Trigger MODE (29) - Selects the mode of trigger operation as follows:
SINGLE (HOLD) - Selected using the lower button (29).
In this mode the 9400A digitizes until a valid trigger is
received. After the waveform has been acquired and displayed, no
further signals can be acquired until the SINGLE (HOLD) button has
been pressed again to re-arm the trigger circuit in preparation
for the next trigger signal. This type of acquisition provides a
simple means of recording a wide variety of transient events.
When the 9400A is in the Random Interleaved Sampling (RIS) mode,
sufficient number of triggers must be obtained to complete
waveform reconstruction, after which the waveform will be
displayed. No further signals can be acquired until the SINGLE
(HOLD) button has been pressed again.
When the 9400A is in the Roll mode (~ 500 msec/div), pressing the
SINGLE (HOLD) button causes data acquisition to immediately halt
and the display to freeze.
NORM - Selected using button (29).
When in the normal (NORM) trigger mode, the 9400A continuously
digitizes the input signal. Whenever a valid trigger is received,
the acquired waveform is displayed on the CRT, digitization starts
again and the trigger circuit is re-armed. If no subsequent
trigger is received within 2 seconds, previously acquired
waveforms are erased from the screen. The absence of a valid
trigger will thus result in a blank screen.
To retain the last acquired waveform indefinitely in the NORM
mode, the 9400A’s Auto-store feature is used. Auto-store can be
called via the Special Modes menu described in Section 5.2.5.
When the 9400A is in the RIS mode, a sufficient number (typically
200) of valid triggers is required for each display of a complete
waveform.
In the Roll mode (~ 500 msec/div), the 9400A samples the input
signals continuously. Each point is immediately updated on the
display. This results in a trace which moves from right to left
across the CRT. In the NORM mode, triggers are ignored. The only
way to halt data acquisition is to select the SINGLE (HOLD) mode
or switch the 9400A into AUTO mode and provide a trigger.
5-9
Manual Operation
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