About Resistance Temperature Detectors-(RTDs, PRTs, PRT100 & SPRTs)
Resistance Temperature Detectors fall into three basic types: Platinum Resistance Thermometers (PRTS), Standard Platinum Resistance Thermometers (SPRTS) and base metal RTDs, the latter being commercially available in both copper and nickel types.
They are also available in several different forms of construction ranging from wire-wound to thin film devices.
RTDs are used to measure temperature based on the temperature sensitivity of the metal used in its construction.
This sensitivity is known as the temperature coefficient of electrical resistance. Platinum is the principle metal used in science and industry for temperature measurements requiring precision on the order of 0.1 °C, or slightly better.
PRT100 is among the most common type of commercial platinum resistance thermometer having a reference resistance of 100 ohms at 0 °C.
Information web pages on them are on About Temperature & Moisture Sensors, A Web Guide with organized links to resources on the web that explain the background and operation of platinum RTDs as well as nickel and copper devices.