1
Getting
Started
Functional Description
1-11
Run Modes
The 5251 can be programmed to operate in one of four run modes:
continuous, triggered, gated and (counted) burst. These modes are
described below.
Continuous Mode
In normal continuous mode, the selected waveform is generated
continuously at the selected frequency, amplitude and offset.
Triggered Mode
In triggered mode, the 5251 circuits are armed to generate one
output waveform. The trigger circuit is sensitive to transitions at the
trigger input. Select between positive or negative transitions to
trigger the instrument. When triggered, the generator outputs one
waveform cycle and remains idle at an amplitude level equal to the
voltage of the first point of the waveform. The instrument can be
armed to receive triggers from the front panel connector or using a
trigger soft command. The re-trigger mode require only one trigger
signal, which automatically generate a series of triggers spaced by
an interval that is determined by the re-trigger delay parameter.
The trigger signal, whether it comes from the front panel or from a
soft command, has to pass through some electrical circuits. These
circuits cause small delay known as system delay. System delay
cannot be eliminated completely and must be considered when
applying a trigger signal. It defines how long it will take from a valid
trigger edge to the moment that the output reacts.
Gated Mode
In gated mode, the 5251 circuits are armed to generate output
waveforms as long as a gating signal is present. Unlike the
triggered mode, the gated mode is level sensitive. When the gating
signal goes low, the waveform at the output connector is first
completed and the output reverts to an idle state. The idle
amplitude level, after the gating signal goes low, is the last point on
the waveform.
Burst Mode
The burst mode is an extension of the triggered mode where the
generator can be programmed to output a pre-determined number
of waveforms. The sources to trigger a burst are the same as for
the trigger mode.
Summary of Contents for 5251
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