Armored thermocouple

　　Armored thermocoupleAs a temperature measurement sensor, it is usually used in conjunction with temperature transmitters, regulators, and display instruments to form a process control system, which is used to directly measure or control the temperature of fluids, steam, gas media, and solid surfaces within the range of 0-1800 ℃ in various production processes. Armored thermocouples have many advantages such as bending, high voltage resistance, fast thermal response time, and durability. Like industrial assembled thermocouples, they are commonly used as temperature sensors in conjunction with display instruments, recording instruments, and electronic regulators.

　　Armored thermocoupleDue to platinum being a precious metal, they are also known as precious metal thermocouples, while the remaining ones are called cheap metal thermocouples. There are two types of thermocouple structures, ordinary type and armored type. Ordinary thermocouples are generally composed of hot electrodes, insulating tubes, protective sleeves, and junction boxes, while armored thermocouples are a solid combination of thermocouple wires, insulating materials, and metal protective sleeves assembled and stretched. However, the electrical signal of a thermocouple requires a special type of wire for transmission, which we call a compensating wire. Different thermocouples require different compensation wires, which are mainly used to connect with the thermocouple and keep the reference end of the thermocouple away from the power supply, thereby stabilizing the temperature of the reference end. Compensation wires are divided into two types: compensation type and extension type. The chemical composition of the extension wire is the same as that of the compensated thermocouple. However, in practice, the extension wire is not made of the same material as the thermocouple, and is generally replaced with a wire with the same electron density as the thermocouple. The connection between the compensating wire and the thermocouple is generally clear, with the positive pole of the thermocouple connected to the red wire of the compensating wire and the negative pole connected to the remaining color. The material of most compensation wires is copper nickel alloy.

Armored thermocouples, like industrial assembled thermocouples, are commonly used as temperature sensors in conjunction with display instruments, recording instruments, and electronic regulators. They can also serve as temperature sensing elements for assembled thermocouples. It can directly measure the temperature of liquids, vapors, gas media, and solid surfaces in the range of 0 ℃~800 ℃ during various production processes. Compared with prefabricated thermocouples, armored thermocouples have advantages such as bendability, high voltage resistance, short thermal response time, and durability.

Due to the fact that the materials of armored thermocouples are generally expensive (especially when using precious metals), and the distance between the temperature measuring point and the instrument is far, in order to save armored thermocouple materials and reduce costs, compensation wires are usually used to extend the cold end (free end) of armored thermocouples to a temperature stable control room and connect them to the instrument terminals. It must be pointed out that the function of the thermocouple compensation wire is only to extend the thermoelectric electrode and move the cold end of the armored thermocouple to the instrument terminal in the control room. It cannot eliminate the influence of temperature changes at the cold end on temperature measurement and does not have a compensation effect. Therefore, other correction methods need to be used to compensate for the impact of cold end temperature t0 ≠ 0 ℃ on temperature measurement. When using armored thermocouple compensation wires, attention must be paid to model matching, polarity cannot be connected incorrectly, and the temperature at the connection end between the compensation wire and the armored thermocouple cannot exceed 100 ℃.