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Note An active reference clock (oscillator) is required for the digitizer to
recognize and accept arm signals.
Setting the Trigger
Count
The trigger count is the total number of readings (pre- and post-arm) per
arm event. The trigger count is normally set by the <size > parameter of the
CONFigure and MEASure commands. However, when you want to change
the total reading count without entirely re-configuring the digitizer, the
reading count (trigger count) can be set with either of the following
commands:
TRIGger[:STARt]:COUNt <
count
>
SENSe[<
chan
>]:SWEep:POINts <
count
>
Setting the Pre-Arm
Reading Count
Pre-arm readings are samples the digitizer takes before an arm signal is
accepted. Pre-arm readings start after the digitizer receives the
INITiate[:IMMediate] command. Readings continue until the pre-arm
reading count is reached, and until the arm is received. The command which
sets the minimum number of pre-arm readings is:
SENSe[<chan >]:SWEep:OFFSet:POINts <count >
<count > is specified as a negative number. You must specify at least three
pre-arm readings and seven post-arm readings. Refer to the SENSe
subsystem in Chapter 4 - "Command Reference" for more details on setting
the pre-arm reading count.
If the pre-arm reading count is reached and the arm has not occurred, the
readings continue and overwrite previous readings. When the arm occurs,
the most recent number of <count> readings are stored in memory. If an
arm occurs before the pre-arm reading count is reached, the arm is ignored
and error -212 "Arm ignored" is generated.
Sending an Immediate
Trigger
In some applications the user may want to manually issue a sample trigger.
This is accomplished with the command:
TRIGger[:STARt][:IMMediate]
When the digitizer is armed (wait-for-trigger state), executing
TRIG:STAR:IMM takes a reading regardless of the specified trigger source.
The trigger count is decremented by 1 and the selected trigger source
remains unchanged. TRIG:STAR:IMM is often used with
TRIG:SOUR:HOLD to suspend triggering until the trigger is issued by
TRIG:STAR:IMM.
Chapter 3 Understandin
g
the HP E1429 Di
g
itizer 125