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TMP006 Transient Correction

Sheng Luo
Intellectual 430 points

Other Parts Discussed in Thread: TMP006

Hi,

6 months ago, I started the project to use TMP006 to measure case temperature. I have done many experiments to find the best result. But I am sorry
the result is not same as I expected. I still struggle to find the root cause. Could you please clarify following questions as more as possible?
  1) What does standard 3D equation, which was stated in Transient Correction Algorithm created by Ian, mean?
  2) When TMP006 works in a stable enviroment and no object is placed in front of TMP006, the calculated result will rise from 10 degree to 17 degree in about 8 minutes.
       The increased amount seemed similar to self-heating. What is problem with TMP006 or calculating equations?
  3) Regarding S0 calibration, I have posted some questions in another thread. But I did not receive answers.
         http://e2e.ti.com/support/other_analog/temperature_sensors/f/243/p/241371/865352.aspx#865352
     Several days ago I used 7.0E-14 as S0 to run the test again, the calculated result was far smaller than physical temperature.
     What is the problem?

BRs,

Luo

  • 0
    TI__Mastermind 27715 points

    Hello Luo,

    I understand that this issue has been ongoing for quite some time and I do apologize.

    1) "Standard 3D equation" refers to the set of standard TMP006 equations given on p. 10 of the TMP006 User's Guide. Technically, it defines a 3-dimensional system which is why it's referred to as a 3D equation.

    2) The TMP006 consumes very little power and should not self-heat by any more than fractions of a degree when in a stable thermal environment. Are you using the TMP006EVM for this test or a board of your own design? Is there anything else on the board which could be dissipating a large amount of heat? How close is the TMP006 to the target object? It's possible that the TMP006 is being heated by the hot water.

    3) Here are the answers to your questions in the linked thread:

    1) In my spreadsheet, first row is physical temperature of water. 16 and 85 are minimum and maximum respectively. Tref is fixed to 298.15 K (25 degree) which is stated in TMP006 SBOU017. But in your spreadsheet,  Tref is set to 16 and 85 degree. Why? What does Tref mean?

    In my previous two-point calibration spreadsheet, TREF was the reference temperature measurement. In your experiment, this is the actual water temperature. However, in my generic TMP006 spreadsheet TREF is indeed 298.15 K. Sorry for the confusion. In my new two-point calibration spreadsheet I changed TREF to TOBJ to be more clear.

    2) In your spreadsheet, C2 is not taken into account. What is impact? I guess it can be ignored.

    We have found that C2 has an insignificant impact in the system behavior, so we've set it to zero.

    3) If I use 7.0E-14 as S0, the calculated result is far smaller than physical temperature. For example, in last column, the calculated result is 42 degree. But physical temperature of water is 86 degree. What is the problem?

    I found an error with my previous calibration spreadsheet, please see the attached file for the corrected version.

    4) Could you please point out what is wrong with my calculation? How to correct it?

    The issue with your calculation is that you calculate an S0 for each temperature point. The proper method is to calculate the overall S0 with the slope of the Cal. Function vs. (TOBJ4 - TDIE4). I've attached a new two-point calibration spreadsheet with some corrections that I'd like you to try. The result of this calibration is S0 = 2.26e-14. 

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog 

    TMP006 S0 Two-point Calibration_Luo_corrected.xls
  • 0 in reply to Ian Williams
    Intellectual 430 points

    Hi Ian,

    I am very appreciating for your fast clarification of most questions. Regarding question (2), Below is my comments.

    (2) Are you using the TMP006EVM for this test or a board of your own design? Is there anything else on the board which could be dissipating a large amount of heat? How close is the TMP006 to the target object? It's possible that the TMP006 is being heated by the hot water.

    The board was designed by myself. No hot water was placed near TMP006. I am sure that one LDO, one voltage reference and one MCU are close to TMP006. The distance is about 1-2cm. I guess the PCB layout does not follow TMP006 layout guidelines. This is one reason.
    I have used TMP006EVM to do same test. The result is same as you stated.  Regarding conducting heat, if you have any software workarounds to counteract it, please share with me. Thanks.

    BRs,

    Luo

  • 0 in reply to Sheng Luo
    TI__Mastermind 27715 points

    Hi Luo,

    You said that when you used the TMP006EVM, the result is the same as I stated. Can you clarify what this means?

    Following the recommended TMP006 PCB layout is critical to achieving accurate performance. The layout provides thermal isolation from surrounding circuitry and creates a balanced thermal environment that both protects against local temperature transients and allows for quick changes in object temperature.

    There is a software technique for reducing the effect of local temperature transients. The attached code contains this technique.

    Best regards,

    Ian Williams

    TMP006_Fixed_Point_Source_Code.zip
  • 0 in reply to Ian Williams
    Intellectual 430 points

    Hi Ian,

    Sorry, I have problem to login E2E these days. I mean the TMP006 consumes very little power and does not self-heat by any more than fractions of a degree.
    I have modified the PCB. Could you please help me double check if the attached does follow TMP006 SBOU108 or not? Thanks.

    BRs,
    Luo

  • 0 in reply to Sheng Luo
    TI__Mastermind 27715 points

    Hi Luo,

    I don't see an attachment in your post. Can you please re-upload it?

    Best regards,

    Ian Williams