Trigger Key points
1. Trigger Source:
Trigger can occur from several sources: Input channels (CH1 and CH2), AC Line,
Ext, Ext/5.
CH1 or CH2:
It is the most commonly used trigger source. The channel works when selected
as a trigger source whatever displayed or not.
Ext Trig:
The instrument can be trigger from a third source while acquiring data from CH1
and CH2. For example, to trigger from an external clock or with a signal from
another part of the test circuit. The Ext, Ext/ 5 trigger sources use an external
trigger signal connected to the EXT TRIG connector. Ext uses the signal directly; it
has a trigger level range of +1.6 V to -1.6 V. The EXT/ 5 trigger source attenuates
the signal by 5X, which extends the trigger level range to +8 V to -8 V allowing
the oscilloscope to trigger on a larger signal.
AC Line:
AC power can be used to display signals related to the power line frequency, such
as lighting equipment and power supply devices. The oscilloscope gets triggered
on its AC power input, an AC trigger signal is not required. When AC Line is
selected as trigger source, the oscilloscope automatically set coupling to DC, set
trigger level to 0V.
2. Sweep Mode:
The sweep mode determines how the oscilloscope behaves in the absence of a
trigger event. The oscilloscope provides three trigger modes: Auto, Normal, and
Single.
Auto:
This sweep mode allows the oscilloscope to acquire waveforms even when it does
not detect a trigger condition. If no trigger condition occurs while the oscilloscope
is waiting for a specific period (as determined by the time-base setting), it will
force itself to trigger.
When forcing invalid triggers, the oscilloscope cannot synchronize the waveform,
and the waveform seems to roll across the display. If valid triggers occur, the
display becomes stable on the screen.
Any factor results in the un-stability of waveforms can be detected by Auto
Trigger, such as the output of Power supply.
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