SPD for field instruments are installed by thread. The following contents need to be confirmed.
1. Number of wires to be protected
Select 2 wires, 3 wires, 4 wires accordingly.
2. Is there a backup electrical interface?
Yes——select parallel mounted SPD
No——select series mounted SPD
3. Check the type of the thread
The type of the thread needs to be specified, such as 1/2’NPT，3/4’NPT，which are commonly used.