in reply to: Multidropping hart devices. posted by Andrew on 21 February 2008 at 12:34:10.
I think this is fine.There is no particular spec for the parking current in devices used in multidrop mode. Manufacturers usually make it as small as they can. For loop-powered devices, 4mA is common, enough to provide power to the electronics, but it could be less or more. For active-source devices with their separate power supply, it could even be zero, but I expect the manufacturer has chosen 0.8mA, to allow the HART signal to be added without actually going into negative current (so simplifying the electronics).