The influence of dead zone time and waveform capture rate on measurement results of oscilloscope
Many engineers may encounter in the process of hardware debugging would have been to such a situation: in the late stages of debugging, presented in the paper.the main parts of the circuit board welding was basically completed, in the functional verification process, soon found a running system will be out of order, but through the oscilloscope to see key clocks and enabling signal "no problem", will ultimately be the cause of the problem as in the software, and then check the code line by line, software optimization.Now we have a clear understanding of the dead zone time of the oscilloscope. For the above situation, there is another possibility that the oscilloscope missed the occasional signal that caused the system failure
Due to the existence of dead zone time of oscilloscope, it may miss key abnormal signals and display a deceptive result to the user, thus misleading the user's judgment, which will greatly prolong the debugging time and reduce the debugging efficiency.
Suppose a signal carries an exception that repeats 10 times per second.The signal itself is displayed on the oscilloscope in the form of data, and the horizontal scale adopted is 10ns/div.If the display used has 10 horizontal bars, the effective capture time of 100ns can be calculated.To ensure a high degree of confidence in capturing the desired signal events, a 99.9% probability is required.Now, the required test time depends on the waveform capture rate of the oscilloscope.The following table statistics several different waveform capture rate of the required test time.
Although the dead zone time ratio of RTO series oscilloscopes of R&S is close to 90% under this condition, compared with other oscilloscopes with the dead zone time ratio of 99.5% or more, its ability to find occasional abnormal signals is an order of magnitude increase, which can help engineers greatly improve debugging efficiency.How many engineers can look at each signal on an oscilloscope for more than seven seconds?
Also mentioned, in front of the waveform capture rate and the horizontal scale set, record length, sampling rate, there is relationship, in actual measurement, according to the actual measured signal, is to find a balance point in the parameter Settings to see the highest acquisition probability wave, improve the efficiency of debugging, this is an engineer in the digital oscilloscope in use process need to consider the question.