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TMP006 die-obj temperature and accuracy

Vasile Surducan
Prodigy 60 points
Other Parts Discussed in Thread: TMP007, TMP006

Hello,

According to SBOU142 (TMP007 calibration guide) which math algorithm is applied to TMP006 as well, at page 24 is stated: "As with all thermopiles, as the difference in temperature between the object and the sensor increases, so will the error."

Can someone from the TI engineering team to explain the statement above?

At the first glance this seems not correct. For the same ADC resolution used in the TMP006, a higher difference between the object and die temperature will increase the voltage read by the ADC. My measurements indicate around 5x-15x increase in the voltage for 16 different TMP006 thermopiles. Assuming the sensor noise is not affected by the Tobj-Tdie value, as higher the voltage value, as lower the error will be.

thank you,

  • TI__Mastermind 27590 points

    Hi Vasile,

     

    Although not explicitly stated, the quote is most likely referring to second order effects, rather than from a pure error analysis angle.

     

    In calibration equation (4), Vos is basically the “cold” junction compensation. It is directly added to (or subtracted from) Vsensor. Vos is calculated assuming constant Tdie. In reality, heat transfer mechanisms other than IR radiation will cause Tdie to drift, and the drift will be bigger as the difference between Tdie and Tobj increases. This effect will cause increased error. The transient correction calibration can mitigate this effect to some degree.

     

    Regards,

    Guang-Apps Sensing Products

  • in reply to Guang Zhou
    Prodigy 60 points
    Hi Guang,
    Thank you for the answer but I still need your help.
    I'm trying to improve the TMP006 response and I think I've almost did it. :)

    I have 16 TMP006 which are seeing a gray body. In my application Tdie is kept constant with high accuracy.
    The problem is I'm not able to get identical readings (with reasonable errors) from the sensors just with S0 calibration.
    As far I've understood from TMP007 calibration (sbou142) a1 and a2 are die constants, but b0, b1 and b2 are variable.
    Where can I found an example describing using a dataset how the calibration should be done?
    The TMP007 calibration has no real example, which is not fair for a calibration instruction.

    thx,
    Vasile
  • in reply to Vasile Surducan
    TI__Mastermind 27590 points

    Hi Vasile,

     

    I understand your frustration. And I’m sorry I don’t have a ready example data set that I can send to you.

     

    However our in-house expert is working on an app aiming to make the calibration as painless as possible, with some limitations. We hope to have it available on a trial basis in a short time.

     

    Regards

    Guang-Apps Sensing Products

  • in reply to Guang Zhou
    Prodigy 200 points

    I'd be very interested in the calibration app when it's ready.
    --Eric