Teledyne LeCroy WaveSurfer MXs-B Getting Started Manual - Manual (Page 34)

WaveSurfer MXs-B Oscilloscopes
26 922172-00 Rev A
RIS Sampling Mode - For Higher Sampling
Rates
RIS (Random Interleaved Sampling) is an acquisition technique that allows
effective sampling rates higher than the maximum single-shot sampling
rate. It is used on repetitive waveforms with a stable trigger. The maximum
effective RIS sampling rate is achieved by making multiple single-shot
acquisitions at maximum real-time sample rate. The bins thus acquired are
positioned approximately 20 ps (50 GS/s) apart. The process of acquiring
these bins and satisfying the time constraint is a random one. The relative
time between ADC sampling instants and the event trigger provides the
necessary variation.
The instrument requires multiple triggers to complete an acquisition. The
number depends on the sample rate: the higher the sample rate, the more
triggers are required. It then interleaves these segments (in the following
graphic) to provide a waveform covering a time interval that is a multiple of
the maximum single-shot sampling rate. However, the real-time interval
over which the instrument collects the waveform data is much longer, and
depends on the trigger rate and the amount of interleaving required.
Roll Mode
Roll mode displays, in real time, incoming points in single-shot acquisitions
that have a sufficiently low data rate. The oscilloscope rolls the incoming
data continuously across the screen until a trigger event is detected and
the acquisition is complete. The parameters or math functions connected
to each channel are updated every time the roll mode buffer is updated, as
if new data is available. This resets statistics on every step of Roll mode
that is valid because of new data.