Resistance Temperature Detectors (RTDs)

Resistance temperature detectors (RTDs) are stable and have a wide temperature range. However, they are not as rugged and inexpensive as thermocouples. Since they require the use of electric current to make measurements, RTDs are subject to inaccuracies from self-heating.

An RTD operates on the principle that the electrical resistance of a material changes as its temperature changes. Resistance temperature detectors rely on the resistance change in a metal. The resistance will rise linearly with temperature.

Traditionally, RTDs use a length of conductor (platinum, nickel iron, or copper) wound around an insulator. Newer styles use a thin film of the conductor deposited on a ceramic substrate.

Resistance temperature detectors are used to measure temperatures from -196° C to 482° C (-320° F to 900° F).


  • Most stable
  • Most accurate
  • More linear than thermocouples


  • Expensive
  • Current source required
  • Low absolute resistance
  • Less rugged than thermocouples

Sensor Products for Process and Utility Customers

UE has a broad selection of standard temperature sensors that are designed for general industrial use. These range from small, fast-response designs for engine testing to 20-foot long multipoint assemblies for reactors. If you can sketch it, we can build it!


  • Heat recovery steam generator (HRSG)
  • Boiler tubes
  • Diesel engines
  • Turbine/reactor temperature sensing

Heat-Trace Resistance Temperature Detectors

When choosing a UE heat-trace RTD, installation is simplified, and maintenance expenses are reduced. Designed for use in any pipe or surface temperature measurement application, these sensors have:

  • ​NEMA 4 or explosion-proof heads
  • ​Heat transfer pad with excellent temperature response
  • ​Rugged stainless-steel sheaths for excellent mechanical protection
  • ​Replaceable element design for simplified RTD replacement — to replace a faulty element, simply remove the head cover, disconnect the leads, and remove the flexible element. Then insert the new element and reconnect the leads. The process is up and running in minutes.
  • Options include dual RTD sensors, thermocouple sensors, and a variety of weld pad and head styles
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