An RTD or Resistance Temperature Detector is a device that produces a positive, predictable and nearly linear relationship between its temperature and its resistance value. It achieves this through a manufacturing process that deposits a thin platinum film element on a ceramic aluminum oxide substrate. An etching pattern is placed onto the RTD elements to create an electrical circuit. The main feature of the RTD element is a nearly linear relationship between its body temperature and its resistance value. It is the key characteristic that allows it to precisely measure temperature changes over a wide range of operating temperature changes. The RTD has radial, platinum plated nickel leads. Resistances range from 10 to 1,000 Ohms. Operating temperatures can range from -200 to 600 to -50 to 500 degrees C.

Littelfuse acquired U.S. Sensor Corporation in 2017 and manufactures thin film platinum RTD temperature detectors.