The measurement and control of temperature is an important part of refractory material production, and the quality of kiln temperature control will directly affect the product quality. Especially for tunnel kilns, they have the characteristics of multiple temperature measurement points and long continuous working time. If the temperature parameters are not well controlled, it will bring significant economic losses to the production enterprise. Therefore, choosing appropriate temperature measurement methods is an important link to ensure the normal operation of the kiln.
There are two traditional temperature measurement methods for tunnel kilns: one is to use thermocouples for temperature measurement, which is characterized by high temperature measurement accuracy and can be connected to paperless recorders or control systems for closed-loop control. Its disadvantage is short service life, especially in 1300℃The thermocouple consumption on the above high-temperature kilns is extremely high, and the price is also expensive, resulting in high equipment operating costs; The second method is an optical pyrometer, which measures temperature based on the color of the object being measured. As it does not directly contact the high-temperature zone, it has a long service life, but the measurement accuracy is low, and it is also affected by human factors, resulting in poor authenticity. The application of infrared thermometers can effectively overcome the above disadvantages.
Paperless recorders have high measurement accuracy and can output electrical signals like thermocouples for automatic recording and control. They also have the advantages of long service life, simple operation, and low human error. Therefore, infrared thermometers are ideal temperature measuring instruments for high-temperature tunnel kilns. In the application of infrared thermometers in tunnel kilns, there are two commonly used solutions based on different user requirements: single point temperature measurement and multi-point switching temperature measurement.

They are introduced as follows:
Single point temperature measurement system: Each temperature measurement point is composed of a probe and an instrument box, and the temperature measurement unit collects temperature. Then connect the 4-20mA analog signals output from each unit instrument box to a multi-point recorder or control actuator, and communicate data with devices such as computers and printers through the RS-232 port. The temperature measurement unit in this system usually uses instruments with high accuracy and strong functionality.
Switching temperature measurement system: This system connects the infrared probe signals installed at each temperature measurement point to a thermometer for signal processing. And output 1-5V temperature signals corresponding to each temperature measurement point for recording by multi-point recorders. At the same time, the temperature data can be directly input into the computer through the RS232 port for analysis and processing. It can also be directly printed out by connecting to a printer.
In the above two schemes, the single point temperature measurement system has an independent temperature measurement and signal processing system for each temperature measurement point, and its output analog and digital signals are real-time continuous signals with fast response speed. It can be used as a real-time control signal for the control actuator to achieve closed-loop control. The multi-point switching temperature measurement system, although its output analog signal is also continuous, has a certain lag with the real-time temperature value, so it can only be used for data acquisition and recording, and should not be used as a control signal. Its advantage is that it has a good cost-effectiveness and can reduce equipment costs in situations where the usage requirements are not too high.
In the use of other refractory kilns, such as reverse flame kilns and angular kilns, single point temperature measurement schemes are more commonly used due to the limited number of temperature measurement points. There are also handheld infrared thermometers used, but this instrument can only intermittently measure the temperature of the kiln, and each measurement record must be manually operated, which cannot achieve automatic continuous measurement.