Tektronix TDS5054, Руководство пользователя

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Triggering
TDS5000 Series User Manual
3- 51
compatible with most probes, nor can you display the auxiliary trigger
signal.
The oscilloscope provides the following trigger type categories:
H
Edge triggers are the simplest and most commonly used trigger type, used
with both analog and digital signals. An edge trigger event occurs when the
trigger source passes through a specified voltage level in the specified
direction (rising or falling signal voltage).
H
Pulse triggers are special-purpose triggers that are primarily used with digital
signals. The following types of pulse triggers are available: Glitch, Runt,
Window, Width, Transition, and Timeout. Pulse triggers are available on the
main trigger only.
H
Logic triggers are special-purpose triggers that are primarily used with
digital logic signals. Two of the types, Pattern and State, trigger the
oscilloscope based on the Boolean operator you select for the trigger sources.
A third type, Setup and Hold, triggers when data in one trigger source
changes state within the setup and hold times that you specify relative to a
clock in another trigger source. Logic triggers are available on the main
trigger only.
H
Video
triggers are used to trigger the oscilloscope on specified fields or lines
of a video signal. You can use one of several preset video signal formats or
set a custom format.
The trigger mode determines how the oscilloscope behaves in the absence of a
trigger event:
H
Normal
trigger mode enables the oscilloscope to acquire a waveform only
when it is triggered. If no trigger occurs, the oscilloscope does not acquire a
waveform, and the last waveform record acquired remains “frozen” on the
display. If no last waveform exists, no waveform is displayed (see Figure
3--20).
H
Auto trigger mode enables the oscilloscope to acquire a waveform even if a
trigger does not occur. Auto mode uses a timer that starts after a trigger event
occurs. If another trigger event is not detected before the time out, the
oscilloscope forces a trigger. The length of time it waits for a trigger event
depends on the time base setting.
Auto mode, when forcing triggers in the absence of valid triggering events, does
not synchronize the waveform on the display (see Figure 3--20). In other words,
successive acquisitions are not triggered at the same point on the waveform;
therefore, the waveform will appear to roll across the screen. If valid triggers
occur, the display will become stable.
Trigger Types
Trigger Modes