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The cause of thermocouple skewed _ instrument

by:JVTIA     2020-10-28
Installed wrong deviation caused by such as placement of thermocouples and insertion depth means less than the real temperature of the reaction furnace, etc. , in other words, the thermocouple shouldn't be in too close to the door and heating, the depth of the insert should cover at least 8 ~ 10 times the diameter of the tube; Between the casing and the wall partition missing the cover of thermocouple insulation material overflow or cold atmosphere into the furnace heating, therefore between the thermocouple hole cover tube and furnace wall at leisure application of refractory mortar or insulating material such as asbestos rope jam to avoid cold and hot atmosphere convection and affect the accuracy of temperature measurement; Thermocouple cold end is too close to the furnace flow temperature 100 ℃; Thermocouple placement should probably avoid strong magnetic field and electric field, in order to not put the thermocouple and the power cable line in unity within the catheter in order to avoid introducing nuisance cause deviation; Thermocouples means less in few activities within the area measured medium, when the gas temperature with thermocouple measurement tube, must make the thermocouple placed against the velocity deviation. Insulation deterioration and the introduction of the deviation of thermocouple insulation, such as screen pipe and anchor plate too much dirt or salt slag between the thermocouple interelectrode and wall insulation fault, more serious at high temperature, this will not only cause the consumption of thermoelectric potential and will also introduce nuisance, deviation caused by accidental can reach 100 degrees. Thermal resistance high temperature deviation, such as screen pipe has a layer of ash, dust attached to the above, thermal resistance, growth of thermal conduction, when the temperature is lower than the true value of measured temperature value. Therefore, we should link pipe outside of the cover is clean, to reduce the deviation. Thermal inertia is introduced into the deviation due to the thermal inertia of thermocouple made meter indicating value is behind the change of the measured temperature, especially the impact when held fast measurement. Admitted to is what needs to be hot electrode is fine, screen pipe diameter smaller thermocouple. Temperature measuring situation allows, and screen pipe can be taken. Due to measurement lag, using thermocouples detect the amplitude of the amplitude of the temperature of the turbulence is temperature turbulence. After measurement, the greater the thermocouple, the smaller the amplitude of the turbulence and the reality of furnace temperature difference. When using time constant of thermocouple temperature or temperature control, the temperature of the instrument performance is turbulence is very small, but the reality of furnace temperature turbulence around a lot. To correct measurement of temperature, should choose the thermocouple time constant small. With thermocouple time constant is inversely proportional to the heat transfer coefficient, heat is directly proportional to the density and specific heat of the whole diameter, material, such as to reduce the time constant, in addition to the increased heat transfer coefficient, useful measure is just even to decrease the size of hot whole. Utilization of, usually takes the heat conduction performance is good material, thin, small diameter of the tube wall screen casing. In a fine temperature measurement, using no cover casing bare wire thermocouple, but a thermocouple is easy to damage, should be real-time correction and exchange.
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