How to install the German SICK temperature sensor?

When installing and using the German SICK temperature sensor, the following precautions should be taken to ensure the measurement effect:
1. Errors caused by improper installation of German SICK temperature sensors
If the installation position and insertion depth of the thermocouple cannot reflect the actual temperature of the furnace, in other words, the thermocouple should not be installed too close to the door and heating, and the insertion depth should be at least 8-10 times the diameter of the protective tube; The gap between the protective sleeve of the thermocouple and the wall is not filled with insulation material, which causes heat to overflow or cold air to invade the furnace. Therefore, the gap between the thermocouple protective sleeve and the furnace wall hole should be blocked with insulation materials such as refractory mud or asbestos rope to prevent cold and hot air convection from affecting the accuracy of temperature measurement; The cold end of the thermocouple is too close to the furnace body, causing the temperature to exceed 100 ℃; The installation of thermocouples should avoid strong magnetic and electric fields as much as possible, so thermocouples and power cable wires should not be installed in the same conduit to avoid interference and errors; Thermocouples cannot be installed in areas with little flow of the measured medium. When measuring the gas temperature inside a tube using a thermocouple, it is necessary to install the thermocouple in the opposite direction of the flow rate and make full contact with the gas.
2. Error introduced by insulation deterioration of German SICK temperature sensors
If the thermocouple is insulated, excessive dirt or salt residue on the protective tube and pull plate can cause poor insulation between the thermocouple and the furnace wall, which is even more severe at high temperatures. This not only causes loss of thermoelectric potential but also introduces interference, and the resulting errors can sometimes reach hundreds of degrees.
3. Error caused by thermal inertness in German SICK temperature sensors
Due to the thermal inertness of thermocouples, the indicated values of the instrument lag behind the changes in the measured temperature, which is particularly prominent during rapid measurements. Therefore, thermocouples with thinner thermoelectric electrodes and smaller protective tube diameters should be used as much as possible. When the temperature measurement environment permits, the protective tube can even be removed. Due to measurement lag, the amplitude of temperature fluctuations detected by thermocouples is smaller than that of furnace temperature fluctuations. The larger the measurement lag, the smaller the amplitude of the thermocouple fluctuation, and the greater the difference from the actual furnace temperature. When using a thermocouple with a large time constant for temperature measurement or control, although the temperature displayed on the instrument fluctuates very little, the actual furnace temperature may fluctuate greatly. In order to accurately measure temperature, thermocouples with small time constants should be selected. The time constant is inversely proportional to the heat transfer coefficient and directly proportional to the diameter of the thermocouple's hot end, material density, and specific heat. To reduce the time constant, in addition to increasing the heat transfer coefficient, an effective way is to minimize the size of the hot end as much as possible. In use, materials with good thermal conductivity and protective sleeves with thin wall and small inner diameter are usually used. In more precise temperature measurements, bare wire thermocouples without protective sleeves are used, but thermocouples are prone to damage and should be corrected and replaced in a timely manner.
4. Thermal resistance error of German SICK temperature sensor
At high temperatures, if there is a layer of coal ash and dust attached to the protective tube, the thermal resistance increases, hindering the conduction of heat. At this time, the temperature reading is lower than the true value of the measured temperature. Therefore, the external cleanliness of the thermocouple protection tube should be maintained to reduce errors.