What we can learn about temperature and heat using
thermal sensing sheet
The thermal sensing sheet has several advantanges over
the more usual kinds of thermometers:
Temperature resolution: small changes in temperature
give rise to changes in color that the eye can detect
Spatial resolution: the color pattern shows how the
temperature varies from place to place, with details as small
as a millimeter visible.
Rapid equilibration: It doesn't take very much energy
to warm up the thermal sensing sheet, and so it very
quickly comes into equilibrium with the object it is
touching. The alcohol-in-glass thermometer takes
a minute to register a change in the temperature of the air;
the thermal
sensing sheet only needs a few seconds.
They can be used to measure the temperature of a very
small object, and to measure the temperature of the surface
of a solid object.
They are pretty, and unusual.
Of course, there are also disadvantages:
It isn't easy to turn a color into a number, and the
color depends on the viewing angle and on who
is viewing -- in particular, color blind people will
see the colors quite differently.
The range of the thermal sensing sheet is not very
wide. Unlike an alcohol thermometer that can be used
over a 200 Fo range, the thermal sensing
sheet is only useful over a 20 Fo range. At
other temperatures they don't tell us much at all.
The relationship between color and temperature will
change over time, because the chemicals involved are
slightly sensitive to air and water.
The thermal sensing materials
must be handled carefully, because
they are easily scratched, don't like to be left wet, and
will stick to things -- please see the
page about taking care of them.
Despite the disadvantages, we will see that they can be
valuable tools.