National Instruments NI 9214, Operating Instructions And Specifications, Page: 17 / 44

© National Instruments Corp. 17 NI 9214 Operating Instructions and Specifications
Cold-Junction Temperature Measurement Accuracy
The NI TB-9214 has three cold-j u nction compensation channels.
Heat dissipated by adjacent mod u les or other nearby heat so u rces
can ca u se errors in thermoco u ple meas u rements by heating u p the
NI 9214 terminals to a different temperat u re than the cold-j u nction
compensation sensor. The thermal gradient across the terminals
can ca
u se the terminals of different channels to be at different
temperat u res, in which case the res u lting meas u rement creates
errors not only in absol u te acc u racy b u t also in the relative
acc u racy between channels. Refer to the Specifications section for
the cold-j u nction compensation acc u racy specifications. The
thermoco u ple acc u racy specifications incl u de the errors ca u sed
by the thermal gradient across the NI 9214 terminals for
config
u rations with the NI 9214 terminals facing forward or
u pward. Refer to the Temperature Measurement Accuracy section
in the Specifications section for the thermoco u ple acc u racy
specifications.
Minimizing Thermal Gradients
Thermal gradients can be ca u sed by changes in the ambient air
temperat u re near the front connector or by the thermoco u ple wire
if it cond u cts heat or cold directly to the terminal j u nctions. For the
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