in reply to: Hart Multivariable Devices posted by John Osborne on 16 April 2009 at 05:57:45.
I think you will find that most HART devices report more than one variable by universal commands 3 or 9. Even a humble pressure transmitter also measures its local temperature (perhaps used internally for correction of the pressure cell's temperature dependence). Coriolis mass flow meters can offer density, viscosity and/or volume flow rate, as well as flow totals. Valve positioners report a multitude of diagnostic information. See each manufacturer's info for details ...