Resistance Temperature Detectors (RTDs) are temperature sensors composed of certain metallic elements whose change in resistance is a function of temperature. As the name  implies, these are sensors used to measure temperature by correlating the resistance of the  RTD element with temperature. A small current is passed through pure electrical wire and voltage which is proportional to resistance, is measured and converted to units of temperature. Manufactured by winding a wire (wire wound elements) or plating a film (thin film elements) on a ceramic or glass core, it is sealed within a ceramic or glass capsule. RTDs offer a wide temperature range (-50 to 500°C for thin-film and -200 to 850°C for wire-wound), so selecting the proper element and protecting sheath material is important for functionality. Excellent degree of repeatability, stability and accuracy has made RTDs a common name in laboratory and industrial processes.