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TMP006B Big temperature error

Anton Ruban
Prodigy 50 points
Other Parts Discussed in Thread: TMP007, TMP006

Hello,

I am using TMP006B in my project on custom PCB

The measured temperature has huge offset of about +90 C°

I tried to  adjust the calibration coefficients, but the only change the result by +-10 C°

Interestingly, if I set the Number of Averaged Samples (through control registers) to 1, the error is huge, like 800°C

The more samples i average, the close is my result to the real world. As if first  one or two conversions are completely false.

The voltage to TMP is stable, although i dont have oscilloscope to measure it  precisely.

Here is my layout  footprint and schematics :

  • 0
    TI__Mastermind 31590 points
    Hi Anton,

    Let's me review and get back to you.

    Aaron
  • 0 in reply to Aaron Heng
    Prodigy 50 points

    I just replaced the TMP to new one.
    Now it works backwards. If I hold something hot over the sensor , it shows negative temperature, while holding nothing shows positive temperature. That is rly strange since I used exact same code on my dev. board.

    If I heat up the PCb, the Die Temperature increases and shows the right value.

    SO the Vobj is wrong, or i have to calculate completely diffferent coefficients for my calculations....

  • 0 in reply to Anton Ruban
    TI__Intellectual 1811 points

    Anton,

        Thanks for you post and sorry for the delay.  I looked at the footprint you attached and it all looks reasonable. From what I gather you are using the default settings.  Keep in mind that the default settings assume that the object is 100% of the field of view.  With TMP006 and TMP007 having nearly a 180°FOV you need to be very close if you have no FOV restriction.  So having said that.  We have an EVM TMP007EasyCalEVM.  It has software that you can download.  It is designed to Work with the EVM hardware, but it has an Analysis page that allows you to upload data from an external .csv file.  If you take some data and upload it,   the software will help you calculate the right coefficients for your setup.  If you would like to upload pictures of you set up, i can get a better idea of any problems you may be having.  Also the only time I have seen such large errors is when trying to measure an object with very low emissivity,  like a shiny metal surface.  TMP006/007 can only measure temperature of surfaces with high emissivity .8 or .9 is best.  If this is the case you can  try painting the surface with Flat black spray paint.  Let me know if any of the helps.  I'm glad to help you figure this out.

    Regards,

    Tommy Santoyo

    MHRS Sensing Apps Team

  • 0 in reply to Tommy Santoyo
    Prodigy 50 points
    Ok. I solved the problem. I turned out to be dirt (flux residue) under the chip, which made contact between the chip and pcb.
    So what I did is heat the whole board to 120-130 C° and then let some isopropanol flow under the TMP006 (I used syringe to keep small steady stream of IPO though the chip.)
    After 5 minutes i let the system to cool down, and now it works just fine.
    Thank you for taking time to help me.