TMP007 datasheet(15/55 Pages) TI

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TMP007

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SBOS685C – APRIL 2014 – REVISED JULY 2015

7.3.5 Calibration

The TMP007 default coefficients are calibrated with a black body of emissivity,

ε = 0.95, and an FOV (θ) = 110°.

Use these coefficients for applications where the object emissivity and geometry satisfy these conditions. For

applications with different object emissivity or geometry, calibrate the TMP007 to accurately reflect the object

temperature and system geometry. Accuracy is affected by device-to-device or object-to-object variation. For the

most demanding applications, calibrate each device individually.

As an overview the calibration procedure includes:

1. Defining the environmental variation range (die and object temperature range, supply voltage, temperature

change speed, sampling rate and so on).

2. Making the die temperature measurements and IR sensor voltage measurements over the environmental

range.

3. Generate an optimal set of coefficients based on the collected data set.

4. Load the coefficients into the TMP007 coefficients register. The object temperature register reflects the best

fit from the calibration process. Perform validation measurements because accuracy may vary over the

environmental range. If the object temperature measurement error is not acceptable, repeat the calibration

process using more environment points, data averaging, or narrow the temperature range of TDIE or TOBJ.

5. After a suitable set of coefficients is obtained, they can be stored in nonvolatile memory. Each coefficient

nonvolatile memory into the coefficient register.

The best temperature precision is available if every device is calibrated individually. Alternatively, if all the units in

the application use the same coefficients, then calibrate a statistically significant number of devices, and load

averaged coefficient values in nonvolatile memory.

Recalibration may be required under any or all of the following conditions:

1. Board layout changed.

2. Object or objects in the field of view changed.

3. Object distance or object surface changed.

4. Angle between device surface and direction to the object changed.

5. Object and local temperature range changed outside the environmental calibration range.

6. Object and local temperature transients significantly changed.

7. Supply voltage changed more than 1 V.

8. Air convection or conduction near the device changed.

For further information and methods for calibration, refer to SBOU142 — TMP007 Calibration Guide.

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