Originally Posted by daisizhou
But some external load modules have (CURRENT LOOP) (25 ohm, 75 ohm) and some don't 125 ohm, I don't know why
I think you may be mistaken (probably looking at the under side of one of the REM/ARM etc. modules).

Originally Posted by daisizhou
According to the conventional theory, an external load (CURRENT LOOP) should be connected, because this is the entrance to obtain the induced current
I can't see that you would want to involve the CURRENT LOOP sockets when using any of the load modules. So much for "conventional theory"!

If you don't inspect ... don't expect.