When the temperature sensor is installed and used, the following items should be noted to ensure the best measurement effect:
1. The device is not properly introduced Equipment fault
such as the orientation and penetration depth of the thermocouple and compensation wire device cannot reflect the actual temperature of the furnace, in other words, the thermocouple and compensation wire should not be installed too close to the door and the heating area, puncture The depth should be at least 8 to 10 times the diameter of the protective tube; the distance between the protective sleeve of the thermocouple and the compensating wire and the wall is not filled with heat-insulating substances, which causes heat overflow or cold air intrusion in the furnace, so the thermocouple and the compensating wire protection tube and The open space between the furnace wall holes is blocked with refractory mud or asbestos rope and other insulating materials to avoid the convection of hot and cold air and affect the accuracy of temperature measurement; the cold end of the thermocouple and compensation wire are too close to the furnace body to make the temperature exceed 100 ℃; the thermocouple and The device of the compensating wire should avoid the strong magnetic field and the strong electric field as much as possible, so the thermocouple and compensating wire and power cable should not be installed in the same conduit to avoid introducing disturbance to form equipment failure; the thermocouple and compensating wire cannot The device is in the area where the measured medium is rarely moving. When measuring the temperature of the gas in the tube with the thermocouple and the compensation wire, it is necessary to make the thermocouple and the compensation wire reverse the direction of the flow rate, and touch the gas abundantly.
2. Equipment failure introduced due to poor insulation
If the thermocouple and compensation wire are insulated, too much dust or salt slag on the protection tube and cable board causes poor insulation between the thermocouple and compensation wire pole and the furnace wall It is more serious at high temperatures, which not only causes the loss of thermoelectric potential but also introduces disturbances, and the resulting equipment failures can sometimes reach Baidu.
3. The equipment failure introduced by thermal inertia
Because of the thermal inertia of the thermocouple and the compensating wire, the indication value of the appearance lags behind the change of the measured temperature. This effect is particularly outstanding when performing rapid measurement. Therefore, thermocouples and compensating wires with thinner thermal electrodes and smaller protective tube diameters should be used whenever possible. When the temperature measurement environment is agreed, the protection tube can even be removed. Because of the measurement lag, the amplitude of temperature fluctuations detected with thermocouples and compensation wires is smaller than the amplitude of furnace temperature fluctuations. The greater the measurement hysteresis, the smaller the amplitude of the thermocouple and the compensation wire shaking, and the greater the difference from the actual furnace temperature. When using a thermocouple with a large time constant and a compensating wire to measure or control the temperature, although the appearance of the temperature is very small, the actual furnace temperature may be very large. In order to accurately measure the temperature, thermocouples and compensation wires with small time constants should be selected. The time constant is inversely proportional to the heat transfer coefficient, and is proportional to the diameter of the thermocouple and compensation wire hot end, the density of the data and the specific heat. To reduce the time constant, in addition to adding the heat transfer coefficient, the most useful method is to minimize the hot end scale. In use, generally use materials with good thermal conductivity, thin tube wall and small inner diameter protective sleeve. In finer temperature measurement, bare wire thermocouples and compensation wires without protective sleeves are used, but the thermocouples and compensation wires are simply damaged and should be corrected and replaced in time.
4. Failure of thermal resistance equipment
At high temperature, if there is a layer of coal slag on the protection tube and dust is attached to it, the thermal resistance is added to prevent heat transmission. At this time, the temperature indication is more inverse than the measured temperature. Low code. Therefore, we should insist on cleaning the exterior of the thermocouple and compensation wire protection tube to reduce equipment failure.