Larson Davis System 824, Reference Manual

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10-8 824 Reference Manual 11/8/00
off and the Autostore function turned on, the 824 will only
store Leq, Max, and Min spectra.
Triggering
Turns triggering on or off. There are four parts to triggering:
Arm, Trigger, End, and Then. Arm and Trigger work in
tandem to create a two step trigger to start an Autostore. End
and Then work together to determine when to stop measur-
ing.
Trigger Source
You can also set the trigger source
from the Trigger Status display by
moving the cursor to the desired
band, press the
c
check key and
select “Set Source” from the menu.
Allows the user to select a filter or flat overall level as a trig-
ger source.
Arm Settings Menu
Arm Mode
Elapsed time and qualifying times
are evaluated only when a new
ByTime sample is created. This
causes the minimum effective time
resolution to become the same as the
update interval. The 824 becomes armed when the following conditions are
met:
• Now - The 824 will arm immediately.
• L < - When the level is less than the “Arm Level” for the
“Arm Time”, then, the 824 will arm.
“L” indicates the level of the filter
specified by the Trigger Source set-
ting. • L = - When the level is equal to the “Arm Level”, +/-0.5
dB, for “Arm Time” then the 824 will arm.
• L > - When the level is greater than the “Arm Level” for
“Arm Time”, then, the 824 will arm.
• Input - The 824 arms when the logic input line changes
to “Arm Logic In” state.
• Time - The 824 arms after the “Arm Time” seconds in
the ready mode.
By default, the RT60-A and RT60-B
instruments have Autostore and
ByTime enabled.