When pneumatic field devices gave way to electronic 4 20mA many years ago
, it became much more practical to deliver process measurements over a long distance to a central point. This ushered in the age of the Distributed Control System (DCS). Roles were pretty well defined then. The maintenance technician was responsible for keeping a plant's field devices up and going. To do so, the maintenance technician spent a lot of tome in the field with some fairly straightforward test equipment. Of a good DVM was all that was needed. Meanwhile the control system engineer designed and implemented the plant's control strategy in the DCS computer. The plant operator ran the plant from what was hopefully a user friendly operator console. If the system was designed well, the plant operator was able to have full access to the key plant parameter while being restricted from changing things that might affect the actual operation of the control strategy.
With the introduction of intelligent field devices in the 1980s and protocol like HART, some of the configuration information for field devices was moved from the DCS out to the device itself. It was now possible for the maintenance technician to do things like set the device range and tag, calibrate the device in the field. PC-based packages were developed that would allow a user to look at and set these parameters remotely over the devices signal wires. Using these packages, many device problems could be diagnosed remotely from the control room or the maintenance shop.