Wrong Data from Built-In CJC Sensor on C Series Modules

Updated Jan 16, 2018

Reported In

Hardware

  • NI-9210
  • NI-9211
  • NI-9213
  • NI-9214

Issue Details

I am using DAQmx Create Virtual Channel to acquire data both from my CJC sensors (AI Temp-Built-In Sensor) and analog input channels (AI Temp TC). The data coming in is incorrect. Why is this happening and how can I fix it?

Solution

There exists a known issue with DAQmx documented in CAR 616702 and has been resolved in NI-DAQmx version 17.1 and newer. Data corruption may occur when two DAQmx Create Virtual Channel VIs are used in the following order:
  1. DAQmx Create Virtual Channel AI Temp Built-In Sensor
  2. DAQmx Create Virtual Channel AI Temp TC

This issue is seen with the following C series modules:
  • NI 9210
  • NI 9211
  • NI 9213
  • NI 9214

Additional Information

The recommended way to read an internal CJC sensor simultaneously with an AI Temp TC operation is described in KnowledgeBase How Can I Read Data from the Built-In CJC Sensor on My DAQ Device in LabVIEW?

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