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ADS122C04: thermocouple sense

Part Number: ADS122C04
Other Parts Discussed in Thread: TMP75, LM94022

Hi Expert,

Since customer need to connect the converter to thermocouples to sense temperature, we have to confirm if ADS122C04 can replace to MCP3422.

some of questions need you help to check as below:

  1. If they use all 4 channels for 2 thermocouples, how do they apply the cold junction compensation? Can it be done by using a TMP75’s temp reading?
  2. Is there any specific reason that customer has to LM94022 for the CJC instead of other sensor like TMP75?
  3. As datasheet use LM94022 & ADS122C04, how do we make sure the cold junction compensation works? Currently my concern is at the red mark in isothermal block, I want to confirm how we implement this routing for cold bath for the thermocouple which measures the hot point.



  • Hi Mark,

    If you connect 2 thermocouples to the ADS122C04, then there is no way to connect an analog output temperature sensor for measurement by the ADC without using an external mux.  Some customers are able to place the ADS122C04 within the cold-junction area and use the internal temperature sensor of the ADS122C04.

    There are actually many methods that can be used for the cold-junction measurement.  Devices such as the TMP75 are possibilities, but which method is chosen depends on the desired measurement accuracy and overall cost.  A digital temperature sensor makes a lot of sense for this application so I would suggest doing a parametric search for the best option:

    The customer may find the information helpful in A Basic Guide to Thermocouple Measurements which also contains some of the other cold-junction measurement solutions.

    Best regards,

    Bob B