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ADS122C04: detection of a short circuit between the leads of a thermocouple

Geon Kim
Expert 1070 points
Part Number: ADS122C04

Hello,

We are planning to apply the ADS122C04 for K-Type Thermocouple measurement.

At present our concern is on the detection of a short circuit or an insulation failure between the leads of a thermocouple.

The reason is that this can form an unwanted, inadvertent theomocouple junction called a virtual junction.

Please advise me how I can apply the ADS122C04 to detect a short circuit or an insulation failure between the leads of a thermocouple.

Otherwise please inform me some TI device or reference design for this function.

Thank you for your guidance.

With regards,

G. Kim

  • 0
    TI__Guru** 113765 points

    Hi Geon,

    There is now a basic guide available for thermocouple (TC) measurements that can be found at:

    http://www.ti.com/lit/an/sbaa274/sbaa274.pdf

    Unfortunately there is not a specific discussion for a shorted TC case.  As you have already surmised, the shorted TC case is difficult to detect.  I would suggest looking at the examples in the guide using burnout current sources (BCS).  The BCS work well for detecting open or degrading TCs, but they can also be used for detecting shorted TCs.  You would provide an external shorted condition to determine a baseline measurement with the BCS enabled.  Any input filtering would need to be a part of this measurement as you will not see an exact '0' measurement.  Your algorithm would need to compare the BCS reading with the shorted condition.  You would also need to determine if there is a trend.

    This method of short detection works well with a catastrophic condition, but can also work if there is not a long time interval between measurements and a trend can be established.  This method can be used with the ADS122C04 as well as any of the ADCs having a BCS.

    Best regards,

    Bob B