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82 L4400 User’s Guide
3 Operating and Programming
Figure 3-13. Scanning with External Instruments.
Figure 3- 14 shows the connections required to make a series (scan) of
two-wire measurements (e.g. ohms, DCV) using ABus1 of the L4421A .
Sequence The L4421A outputs a Channel Closed pulse on pin 5 of its Ext
Trig connector when a relay is closed and has fully settled (including any
channel delay). By connecting this pin to the DMM’s external trigger (Ext
Trig) input, the DMM is triggered to take a measurement. When the
measurement is complete, the DMM outputs a pulse from its DMM (VM
Complete) output. Connecting this output to pin 1 (Channel Advance) of the
L4421A’s Ext Trig connector advances the scan and closes the next channel
in the scan list.
Input
Channels
Common Terminals
(COM)
H
L
DMM