Thermocouple is a commonly used temperature measuring instrument, which has certain application in many industries. All the instruments will have some faults in the process of using, and thermocouples are no exception. Leakage on thermocouple is a common fault, so how do we deal with it? Next, the technical staff of our company will give you a detailed introduction.
I. Reasons for Leakage on Thermocouples
(1) Refractory bricks on electric furnaces are not well insulated at high temperatures. Inserting thermocouples with metal tubes into the furnace wall with wire can easily make the furnace wire contact with thermocouples. Refractory bricks are good insulating materials at room temperature, but with the increase of temperature, the insulation performance will decrease significantly.
Alumina refractory bricks are mostly used in the lining of resistance electric furnaces, and their resistance value decreases significantly with the increase of temperature.
(2) When the furnace wire contacts the thermocouple, the platinum-rhodium thermocouple protective tube is alumina ceramic tube, and the insulating property of the couple wire is also reduced by wearing the ceramic tube as separation insulation at high temperature. At high temperatures, the insulation performance of refractory bricks decreases, resulting in leakage of electricity, which eventually leaks to the thermocouple, so that there is an AC leakage signal on the thermocouple.
2. Prevention of leakage on thermocouple
(1) Keep the thermocouple out of contact with the refractory bricks.
(2) Grounding the negative pole of the thermocouple to eliminate the leakage signal on the thermocouple.
(3) A filter is installed at the output end of the thermocouple.
(4) Ground wire grounding is induced from the thermal contacts of thermocouples.
(5) Apply coated heat-resistant steel tube or silicon carbide tube to the thermocouple tube and grounding it.
By using the above methods, it is ensured that the instrument can work normally under severe conditions, which ensures that the instrument can accurately point, control, record and play its due role.