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

Updated May 4, 2021

National Instruments does not actively maintain this document.

This content provides support for older products and technology, so you may notice outdated links or obsolete information about operating systems or other relevant products.

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?