minimum value, average value, standard deviation and statistical times of each item. Users can quickly understand the possible abnormalities in the waveform by observing the maximum and minimum values The standard deviation can quickly evaluate the signal characteristics.
Fig. 4 parameter measurement to find abnormal signal
2. Search
When debugging abnormal signals, we usually need to know the frequency of abnormal signals and whether they occur periodically? In order to find out these problems, it is generally necessary to record the waveform for a long time, and then locate and analyze the anomalies based on such a huge database. The standard "search function" of zds2000 series oscilloscope can quickly locate the signals of interest in a large amount of data and automatically make marks. Users can quickly understand the characteristics of abnormal location, frequency, cycle and so on by observing the marks.
Figure 5 search for abnormal large pulse
Figure 6 search for abnormal small pulse
Abnormalities are usually accompanied by interference signals. The 4m point "FFT operation" standard for zds2000 series oscilloscope is converted from time domain to frequency domain for analysis. At the sampling rate of 1GHz, the resolution of FFT can be accurate to 250Hz. Users can quickly and accurately analyze the abnormal signal and the source of abnormal signal by analyzing the power, RMS, phase and other characteristics of each frequency.
Zds2000 oscilloscope provides many powerful functions such as trigger, measurement, search and FFT, but the uncertainty of abnormal signal is very large. In practical application, it should be combined flexibly according to the specific situation, so as to improve the work efficiency to the greatest extent.
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