A thermocouple is a sensor for measuring temperature. It consists of two dissimilar metals, joined together at one end. When the junction of the two metals is heated or cooled a voltage is produced that can interpreted by a temperature controller, high limit or display device. There are two common constructions for these: Tube and Wire and Mineral Insulated. The tube and wire uses an empty stainless tube with a wire inside which has a welded tip incorporating the wire junction. This construction is typically used to 480ºC. The Mineral Insulated construction uses a highly compacted stainless sheath with solid conductors encased in magnesium oxide insulation. This construction offers a wider variety of diameters, allows for the sensors to be bent in the field and for temperatures to 1200ºC. These sensors are available is a huge range of physical packages with a variety of lead wire, housing, and mounting options.