What is an RTD?
An RTD is a Resistance Temperature Device. This is a temperature sensor that has different properties than a thermocouple. Generally an RTD is made of a winding of a length of wire of an inert metal. The resistance to the flow of electricity of any conductor decreases with a decrease in temperature, reaching a superconductivity state at a temperature near absolute zero. The resistance increases as the temperature increases. A special class of RTD’s are made from platinum and are called PRT’s or Platinum Resistance Thermometers. This is the dominate form of the RTD sensor and as a result in normal usage, the term PRT and RTD are often used interchangeably.
An RTD is a resistance temperature detector, and is used to measure temperature by correlating the resistance of the RTD element with temperature. Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass core. The element is usually quite fragile, so it is often placed inside a sheathed probe to protect it. The RTD element is made from a pure material (i.e., platinum, nickel or copper) whose resistance at various temperatures has been documented. The material has a predictable change in resistance as the temperature changes; it is this predictable change that is used to determine temperature.
