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Using the Oscilloscope
The Scope Trigger Menu
Auto-Trig field
The Auto-Trig field allows you to specify whether or not the
acquisitions should wait for the specified trigger condition to occur.
When you select the Auto-Trig field, the field toggles between On and
Off. The On and Off fields are discussed below.
The default selection for the Auto-Trig field is On.

On

When you set auto-trigger to On, the oscilloscope waits 50 ms (20-Hz
rate) for a trigger to occur. If a trigger does not occur within that time,
the current contents of acquisition memory are displayed. The
message "Auto triggered" is displayed if one of the following conditions
occurs:
•No signal is on the input. In this case, the oscilloscope will display a
baseline.
•There is a signal but the specified trigger condition has not been met
within 50 ms. In this case, the waveform display will not be synchronized
to a trigger point.
Off
When you set auto-trigger to Off, the oscilloscope waits until a trigger
is received before the waveform display is updated. If a trigger does not
occur, the screen is not updated and the message "Waiting for Trigger"
is displayed. Use this mode when:
•The trigger source signal has less than a 20-Hz repetition rate.
•The trigger events counter (refer to "Count field") is set so that the
number of trigger events would not occur before 50 ms.
•When you want to trigger on a specific event only.