What is CJC? Hardware: Signal Conditioning Other
Problem: What is CJC and why is it important? Solution: Thermocouples operate on the principle that dissimilar metals generate a voltage when in contact with one another. There are several common types of thermocouples (K, E, J, etc.), which are comprised of specific metal pairings. Each combination of metal yields a known voltage related to the temperature of the junction that can be characterized mathematically. In a measurement system, simply connecting a thermocouple to a data acquisition board or breakout box will add more dissimilar metal junctions, called cold junctions, to your circuit that may skew your measurement. Cold Junction Compensation (CJC) removes the effect of the voltages generated by these cold junctions for a more accurate temperature measurement. Some data acquisition boards and signal conditioning units have a built-in CJC terminal, which is a temperature reference on the board used to calculate and remove the unwanted voltages. Related Links: Developer Zone Tutorial: Taking Thermocouple Temperature Measurements KnowledgeBase 2FBGSAQO: How to Determine the Thermocouple Type and the Correct Polarity of Signal Connections KnowledgeBase 0Z63B4AQ: How Can I Address and Use Cold Junction Compensation (CJC) with SCXI Modules? Attachments:
Report Date: 11/03/2005 Last Updated: 04/07/2008 Document ID: 3R27J3GH |
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