The most basic thermocouple construction is the wire type consisting of two dissimilar metals homogeneously joined at one end to form the measuring junction. All wire-type thermocouples have an exposed junction. While wire-type thermocouples offer good response time, ruggedness, and high temperature use, they are susceptible to environmental conditions and therefore must be protected. Mineral insulated thermocouples overcome the disadvantages of wire type construction by imbedding the thermocouple wires in ceramic insulation and protecting them with a metallic sheath. The mineral insulated cable (MI cable) design is based on small mass and high thermal conductivity which in turn promotes rapid heat transfer from the heat source to the measuring junction.The sheaths are impervious to most liquids and gases and withstand high external pressures. The seamless design protects against moisture or other contaminants attacking the thermocouple elements. Since the only materials used to make...
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