A 100mA fuse would not protect the 20mA current source, what environment is the loop working in?
and over what distance?
also are you using screened cable on your loop cable.
to get 1A through 250 Ohm you need 250V. all 4-20mA loops are powered by much lower voltage such as 24V. at 24V even if sensor is short circuited, current will not exceed some 100mA.
to get 1A through 250 Ohm you need 250V. all 4-20mA loops are powered by much lower voltage such as 24V. at 24V even if sensor is short circuited, current will not exceed some 100mA.
sometimes people add fuse simply for convenience to test loop, not to protect it. when you plug multimeter across fuse and then open fuse, you can verify if reading of your device is correct without breaking the circuit. an example of situation where you would rather not break circuit is if data is logged or recorded.