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TMP411: TMP411ADR Sensor Data Discripency

Gowtham M P
Prodigy 50 points
Part Number: TMP411
Other Parts Discussed in Thread: TMP119, TMP117, TMP461

Tool/software:

Hi TI Team,

We are using the TMP411ADR in our project to monitor the junction temperature (Tj) of a processor on our card. Based on the captured Tj data, we are back-calculating the case temperature (Tc). In parallel, we have connected a thermocouple directly to the case of the processor.

However, we are observing a discrepancy of approximately 2.3°C between the TMP411ADR's data and the thermocouple readings.

Could you kindly advise if there is a recommended correction or calibration factor that should be applied in this case to improve the accuracy of the temperature measurements?

Regards,

Gowtham M P

  • 0
    TI__Expert 7170 points

    Hi Gowtham,

    This level of error is plausible taking into consideration the sources of error from such a system:

    • TMP411 accuracy of +-1°C between 15°C to 75°C.
    • Thermocouple accuracy--which will depend on the type of thermocouple.
    • The thermal response of the system between the junction-case-thermocouple. Allowing enough time for the temperature to settle is recommended when testing with a temperature forcing element.
    • Accuracy of the ambient temperature setup. If using a temperature forcing unit or just ambient temperature, there can be fluctations in temperature which will cause a difference between the case temperature, the thermocouple, and the internal junction temperature of the processor.

    Implementing a calibration factor could be an option if you have a reference that has higher accuracy than the TMP411. Keep in mind that a calibration factor will vary between devices since the accuracy spec comes from process variation so an offset implemented would need to be unique to each device/module. I would recommend using a better reference for temperature sensing such as TMP117 or TMP119 (to replace the thermocouple).

    If higher accuracy is needed, I would recommend looking into a device with a better spec such as TMP461 for example.

    Best regards,

    Simon Rojas

  • 0
    TI__Expert 8730 points

    Hello Gowtham,

    There are two approaches you can take when calibrating the remote junction readings. TMP411 provides offset correction and n-factor correction. You will need to collect temperature of the processor and the thermocouple across temperature. 

    1) If your error is consistent across the full temperature range, you can enter the offset within the remote offset I2C register.

    2) If your error is not consistent across the full temperature range, the n-factor of the embedded junction within the processor is different than our designed n-factor of 1.008. This value can be changed within the I2C register. Calculations for N-factor is shown below

    Best Regards,

    Meredith McKean