A Web Guide About Temperature Sensors
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Types of Temperature Sensors
Key Pages

A large distinction can be made among temperature sensor types. From one perspective they can be simply classified into two groups, contact and non-contact. The two links below take you to descriptive pages on each type with a breakdown by more specific, detailed types. If you know the one you seek, use the links to the left to go directly to the page for a sensor type. There are also vendors of each type and some vendors sell more than one type. Start your search either for a specific type or go to the vendor page index and you can get to the vendors of specific types from there.

Both types of sensor require some assumptions and inferences to measure temperature. Many, many well-known uses of these sensors are very straightforward and few, if any, assumptions are required. Other uses require some careful analysis to determine the controlling aspects of influencing factors that can make the apparent temperature quite different from the true temperature.

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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".


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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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