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How to use thermocouples to play a greater role 


The errors introduced by the deterioration of the insulation, such as the insulation of the thermocouple, and the excessive dirt or salt slag on the maintenance pipe and the cable plate, cause poor insulation between the thermocouple poles and the furnace wall, which is more serious at high temperatures, which will not only cause the thermoelectric potential Loss and also introduce interference, the error caused by this can sometimes reach Baidu.
  Errors introduced by improper installation, such as the position and insertion depth of the thermocouple device cannot reflect the true temperature of the furnace, in other words, the thermocouple should not be installed too close to the door and the heating center, and the insertion depth should be at least the diameter of the maintenance tube 8~10 times; the distance between the thermocouple maintenance sleeve and the wall is not filled with insulation material, which causes heat overflow or cold air intrusion in the furnace, so the gap between the thermocouple maintenance tube and the furnace wall hole should be insulated with refractory mud or asbestos rope Material infarction.

In order to avoid the convection of cold and hot air affecting the accuracy of temperature measurement; the cold end of the thermocouple is too close to the furnace body to cause the temperature to exceed 100℃; The cable is installed in the same conduit to avoid introducing interference and causing errors; the thermocouple cannot be installed in an area where the measured medium is seldom active. When using a thermocouple to measure the gas temperature in the tube, the thermocouple must be installed against the direction of the flow rate, and sufficient Contact with gas.

Thermal resistance error At high temperature, if there is a layer of coal ash on the maintenance pipe and dust is attached to it, the thermal resistance will increase and the heat conduction will be hindered. At this time, the temperature indication is lower than the true value of the measured temperature. Therefore, the outside of the thermocouple maintenance tube should be kept clean to reduce errors.

The error introduced by the thermal inertia is due to the thermal inertia of the thermocouple, which makes the indicator value of the instrument lag behind the change of the measured temperature. This effect is particularly prominent when the rapid measurement is stopped. Therefore, thermocouples with thinner thermoelectrodes and smaller maintenance tube diameters should be used as much as possible. When the temperature measurement environment permits, the maintenance tube can even be removed.