To Select The Internal Trigger; To Select A Gated Trigger - HP 86140A Series User Manual

Using the Optical Spectrum Analyzer
The Bandwidth/Sweep Menus

To select the internal trigger

1 Press the front-panel Bandwidth/Sweep key.
2 Press the More BW/Sweep Functions.... softkey.
3 Press the Trigger Mode.... softkey.
4 Press the Internal softkey.
Internal triggering synchronizes the start of the sweep to an internally gener-
ated trigger signal. Internal triggering ensures continuously triggered sweeps
with the shortest delay between sweeps.

To select a gated trigger

1 Press the front-panel Bandwidth/Sweep key.
2 Press the More BW/Sweep Functions.... softkey.
3 Press the Trigger Mode.... softkey.
4 Press the Gated softkey.
In some measurements, the spectrum at a particular time within the modula-
tion period is more important than the average spectrum. Gated triggering can
be used to synchronize the data acquisition portion of the OSA to a gating trig-
ger connected to the rear-panel EXT TRIG IN connector. Gated triggering
requires a TTL-compatible signal with a minimum of 0 Vdc and a maximum of
+5 V.
Gated triggering is used to select data samples containing valid information.
When the gating signal is high, the data sample is accepted. When the gating
signal is low, the data sample is replaced by a data point with a value of
–200 dBm. The sweep time must be long enough to get data for each wave-
length point, or else the Max Hold function must be used to complete a trace
over several sweeps.
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