What is the difference between RTDs ,thermistors and thermocouples?

Answer 1

RTDs are platinum wire resistors. Thermistors are semiconductor resistors. Both of these items respond to temperature by changing their resistance. Thermistors have relatively narrow ranges and are often used in temperature compensating circuits. Platinum RTDs have a much broader range and are used as temperature sensors up to 500°C (840°F) or more.

Thermocouples consist of two wires of different materials bonded together. A temperature difference between the bonded end and the free ends causes a voltage difference of a few millivolts between the two wires. Thermocouples are cheap and rugged. They're very popular for engineering tests because a technician with a couple of spools of wire can make dozens of them in a few hours. Response depends only on the wires used.

Answer 2

A thermistor is basically a resister that changes its value with temperature. A Thermocouple is a pair of two dissimilar metals twisted together. When this metal is heated, it generates very small voltage in order of milli-volts.

Thermistor is used in very narrow temperature range where as thermocouples can be used for subzero to as high temperature as the metal itself can stand. (although commercially manufacture red thermocouple does have range)

In a simple statement
Thermistors - resister
Thermocouples - voltage generator

Answer 3

http://www.omega.com/prodinfo/thermocouples.html
http://en.wikipedia.org/wiki/Resistance_temperature_detector
Click these to read about in detail
I use RTD's in our systems because of accuracy and speed response. There are basically two types pt 100 and pt 1000 that are available in many shapes. They are double the money but necessary in some applications. Thermistors are usually used in an application of a very narrow temperature range.
Thermocouple is widely used due to value and there are several types to accommodate application

Answer 4

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