Inconsistent Open Thermocouple Channel Readings in Scan Engine Mode

Updated Dec 5, 2017

Reported In

Hardware

  • NI-9214
  • cRIO-9037

Software

  • LabVIEW Full

Driver

  • NI-RIO
  • NI CompactRIO

Other

C Series modules that have Open Thermocouple Detection (OTD)

Issue Details

I have a module that has the Open Thermocouple Detection function. When measuring channels with an open thermocouple connection, depending on which method I'm using, I get different values. What is the reason for this?

Solution

This is an expected behavior due to different front-end scan interface reading methods. The values returned can be either 0 or full scale positive reading of the selected thermocouple type.

It is not recommended to use this value as a means to detect an open thermocouple connection. As 'Error -65582: An open thermocouple was detected' is always returned regardless of which method is used, it is recommended that you handle this error as a means of detecting an open thermocouple instead.

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