Armored thermal resistance uses the characteristics of a substance that changes in temperature and its resistance changes with it to measure temperature. When the resistance value changes, the working instrument will display the temperature value corresponding to the resistance value. The armored thermal resistance is small in diameter, easy to bend, and has good shock resistance. It is suitable for installation where the assembled platinum resistance cannot be installed. Armored thermal resistance has the advantages of accuracy, sensitivity, fast thermal response time, stable quality and long service life.
In the manufacture of armored thermal resistance, firstly, the thermal resistance lead (usually pure nickel wire) is penetrated into the magnesium oxide insulating material, and then into the stainless steel protective tube together, and the armored heat is formed after multiple drawing and shrinking annealing. Resistance lead (equivalent to armored thermocouple material); then the thermal resistance temperature sensing element is butt welded with the armored thermal resistance lead that has been cut to the required length and the lead end is stripped; then the method of making the armored thermocouple is similar Finish the production of measuring terminal, terminal and installation device. Due to the large resistivity of the armored thermal resistance lead, there is no two-wire lead, generally three-wire lead, and the four-wire system needs to be specially noted. Because of the low temperature measurement of armored copper resistors, organic material insulation can be used instead of inorganic magnesium oxide insulation. The manufacturing process can be different from that of armored platinum resistors.
The armored thermal resistance can be used to measure the temperature in the range of -200~500℃, and the thermal resistance lead is connected to the secondary instrument for use. Because of its good electrical output characteristics, it can provide accurate temperature change signals for displays, recorders, regulators, scanners, data recorders and computers.
Features of armored thermocouple
Armored thermocouple is the most widely used temperature device in temperature measurement. Its main characteristics are wide temperature measurement range, relatively stable performance, simple structure, good dynamic response, and the ability to transmit 4-20mA electrical signals remotely, which is convenient for automatic control. And centralized control. In addition, the thermal response time is short, which reduces the dynamic error; it can be installed and used by bending; the measurement range is large; the mechanical strength is high and the pressure resistance is good.
The working principle of the armored thermocouple is that the two ends of the conductors of different components are welded to form a loop. The direct temperature measurement terminal is called the working terminal, and the terminal terminal is called the cold terminal, also called the reference terminal. When there is a temperature difference between the working end and the reference end, thermal current will be generated in the loop. Connect the display instrument, and the instrument will indicate the corresponding temperature value of the thermoelectromotive force generated by the thermocouple. The thermoelectromotive force will increase as the temperature of the measuring terminal increases. The magnitude of the thermoelectromotive force is only related to the material of the thermocouple conductor and the temperature difference between the two ends, and has nothing to do with the length and diameter of the thermoelectrode.