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TMP117: How to test the body temperature function by TMP117 on the production line

William Zhang2
Intellectual 905 points
Part Number: TMP117

Team,

Customer design a product to measure the body temperature of the human body using TMP117.

They have a concern that how to test the temperature function is normal or not in production line? 

What methods are generally used to test or calibrate the results on the production line？

Besides that, could you share some material like app notes which can  help customer design their product using TMP117 more efficient.

Thanks.

  • 0
    TI__Mastermind 43805 points

    Hi William,

    TI's production method is proprietary; I'm sorry I won't be able to share any details of our solution. 

    To make accurate temperature measurements, you need good thermal coupling between the sensor under test and the reference meter. The simplest way to do this is to submerge both in circulating liquid. See Fluke Calibration Baths or sous vide machines, for example. The liquid has better thermal conductivity than atmosphere. It completely surrounds and connects both sensors. It's relatively simple to create a large mass of liquid that is uniform in temperature using circulation. The large mass aids stability, as well. However, it's not practical to submerge products in production.

    We can use the properties of the circulating liquid as guidelines. 

    1. Thermal coupling. Instead of liquid, custom metal fixtures may be created to provide the best thermal connection between the sensor under test and reference meter. Air gaps should be avoided, and the sensor/meter should be as close together as possible.
    2. Thermal Uniformity. We can't aid thermal transfer in metal with circulation. We can only use the best materials, copper, and minimize the size of our fixture. If a test were attempted with air as the thermal conduction path, it might be helpful to circulate the air with a fan. Rule 1  Thermal Coupling would still limit the effectiveness of air.
    3. Thermal Mass. A metal fixture with a large mass will resist temperature fluctuations. A large mass may be easier to stabilize or hide noise from a temperature controller. You may decide to not attempt to control temperature at all and simply measure it. A large mass may help the sensor settle faster when it contacts it. However, there is a uniformity risk (rule 2) as the fixture grows. A fixture with a small mass that only couples the sensor to the meter (rule 1) should be higher priority than having a stable fixture temperature. 

    The following app note discusses thermal transfer for our devices. https://www.ti.com/lit/snoa967

    thanks,

    ren