Difference Between RTD and Thermocouples

As before:
WikiAnswers - What is the difference between thermocouple and RTD

The basic differences are:

(1) In thermo couple, the change of temperature is responded with change of voltage (in mV range), while in RTD the change of temperature is responded with change of resistances (in ohm)

(2) Thermocouple is an active element while RTD is a passive element and requires external voltage to measure the temperature

(3) Thermocouple has two leads, while RTD has 3 or 4 leads (additional compensation leads)

There are many links available in the internet for the details of the thermocouple and RTD. Here are some of them:

http://www.plasticservices.com/electrical/tcs-rtds.htm

http://www.sdiohio.com/Pages/Sensors.htm

- MS

There are 2-wire RTDs, but they are not as common as 3-wire or 4-wire versions.

Many if not most RTDs are 100Ω at 0°C, with the resistance increasing at higher temperatures. There are also 1000Ω RTDs. Thermocouples will typically have much smaller resistances than either of these.

The Omega Engineering catalog, probably available on line, has lots of good background information, as well as many selections of RTDs and TCs.

http://cr4.globalspec.com/thread/57886