HART-only device connected to HART AI channel

[123MB]

Has anyone ever connected a HART-only device (i.e. without 4-20mA) onto a HART AI module?

 

[danw2]

No. It's not a functional concept.

The FSK modulated HART signal is superimposed on the current signal.

HART infers a current signal as well. For point-to-point, it's a 4-20mA signal. For multidrop, it's 4mA fixed. But there's always a current signal.

 

[roydm]

Why not just make a dummy current loop using fixed resistors then add the FSK Hart signal in series. The total loop resistance could be about 2k with the HART imposed over a fraction of that. You might have to experiment a little, perhaps some small capacitors to couple the signal across the resistance.