HART - smart instrument /newbie questions


Thread Starter



I am trying to gett started in programming/configuration of DCS systems.

I understand the HART is back compatible on the legacy 4-20mA instrumentation wiring, sharing the pair of wires involved with older analog systems (in simple terms).

Does having a DCS capable of supporting HART I/O do any good if your instrumentation is not smart? Or do smart instruments just provide that much more information over a non-smart version?


Field Instruments can be "smart" without HART or any comm protocol. "Smart" also refers to the compensation and field rangeability that a smart transmitter can do versus those that aren't smart.

To answer your question:
If the field instruments are not HART, there is no advantage, even if DCS has HART capable I/O, other than the advantage of adding new field instruments, which are HART.

Q: Do smart instruments provide that much more info than non-smart?
Ans: Yes. 2nd, 3rd, and even 4th variables in addition to the primary variable, along with diagnostic information (max temperature exposure).

Since HART has been around for 20 years, many field instruments are HART compatible, but the HART capability hasn't been exploited other than in the initial setup (ranging & tagging) in older DCS's for lack of HART compatible I/O.


Jonas Berge - F

In my book a device got to have communication to be called "smart". Without communication it is only "microprocessor-based"

It is hard to believe that the instruments in the plant are not HART. Most instruments sold the past 10-15 years are HART although some are one of many
proprietary instrument protocols. I would really double-check if the devices have HART or not