Thermocouple is a kind of common temperature measuring instrument, the application scope is very broad, in petroleum, chemical industry, metallurgy, machinery, and other industries have a certain application. Thermocouple leakage reason ( 1) On the furnace refractory at high temperature insulation fault, equipped with wire furnace furnace wall inserted with metal wire contact with thermocouple, thermocouple is easy to make furnace refractory brick is a good insulating material, at room temperature but as temperatures rise, insulation performance will decline significantly. Resistance furnace lining with alumina refractory brick for the most part, its resistance value also significantly reduced with temperature rise. ( 2) Furnace wire contact with thermocouple, platinum, rhodium thermocouple protection tube is alumina ceramic tube, accidentally silk made separation insulation porcelain tube wear, under the high temperature insulation performance also want to reduce, cause leakage, after the leak to the thermocouple, so there is ac leakage on the thermocouple signals. The thermocouple on the leakage solution ( 1) Keep the thermocouple is not in contact with the refractory brick. ( 2) The thermocouple negative ground, eliminate the leakage on the thermocouple signal. ( 3) Add filter on the thermocouple output end device. ( 4) From the hot junction thermocouple leads to earth ground. ( 5) On the thermocouple tube and jacket heat-resistant steel pipe or carborundum tube, and make it grounded.