| Remember
the fact that all sensor have errors in their readings. One key secret to high
quality measurement results is to have confidence in the error estimates. Neglecting
to make a careful error analysis often results in error much larger than the assumed
values, because assumptions are often unrealistic, missing one or more significant
contribution or not combining individual errors correctly. Also,
it is worth noting that all competent error analyses start with the uncertainties
assigned to the traceable calibration of the sensor itself. Without traceable
calibration, one is forced to make assumptions. (You know what the word ass|u|me
means, we hope.) Contact
Sensors
Contact temperature sensors measure their own temperature.
One infers the temperature of the object to which the sensor is in contact by
assuming or knowing that the two are in thermal equilibrium, that is, there is
no heat flow between them. Contact
sensors come in a wide array of types, sizes, measurement capabilities and prices.
There are numerous types but perhaps the best known are the thermometers used
in clinical or human body temperature measurements. Even these have a largely
increased number of subvariants today. From the glass with silvery mercury filling
(going away rapidly because of environmental and health damage that mercury can
cause), to the IR ear thermometer made popular by Braun's Thermoscan. Non-Contact
Sensors
Most commercial and scientific non-contact temperature sensors
measure the thermal radiant power of the Infrared or Optical radiation that they
receive and one then infers the temperature of an object from which the radiant
power is assumed to be emitted. IR thermometrs dominate this group but they have
their variations, too. One of the major differences are the Spot versus Area-measuring
IR thermometers. The latter are better known as quantitative or radiometric thermal
imaging cameras and they are usually used by skilled and trained operators called
"Thermographers". 
Click
here to
find out about ISPoT! The
Applications page can lead you to many well-known
solutions or examples, possibly similar to the one you are trying to solve. Why
re-invent the wheel?
Two excellent reference by Baker et al. are listed in the References
page and worth reading to get an idea of the complexities that can arise,
how to test and get around them. They are older books and while the technology
of the equipment has changed, especially the electronics, the measurement fundamentals
have not. Heat flow is heat flow. A great many temperature measurement problems
are solved through a good understanding of the heat flow involved in a specific
measurement situation. Surface temperature problems with contact sensors can be
solved in many cases through the use of non-contact sensors; they are almost ideal
for those types of applications and are in use in many industrial plants worldwide
in great numbers. Good
luck and best wishes. If you have some interesting success,
let us know and we'll help you share that with others who visit these pages.
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for visiting. | 