Why are temperature thermistors and thermocouples armored?
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This post was last edited by wwxxss_1 on 2009-7-26 at 15:40, as the title suggests. Why is armoring needed? What is armoring? ?
Armoring is used to protect the primary temperature sensing element from corrosion, erosion, and other effects caused by fluids.
Armoring refers to the metal protective casing. Today’s thermal resistors and thermocouples are all armored; those that are not armored require special ordering. Moreover, it is difficult to make unarmored ones very thin in diameter; they are more labor-intensive to produce than armored ones, and their quality is hard to guarantee.
There are also unarmored ones; perhaps the designers thought they were too prone to damage
Some are not armored; I think there are several reasons for this: 1. To prevent decay and damage caused by movement of the materials during use; 2. To facilitate easy replacement at any time
Depending on the environment, different material requirements are needed for the shielding; of course, there are also special thermoresistors, such as those that are embedded, which are very small in size!
Thermocouple sheathing is used to protect the primary temperature sensing element from corrosion and erosion by fluids； Easy to inspect, maintain, repair, and replace!
An armored thermocouple is a solid cable-like assembly formed by combining a thermocouple wire, insulating material, and a metal sleeve. Compared to ordinary thermocouples, armored thermocouples have the following advantages: 1. Their outer diameter can be made very small, resulting in a low time constant, fast response speed, and minimal lag. 2. It has good mechanical properties and can withstand severe impacts and vibrations. 3. It can be bent arbitrarily, meeting the requirements of complex structural assemblies. 4. The thermocouple is covered by metal tubes and insulating materials, making it resistant to corrosion by harmful substances, and thus it has a long service life. 5. The insertion length can be chosen as desired; if the measuring end is damaged, the damaged part can be cut off, rewelded, and then used again. 6. It is easy to manufacture multi-point thermocouples, furnace tube surface thermocouples, micro thermocouples, etc. 7. It can be used as a temperature sensing element and installed inside the protective tube of ordinary thermocouples. Due to the above advantages, armored thermocouples are being used more and more often.
What was said upstairs was very comprehensive. Let me give an example: for one of the devices we use here, the design team initially specified ordinary explosion-proof thermoresistors. In practice, however, due to vibrations, these resistors would often break; those of poor quality wouldn’t even last a day, which caused a lot of trouble. It was later changed to an armored version, and it’s been fine for several months now.
Add a protective case; basically, if the thermistor fails, it can be replaced directly. It’s rare to go and cut off a little while it’s in use
We usually opt for armored thermometers only when they are exposed to impacts and vibrations, as the unfitted weld points are prone to breaking.