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IR Temperature Application

Bob Hensley
Prodigy 30 points
Other Parts Discussed in Thread: TMP006

I need to measure the temperature of a fluid inside 5mm x 5mm x 5mm quartz glass sampling tube.  If the spot radius is 5mm/2 = 2.5mm, the measurement distance for the TMP006 IR sensor is 2.5mm/2 = 1.25 mm.  This is the maximum distance for a 90% signal per the TMP006 User's Guide (SBOU107-May2011) pp6 Figure 3.  The sampling tube is enclosed in an insulated plastic housing.  Will the TMP006 function at this distance?

  • 0
    Prodigy 30 points

    Can I get a status update on this question?

  • 0 in reply to Bob Hensley
    TI__Mastermind 27715 points

    Hello Bob,

    The distance should not be a problem. While the maximum distance for 90% signal in your application is 1.25 mm given the recommendation in the TMP006 User's Guide, it's not absolutely necessary to have 90% signal absorption to get good measurement results. You can place the TMP006 further back from the target and calibrate the S0 coefficient (a gain error term) which will make up for losses due to distance.

    That being said, my concern with your proposed application is the IR transmittance/absorption behavior of the quartz and plastic materials you're using. The TMP006 only absorbs infrared energy in the 4 μm to 8 μm range, so any material between your target and the TMP006 must be mostly transparent in this range. Some plastics (such as polypropylene and polyethylene) meet this requirement, but not all are suitable. As for the quartz glass tube, fused quartz will only effectively transmit at wavelengths lower than 3.7 μm (example plot shown below from http://www.uqgoptics.com/materials_optical_irFusedQuartz.asp). Because of this, I do not expect the TMP006 to be an effective solution for your temperature measurement. A sensor with the ability to absorb shorter-wavelength IR energy will be required.

     

     

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Linear and Sensing Products 

  • 0 in reply to Ian Williams
    Prodigy 30 points

    Ian, thanks for the information.  I will change the glass to an IR type glass.  The glass type is IG2 glass that is made by Schott Glass.  It transmits 70 - 80 % in the 4 - 8 um range.

  • 0 in reply to Bob Hensley
    TI__Mastermind 27715 points

    Hi Bob,

    No problem. Thanks for sharing the tip on Schott Glass!

    For the benefit of the forum, here's a link to the IG2 glass data sheet: Infrared Chalcogenide Glass IG2

    Best regards,

    Ian Williams