8–4
Triggers and When to Use Them
Trigger Source The trigger source may be:
Ø The acquisition channel signal (CH 1, CH 2 or CH 3, CH 4
on four-channel models) conditioned for the overall voltage
gain, coupling, and bandwidth.
Ø The line voltage that powers the oscilloscope (LINE). This
can be used to provide a stable display of signals
synchronous with the power line. Coupling and level are not
relevant for this selection.
Ø The signal applied to the EXT BNC connector (EXT). This
can be used to trigger the oscilloscope within a range of
± 0.5 V, or ± 5 V with EXT/10 as trigger source.
Level Level defines the source voltage at which the trigger circuit will
generate an event (a change in the input signal that satisfies the
trigger conditions). The selected trigger level is associated with
the chosen trigger source. Note that the trigger level is specified
in volts and is normally unchanged when the vertical gain or
offset is modified.
The Amplitude and Range of the trigger level are limited as
follows:
Ø ± 5 screen divisions with a channel as trigger source
Ø ± 0.5 V with EXT as trigger source
Ø ± 5 V with EXT/10 as trigger source
Ø None with LINE as trigger source (zero crossing is used).
Coupling This is the particular type of signal coupling at the input of the
trigger circuit. As with the trigger level, the coupling can be
independently selected for each source. Thus changing the
trigger source can change the coupling. The types of coupling
able to be selected are:
Note: Once specified, Trigger Level and Coupling are
the only parameters that pass unchanged from mode
to mode for each trigger source.
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