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72 L4400 User’s Guide
3 Operating and Programming
Scan Trigger Source
Usage:
• L4421A 40- Channel Armature Multiplexer
• L4450A 64- Bit Digital I/O (digital input, counter channels only)
• L4452A Multifunction Module (digital input, totalizer channels only)
You can configure the event or action that controls the onset of each sweep
through the scan list (a sweep is one pass through the scan list):
• You can set the instrument’s internal timer to automatically scan at a
specific interval. You can also program a time delay between channels in
the scan list (see “Channel Delay" on page 77).
• You can start a scan when an external TTL trigger pulse is received.
• You can start a scan when an alarm event (L4450A, L4452A) is logged on
the channel being monitored.
Interval Scanning
In this configuration, you control the frequency of scan sweeps by selecting a
wait period from the start of one trigger to the start of the next trigger (called
the trigger- to- trigger interval). If the scan interval is less than the time
required to measure all channels in the scan list, the instrument will scan
continuously, as fast as possible (no error is generated).
Figure 3-10. Trigger-to-Trigger Interval.
• You can set the scan interval to any value between 0 seconds and 99:59:59
hours (359,999 seconds), with 1 ms resolution.
• Once you have initiated the scan, the instrument will continue scanning
until you stop it or until the trigger count is reached. See “Trigger
Count" on page 75 for more information.
t
Sweep 1
Trigger 1
Sweep 2
Sweep n
Trigger 2
. . .
Trigger Timer
(0 to 359,999 seconds)