National Instruments 321906B-01 ユーザーズマニュアル

Chapter 2

NI 2501/2503 Operation

2-8

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 National Instruments Corporation

When you use the NI 2501/2503 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 NI 2501/2503 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.

You can use multiple NI 2501/2503 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.