Sampling Mode - Teledyne HDO9000 Operator's Manual

Sampling Mode

The Sampling Mode setting determines how the instrument samples the input signal and renders it
for display.
Real Time Sampling Mode
Real Time sampling mode is a series of digitized voltage values sampled on the input signal at a
uniform rate. These samples are displayed as a series of measured data values associated with a
single trigger event. By default (with no Delay), the waveform is positioned so that the trigger event is
time 0 on the grid.
The relationship between sample rate, memory, and time can be expressed as:
Capture Interval = 1/Sample Rate X Memory
Capture Interval/10 = Time Per Division
Usually, on fast timebase settings, the maximum sample rate is used when in Real Time mode. For
slower timebase settings, the sample rate is decreased so that the maximum number of data
samples is maintained over time.
Roll Sampling Mode
Roll mode displays, in real time, incoming points in single-shot acquisitions that appear to "roll"
continuously across the screen from right to left until a trigger event is detected and the acquisition
is complete. The parameters or math functions set on each channel are updated every time the roll
mode buffer is updated as new data becomes available. This resets statistics on every step of Roll
mode that is valid because of new data.
Timebase must be set to 100 ms/div or slower to enable Roll mode selection. Roll mode samples at
≤ 5 MS/s. Only Edge trigger is supported.
Note: Roll sampling is not available when in HD Mode. If the processing time is greater than
the acquire time, the data in memory is overwritten. In this case, the instrument issues the
warning, "Channel data is not continuous in ROLL mode!!!" and rolling starts again.
RIS Sampling Mode
RIS (Random Interleaved Sampling) allows effective sampling rates higher than the maximum single-
shot sampling rate. It is available on timebases ≤ 10 ns/div.
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 5 ps (200
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.
Because the instrument requires multiple triggers to complete an acquisition, RIS is best used on
repetitive waveforms with a stable trigger. The number depends on the sample rate: the higher the
sample rate, the more triggers are required. It then interleaves these segments (as shown in the
following illustration) to provide a waveform covering a time interval that is a multiple of the
Acquisition
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