Teledyne Lecroy WaveSurfer 3000, Operator'S Manual, Page: 37 / 97

Operator's Manual
Sampling Modes
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, the
waveform is horizontally positioned so that the trigger event is time zero 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
In Real Time sampling mode, the acquisition can be displayed for a specific period of time (or number of samples) either
before or after the trigger event occurs, known as trigger delay. This allows you to isolate and display a time/event of
interest that occurs before or after the trigger event.
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Pre-trigger delay displays the time prior to the trigger event. This can be set from a time well before the trigger
event to the moment the event occurs, up to the oscilloscope's maximum sample record length. How much
actual time this represents depends on your timebase setting. When set to the maximum allowed pre-trigger
delay, the trigger position (and zero point) is off the grid (indicated by the trigger delay arrow at the lower right
corner), and everything you see represents pre-trigger time.
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Post-trigger delay displays time following the trigger event. Post-trigger delay can cover a much greater lapse of
time than pre-trigger delay, up to the equivalent of 10,000 time divisions after the trigger event occurred. When
set to the maximum allowed post-trigger delay, the trigger point may actually be off the grid far to the left of the
time displayed.
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.
Sequence Sampling Mode
In Sequence Mode, the complete waveform consists of a number of fixed-size segments (see the instrument
specifications at teledynelecroy.com for the limits). The oscilloscope uses the sequence timebase setting to determine
the capture duration of each segment as 10 x time/div. With this setting, the oscilloscope uses the desired number of
segments, maximum segment length, and total available memory to determine the actual number of samples or
segments, and time or points.
Sequence Mode is ideal when capturing many fast pulses in quick succession or when capturing few events separated
by long time periods. The instrument can capture complicated sequences of events over large time intervals in fine
detail, while ignoring the uninteresting periods between the events. You can also make time measurements between
events on selected segments using the full precision of the acquisition timebase.
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