Correct installation and use of anticorrosive thermocouple

     The correct installation and use of thermocouple

     The correct use of thermocouples can not only accurately get the temperature value, to ensure product compliance, but also save material consumption of thermocouple, not only save money but also ensure product quality. Improper installation, thermal conductivity and time lag, and so on

     Main Error of Anticorrosion Thermocouple in Operation.

     1. Improper installation of the introduction of the error:

     In other words, the thermocouple should not be installed too close to the door and the heating place, the depth of the insertion should be at least 8 to 10 times the diameter of the protection tube; if the thermocouple is not installed, Thermocouple protection casing and the wall of the gap between the insulation material is not filled to cause the furnace heat spills or cold air intrusion, so the thermocouple protection tube and the gap between the furnace wall application refractory mud or asbestos rope and other insulating material plug to avoid hot and cold Air convection and affect the accuracy of temperature measurement; thermocouple cold side is too close to the furnace so that the temperature exceeds 100 ℃; thermocouple installation should be avoided as far as possible strong magnetic field and strong electric field, thermocouple and power cable should not be installed Thermocouple can not be installed in the area where the measured medium rarely flows. When measuring the gas temperature in the tube with a thermocouple, it is necessary to install the thermocouple in the direction of the flow velocity and contact with the gas adequately. .

     2. Insulation variation introduced by the error:

     Such as thermocouple insulation, protection tube and pull the line board too much dirt or salt residue resulting in thermocouple between the insulation between the furnace and the poor, more serious at high temperatures, which will not only cause the loss of thermoelectric power but also the introduction of interference, The resulting error can sometimes reach Baidu.

     3. Thermal inertial introduction of the error:

     Because the thermal inertia of the thermocouple causes the indication of the instrument to fall behind the change of the measured temperature, this effect is particularly prominent when performing rapid measurement. It should be possible to use a smaller thermocouple, the protection of the smaller diameter of the thermocouple. Permit the temperature environment, or even take the protection tube. The amplitude of the temperature fluctuation detected by the thermocouple is smaller than the amplitude of the fluctuation of the furnace temperature due to the measurement hysteresis. The greater the hysteresis, the smaller the amplitude of the thermocouple fluctuation, and the greater the difference with the actual furnace temperature. When the thermocouple with a large time constant temperature or temperature control, the instrument displays the temperature although the fluctuations are small, but the actual temperature fluctuations may be large. In order to accurately measure the temperature, a thermocouple with a small time constant should be selected. In order 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 side of the thermocouple inversely proportional to the heat transfer coefficient, the diameter of the thermocouple hot end, the density of the material and the specific heat . In use, usually with good thermal conductivity of the material, thin wall, the small diameter of the protective casing. In the more precise temperature measurement, the use of unprotected bushing bare thermocouple, but the thermocouple is easy to damage, should be corrected and replaced.

     4. Thermal resistance error:

     High temperature, such as the protection of a layer of coal ash, dust attached to the above, the increase in thermal resistance, hinder the conduction of heat, then the temperature indication lower than the true value of the measured temperature. Therefore, the thermocouple protection tube should be kept outside the clean, to reduce the error.