Thermal resistor measurement principle and main types

    Chinese name: Thermal resistor
　　English name: thermal resistor
　　Definition: A temperature detection element whose resistance value changes with temperature.
　　Thermal resistor is the most commonly used temperature detector in the medium and low temperature range. Its main features are high measurement accuracy and stable performance. Among them, platinum thermal resistor has the highest measurement accuracy. It is not only widely used in industrial temperature measurement, but also made into a standard reference instrument.
　　Working principle
　　The temperature measurement principle of thermal resistor is based on the property that the resistance value of a conductor or semiconductor changes with the change of temperature. Thermal resistors are mostly made of pure metal materials. Currently, platinum and copper are the most widely used. Now, materials such as nickel, manganese and rhodium have begun to be used to manufacture thermal resistors. Thermal resistors usually need to transmit the resistance signal through leads to computer control devices or other secondary instruments.
　　Main types of thermal resistors
　　(1) Proficient thermal resistors: The structure and characteristics of thermal resistor temperature sensing elements (resistors) commonly used in industry. From the temperature measurement principle of thermal resistors, it can be seen that the change of the measured temperature is directly measured by the change of the resistance value of the thermal resistor. Therefore, the change of the resistance of various wires such as the lead wire of the thermal resistor will affect the temperature measurement. In order to eliminate the influence of lead resistance, a three-wire or four-wire system is generally used.
　　(2) Armored thermal resistor: The armored thermal resistor is a solid body composed of a temperature sensing element (resistor), lead wire, insulating material, and stainless steel casing. Its outer diameter is generally φ2~φ8mm, and the minimum can reach φ1mm. Compared with ordinary thermal resistors, it has the following advantages: ① Small size, no air gap inside, small measurement lag in thermal inertia; ② Good mechanical properties, vibration resistance, and impact resistance; ③ Can be bent, easy to install ④ Long service life.
　　(3) End face thermal resistor: The end face thermal resistor temperature sensing element is wound with specially treated resistance wire and is tightly attached to the end face of the thermometer. Compared with general axial thermal resistors, it can more accurately and quickly reflect the actual temperature of the measured end face, and is suitable for measuring the end face temperature of bearings and other parts.
　　(4) Flameproof thermal resistor: The flameproof thermal resistor uses a specially structured junction box to confine the explosion of the explosive mixed gas inside its shell due to sparks or arcs to the junction box, so that the production site will not cause an explosion. Flameproof thermal resistors can be used for temperature measurement in explosion-hazardous places in Bla~B3c zones.