Greetings,
The following KnowledgeBase explains the concept of open-thermocouple detection:
Open-Thermocouple DetectionSince the SCXI-1120/SCXI-1320 combination does not have open-thermocouple detection circuitry, you will need to provide it yourself by connecting pull-up resistors between the CH+ terminals and voltage references. Since the channels of the SCXI-1120 are isolated, it is important to realize that connecting multiple pull-up resistors to the same voltage reference will break this isolation.
Good luck with your application.
Spencer S.