Tungsten-Rhenium Wire Problems in Useing

1 Errors Introduced by Improper Installation

Thermocouples should be mounted too close to the door and the heated places, insertion depth should be at least the diameter of the protective tube 8 to 10 times , and the insertion depth of the installation position does not reflect the true temperature of the furnace . Thermocouple protection tube with intramural interval Unfilled adiabatic material , resulting in overflow hot or cold air furnace , so the thermocouple protection tube and the gap between the furnace wall hole applications such as refractory cement or asbestos insulating material clogging rope to avoid hot and cold air convection and affect the accuracy of temperature measurement . Thermocouple should be installed as far as possible away from strong magnetic fields and strong electric field, thermocouple and power cables should not be wire-bound with a catheter in order to avoid the introduction of interference caused by errors. Thermocouples can not be installed in measured media rarely flows in the region, when measured with a thermocouple tube gas temperature must be going against the flow direction of the thermocouple installation , and full contact with the gas .

2 Error Introduced Insulation Deterioration

Such as thermocouple protection tubes and pull plates excessive dirt or salt residue resulting thermocouple very poor insulation between the wall of the furnace at high temperature is more serious , it will not only cause the loss of thermoelectric power but also the introduction of interference , resulting the error sometimes up on Baidu .

3 the Error Introduced by the Thermal Inertia

As the thermal inertia of the thermocouple indication value of the instrument behind the measured temperature changes , while a fast measurement of this effect is particularly prominent. It should be possible using the hot electrode smaller, smaller diameter thermocouple protection tube . Temperature environment permit, or even take away the protective tube . Because of measurement hysteresis , thermocouple temperature fluctuation of the detected temperature fluctuation amplitude is small amplitude . Measuring lag larger the smaller the amplitude of fluctuation thermocouple , the greater the difference between the actual oven temperature . When a large time constant thermocouple or temperature control , the instrument displays the temperature fluctuation is small though , but the actual oven temperature fluctuations may be significant. To accurately measure the temperature , time constant should be selected thermocouple . The time constant and the heat transfer coefficient is inversely proportional to the diameter of the thermocouple hot end , and the material density is proportional to the specific heat , such as to reduce the time constant , in addition to increasing the heat transfer coefficient , the most effective way is to minimize the size of the hot end . Use, usually good thermal conductivity materials, thin wall, small diameter protection tube . In the more precise temperature measurement, the use of non- bare wire thermocouple protection tube , but the thermocouple easily damaged, should be promptly corrected and replaced.


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