Chapter 2 NI2501/2503 Operation
NI 2501/2503 User Manual 2-8
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National Instruments Corporation
Initiating Scanning
When you use the NI 25 01/2503 to initiate a scan, make sure the
measurement device is armed (waiting for trigger) before enabling
scanning on the switch card. Enabling scanning causes the first switch(es)
in the scan list to close and generates a scanner advanced trigger after the
relay/FET switches have settled or debounced.
When you use the measurement device to initiate a scan, make sure
scanning is enabled on the NI 2501/2503 before the measurement device
starts to take measurements. This ensures that the switch card has the
correct signal routed and that the switch card is waiting for an external
trigger from the measurement device.
Always configure the triggers in a system before configuring the
measurement device or the NI2501/2503 for scanning. When triggers are
configured, a state change or pulse could occur on the trigger line. This is
also possible when you reset the switch card.
Multicard Triggering
You can use multiple NI2 501/250 3 switch cards together in conjunction
with an instrument such as a DMM. In multiple switch-card systems,
be sure to identify one switch card as the master switch card.
All other switch cards for the system are identified as slave switch cards.
The master switch card can route an external trigger from the front
connector to a PXI backplane trigger. In addition, the master switch card
can route the SCANADV trigger from the PXI backplane to the front
connector. This functionality makes it possible to wire external triggers
from/to only one switch card in the system, which simplifies the wiring
scheme.
For more information, refer to the NI-SWITCH Software User Manual.