TMP006EVM Software Use
5.5
Transient Correction Algorithm
The accurate performance of the TMP006EVM is highly dependent on a stable local temperature.
Degraded performance can be observed when local temperature transients are introduced into the
system, because the infrared (IR) thermopile in the TMP006 is sensitive to conducted and radiated IR
energy from below the sensor as well as radiated IR energy that comes from above the sensor.
When the TMP006EVM experiences a local temperature transient event, the PCB temperature and the
TMP006 die temperature drift apart from each other as a result of the thermal time constant of the
TMP006 thermopile. This difference in temperatures causes a heat transfer between the IR sensor and
the PCB to occur. Because of the small distance between the PCB and the bottom of the sensor, this heat
energy is conducted (as opposed to radiated) through the thin layer of air between the IR sensor and the
PCB below it. This conducted heat energy causes an offset in the IR sensor voltage reading, and
ultimately leads to unwanted temperature calculation error.
The additional error that results from local temperature transient events can be suppressed in the software
by using a transient correction algorithm. This algorithm monitors the TMP006 die temperature over a
four-second interval and uses the die temperature data to calculate a local temperature slope, as shown in
.
T
SLOPE
=
–
(0.3
×
T
DIE1
)
–
(0.1
×
T
DIE2
) + (0.1
×
T
DIE3
) + (0.3
×
T
DIE4
)
(1)
The local temperature slope and the known thermal resistance and capacitance of the TMP006 thermopile
are then applied to
to correct the sensor voltage reading.
V
OBJ_CORRECTED
= V
OBJ
+ T
SLOPE
×
2.96
×
10
–
4
(2)
The corrected sensor voltage value is then substituted for the raw sensor voltage, and the object
temperature is calculated using the normal methods.
To enable the transient correction algorithm, simply click the Transient Correction button in the
TMP006EVM GUI as shown in
. When transient correction is first enabled, a delay of four
conversions will be observed while the local temperature slope is being calculated.
Figure 17. Enable Transient Correction Algorithm
17
SBOU109A
–
May 2011
–
Revised October 2011
TMP006EVM User Guide and Software Tutorial
Copyright
©
2011, Texas Instruments Incorporated
