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temperature measurement problem base on sensortag

Hi, all.

I put sensortag in my office. I think the temperature of all objects except human body are almost the same as temperature of air. But no matter what objects I face to TMP006 very closely, like white paper, black bag, cup, wall and etc, the IR temperature from TMP006 is always 3-4°C lower than ambient temperature from SHT21. I think the data from SHT21 is right since it matches air condition setting. 

My question is if the temperature difference normal?

Many thanks!

  • Hello Rita,

    The Infrared Sensor Accuracy for TMP006 is +/- 3 C  (Max). So it might behave correctly.

    There is also a little info here in addition to the sensor data sheet and user guide:

    http://processors.wiki.ti.com/index.php/SensorTag_User_Guide

    Excerpt:

    Contactless IR Temperature Sensor

    The IR temp sensor temperature can measure the temperature of objects in front of the SensorTag with typical +/- 1C accuracy. The measurement distance depends on the size of the object to be measured. The datasheet recommends maximum distance of the radius/2. This means if the object has a radius of 1 meter, the distance from the object should be less than 50cm.

    Note that polished and shiny metal surface objects cannot accurately be measured with the IR temperature sensor. To understand the theory of operation and how to use IR temperature sensor please see TMP006 user guide and this document describing different lens materials.

  • Eirik V,

    Thanks a lot for your reply. It's very helpful. I didn't notice that the accuracy tolerance is as large as ±3°C.

    I keep TMP006 very close to the object like about 1 cm, so it is not the distance and FOV problem.