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information related to a specific interactive object in the unit screen. For example, the
operator can open text documents which explain the function of group starts, motors, and
valves. (ABB Inc. 2012b.)
By clicking on a dynamic object on the process screen, a faceplate appears. The faceplate
shows detailed information of the selected object, such as the current measured process
value and its range and alarm limits. Operators can also manually control the selected
object from the faceplate by setting the device on manual control, if allowed in the
programming. A faceplate of a control loop can be seen in Graph 8. The bottom buttons are
used to select a control method: automatic, manual or external control. The abbreviations
are MV = Manipulated Variable, SP = SetPoint, Dev = Deviation, and PI = Proportional
Integral. More detailed information about control loops can be found in section 4.1.2.
GRAPH 8. PI Control loop faceplate
Navigation between different menus is usually done by tabbed navigation. Tabs are located
at the top of the screen and provide quick access to important graphics. The tabs at
Freeport Cobalt are quick links to different plant sections, such as refining and chemicals
production. One could think of these as his favorite sites on an internet browser: this makes
it easy for a new user to relate to the operating system.