What is the difference between ordinary thermocouple and armored thermocouple temperature instruments?

Weld two conductors or semiconductors A and B of different materials together to form a closed loop. When there is a temperature difference between the two attachment points 1 and 2 of conductors A and B, an electromotive force is generated between the two, thus forming a current of a certain size in the loop. This phenomenon is called the thermoelectric effect. Thermocouples work by using this effect.
If we use ordinary thermocouples, we must first have a certain understanding of these two types of thermocouples. Ordinary thermocouples are generally composed of thermocouples, insulating tubes, protective sleeves and junction boxes, while armored thermocouples are a solid combination of thermocouple wires, insulating materials and metal protective sleeves after assembly and stretching. However, the electrical signal of the thermocouple requires a special wire to transmit, which we call a compensation wire. Different thermocouples require different compensation wires, whose main function is to connect with the thermocouple to keep the reference end of the thermocouple away from the power supply, so that the reference end temperature is stable. 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 metal as the thermocouple. It is generally replaced by a wire with the same electron density as the thermocouple. The connection between the compensation wire and the thermocouple is generally very clear. The positive pole of the thermocouple is connected to the red wire of the compensation wire, and the negative pole is connected to the remaining color. Most of the general compensation wires are made of copper-nickel alloy.
Thermocouples are one of the most commonly used temperature detection elements in industry.
Thermocouple working principle
It is based on the Seebeck effect, that is, the two ends of two conductors of different components are connected to form a loop. If the temperature of the two connection ends is different, a physical phenomenon of thermal current is generated in the loop.
Its advantages are
High measurement accuracy. Because the thermocouple is in direct contact with the object to be measured, it is not affected by the intermediate medium. Wide measurement range. Commonly used thermocouples can measure continuously from -50 to +1600℃. Some special thermocouples can measure as low as -269℃ (such as gold, iron, nickel, and chromium) and as high as +2800℃ (such as tungsten-rhenium).
Simple structure and easy to use. Thermocouples are usually composed of two different metal wires, and are not limited by size and opening. They have a protective sleeve outside, which is very convenient to use.