Temperature is a physical quantity that characterizes the degree of hotness or coldness of an object, and it is a crucial and ubiquitous measurement parameter in industrial and agricultural production. Temperature measurement and control play a vital role in ensuring product quality, improving production efficiency, conserving energy, ensuring production safety, and promoting national economic development. Due to the widespread use of temperature measurement, temperature sensors rank first in number among all types of sensors, accounting for approximately 50%.
Temperature sensors indirectly measure temperature by observing how an object's properties change with temperature. Many materials and components exhibit properties that change with temperature, resulting in a wide variety of materials suitable for use as temperature sensors. The physical parameters of a temperature sensor that change with temperature include: expansion, resistance, capacitance, electromotive force, magnetic properties, frequency, optical characteristics, and thermal noise, among others. With the development of production, new types of temperature sensors will continue to emerge.
Because the temperature measurement range in industrial and agricultural production is extremely wide, ranging from hundreds of degrees below zero to thousands of degrees above zero, temperature sensors made of various materials can only be used within a certain temperature range.
The contact methods between temperature sensors and the measured medium are divided into two main categories: Contact and non-contact. Contact temperature sensors require thermal contact with the measured medium to ensure sufficient heat exchange and reach the same temperature. This type of sensor mainly includes resistive sensors, thermocouples, and PN junction temperature sensors. Non-contact temperature sensors do not require contact with the measured medium; instead, temperature is measured through the thermal radiation or convection of the measured medium. This type of sensor mainly includes infrared temperature sensors. The main advantage of this temperature measurement method is its ability to measure the temperature of moving materials (such as the bearing temperature of a slowly moving train or the temperature of a rotating cement kiln) and objects with small heat capacity (such as the temperature distribution within an integrated circuit).