Reference
Bottom Side Description
Auto (untriggered
roll)
Enables free-running and roll-mode
acquisitions.
Normal Tr iggers only on valid trigger events.
Holdoff (time) Sets holdoff to a specifictime.
Holdoff (% of
record)
Sets holdoff to a percent of the record
duration.
Mode &
Holdoff
Set to Min Sets holdoff to the minimum value.
Key Points
Displaying the Trigger Source. You do not have to display a channel to use it as
a trigger source.
NormalandAutoMode. Use Normal trigger mode when you want to trigger
only on a valid event. Use A uto trigger mode when you want the acquisition to
occur, even when there is not a valid trigger event. Also choose Auto when you
want a rolling waveform, with no trigger, at the slower time base settings. (See
page 71, Roll Mode Display.)
External Trigger. The trigger level range for the EXT setting is -0.8 V to +0.8 V.
The trigger level range for the EXT/10 setting is -8 V to +8 V.
For best external trigger performance, apply a square-wave signal with amplitude
greater than the specified minimum level range and with well-defined transitions.
Alternating Trigger. Alternating trigger sequentially uses each active channel as a
trigger source, from the lowest-numbered active channel to the highest-numbered
active channel. Alternating trigger is available in all trigger menus except for
logic triggers.
Alternating trigger uses the current trigger settings to trigger on all active
channels; there is not a separate trigger setup for each channel. Therefore, the
trigger settings must be able to trigger on all active signals in order to produce
a stable triggered display. If one or more of the source signals do not meet the
trigger settings, the oscilloscope either waits for that source channel to trigger
(Normal trigger mode) or autotriggers (Auto trigger mode).
Due to image persistence, all alternating trigger active channels may appear to
be synchronized. However, this d oes not mean that the displayed signals are
synchronized. Also, alternating trigger does not use EXT, EXT/10, or Line signals
as trigger sources.
Holdoff. You can use holdoff to help stabilize the display of complex waveforms.
After you push the Mode & Holdoff screen button, use the general purpose knob
to set the hold
off time as an absolute value or as a percent of the record duration.
Holdoff begins when the oscilloscope recognizes a trigger event and disables the
trigger system until acquisition is complete. The trigger system remains disabled
during the holdoff time.
96 TDS3000C Series Oscilloscope User Manual
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