Smart Transmitter and Conventional 4-20 Ma
Smart Transmitter and Conventional 4-20 Ma
Smart Transmitter and Conventional 4-20 Ma
produce 4-20 mA analogue signal as well as it can produce digital signal (such as output, command/status
indication).
Not necessarily smart transmitter should have analogue output. But continuing popularity & investment in existing
4-20 mA current transmission compel manufacturer to include analogue output. Also delay in developing an
international digital fieldbus standard, forces manufacturer to make smart transmitter part analogue/part digital. One
of the prominent digital signal protocol is HART (Highway Addressable Remote Transducer)
Because of greater sales volume sometimes smart transmitter are cheaper than traditional ones. In many cases smart
transmitters are only used in a conventional (non-smart) way on two output wire. Foundation Fieldbus transmitters
are also smart but it can not produce analogue output signal(probably). So you need special arrangement in your
control system so that controller can extract information from the digital signal produced by transmitter.
Hello,
As a member of the PMCD division, I was looking on the ISA Web site to find
a technical paper explaining the pros and cons (technical and financial) of
using smart instrument technology vs traditional 4-20mA in the industrial
process industry, and until now I could not find any. As consulting
engineers in the power plant industry (among others), we are looking for
some kind of study made on the plus and minus of having the design made with
smart instrumentation, from our point of view (designers) and from the
client point of view (users).