danw
Lifetime Supporting Member
If he does this as 2 wire, loop powered 4-20mA with a single power supply in the receiver panel (the conventional manner), then a 400 foot run is nothing to 4-20mA. Absolutely no signal loss.I would be concerned about the length of wire with any analog signal
I've seen 4-20mA cable runs of over a mile (1.6Km) at the mills that have run for years with no problem at all.
Conventional 4-20mA is VERY robust.
I have no idea if the 2 supply thing will even work, but to me it isn't worth bothering with because loop powered, 2 wire, passive 4-20mA transmitters were designed to work with a remote power supply at the receiver.
2 wire cabling runs from receiver panel to the field is the prime driver for 4-20mA; the wire break fault detection at 0mA is just a side benefit.