PASCO PS-2148 IR Sensor - Manual (Page 6)

IR Sensor Usage Notes
6 ®
and the sensor is irrelevant. Place the end of the fast-response
temperature probe in the cup close to the side that the IR sensor is
viewing.
Set up your computer or interface to calculate (T
s
4
– T
d
4
), and to graph
(T
s
4
– T
d
4
) versus thermopile voltage.*
Pour hot water (about 70
° C) into the cup. Leave some room for ice, but
make sure that the water surface is above the sensor’s field of view.
Start data collection.
After a few seconds, add a piece of ice to the cup and stir gently.
Continue to add ice, one piece at a time, while stirring, until the
temperature has decreased by 20 K or more.
Stop data collection.
Apply a linear fit to the graph of (T
s
4
– T
d
4
) versus voltage. The slope of
the best-fit line equals k.
Using this value of k, create a calculation of the form:
T = (k * V + Td ^ 4) ^ (1/4)
Where V is the thermopile voltage, and Td is the detector temperature.
Take IR data for an object of unknown temperature; T is the calculated
temperature of the object.
*T
s
is the temperature
measured by the
temperature probe;
T
d
is
the temperature
measured by the IR
sensor’s internal
thermistor.
For information on setting
up graphs, linear fits, and
calculations, refer to the
DataStudio Help menu,
or the Xplorer GLX
Users’ Guide.
Actual source temperature (top), detector temperature (middle) and voltage (bottom) vs. time as ice is
added to hot water