Other than the previously presented ETS method, Random Equivalent Time Sampling (RETS) continuously takes samples of the input signal.
The timings of the taken samples are not related to the trigger events. This leads to random taken samples of the signal in relation to the trigger events . The sampling timings of this ETS mode are derived from an internal clock. This process is illustrated in figure 1.
The signal displayed as a dotted line in figure 1, shows the reconstructed version of the input signal. Each dot represents a captured sample. The signal at the bottom of figure 1 represents the pulses generated by the trigger system. The illustration shows that during RETS, the taken samples are not in relation to the trigger pulses. For reconstructing the waveform of the input signal, the time interval between capturing a sample and detecting a trigger event is important. The trigger event before and after capturing the sample is used to reconstruct the time dependency of the input signal. This will restore the temporal connection between the randomly taken samples and the time characteristics of the input signal. The taken samples are combined together to correctly display the captured waveform. This ETS method enables pre-trigger waveform capturing which is not possible by SETS.