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TMP006-How to Calculating the Target Object Temperatures

Jeff liu
Prodigy 115 points
Other Parts Discussed in Thread: TMP006, TMP007

Hello,

I am using TMP006 to measure a target object,I want to ask that if the object being measured not encompass the full FOV, the sensor will include the background temperature behind the target object in the measurement,and the temperature of object which measured may be mistake,so is there any equations or ways to calculate the  currect temperature?

BRs

Jeff Liu

  • 0
    TI__Expert 3370 points

    Hello Jeff,

    Yes, the sensor will detect IR radiation from the background as well as from the object. For this reason, it is recommend that the object cover the majority of the field of view, 110  degrees or greater ( see TMP007 product data sheet, SBOS685,  for definition of the Field of View). The TMP007 (or any other monopixel device) cannot distinguish between IR radiation form the object or from the background, it only senses the total energy.

     if the background temperature is constant then calibration will still be possible folowing the procedures outlined in the guide. The constant background temperature will show as an offset.  If the background temperature varies, then the reported object temperature will be a weighted average of the object and background. In this case it may be necessary to restrict the Field of View using an aperture (window with a hole in it).

    The equations used to calculate the temperature are given in TMP006 User Guide (SBOU107) section 5 and 6,

    Regards,

     

    Werner

  • 0 in reply to Werner Metz
    Prodigy 115 points

    Hello, Werner

       Thank you for you help.

      Another question is that if I use an aperture, but the device is put near a hot source ,the ambient temperature  is varies, it may be equal to the background temperature varies, can I also use the equations and calibration methods in TMP006?  If it is right which type of material of the shell (which to restrict the Field of the view ) may I use,a good emissivity material~1,or a bad one~0 ? 

    BRs

    Jeff Liu

  • 0 in reply to Jeff liu
    TI__Expert 3370 points

    Hi Jeff,

    The emissivity of the shell is less important than the thermal conductivity. Here is why -

    If the shell has high thermal conductivity and it is thermally grounded to the TMP007 die then the shell and TMP007 die will be at the same temperature. This means that they will radiate equally to each other and so the net IR energy transfer aproaches zero.as they reach thermal equilibrium. (the radiation emitted by the shell will equal the radiation emitted by the TMP007). This means a high thermal conductivity shell works best, which typically means a metal. Thermal conductivity is measured in units of k, watts/meter/degreeC.

    The lower the thermal mass of the shield, the faster it will come to thermal equilibrium - but if the temperature fluctuations in the system are large, then more thermal mass will help dampen the transients. It is similar in concept to adding RC to a circuit to increase the circuit time constant.

    Copper has a high thermal conductivity, as does aluminum. Steel has reasonable conductivity depending on the specific alloy and processing.

    Regards,

    Werner Metz