Operation
Use Auto for monitoring logic signals. Set the LEVEL control to the mean threshold
of the logic system, +1.4 V for TTL. The sweep then triggers on valid transitions and
free-runs to show static highs and lows.
Normal mode produces a sweep only when the trigger signal meets the Level and
Slope criteria.
Use Normal mode for infrequent events and erratic signals.
Sgl Seq mode accepts one trigger for each sweep in the display. Press the lower
Mode button to arm the trigger and illuminate the READY indicator for each sequence.
With a multi-trace display, a sequence comprises up to sixteen sweeps.
Use Sgl Seq to detect a rare event or to eliminate all but the first one of a chaotic
burst of pulses. Set the trigger for the signal of interest in Normal mode. Then press
the lower Mode button to select Sgl Seq and illuminate the READY indicator. To
detect the occurrence of a rare event, display a single trace and arm Sgl Seq with the
trigger set for the event. Periodically check to see if READY is on. If a burst of trigger
events occurs, the sweep runs once for each trace displayed and READY
extinguishes.
Trigger Source
Choose a single trigger source to correctly display the timing relationships
among multiple channels. Choose the channel with the lowest-frequency signal
to avoid ambiguous displays.
With Vert trigger source. Auto Lvl trigger mode or Chop vertical mode
automatically selects a single trigger source, the first one of the displayed
channels.
Use a composite A-Trigger source to compare asynchronous signals. To
generate a composite trigger, select Vert trigger source, a trigger mode other
than Auto Lvl, and Alt vertical mode.
Trigger Coupling
For noisy signals or signals with strongly interfering components, Noise
Reject, HF Reject, and LF Reject coupling give added selectivity. AC coupling
continues triggering when the dc level of the signal changes.
2465B/2455B/2445B Operators
2-7
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