Displays can be optimized by presenting information in a way that
increases situational awareness for operators. One way to create this
situational awareness is to provide operators with various levels of displays,
where each display level presents a different level of detail. ANSI/ISA
recommends four levels of displays, with level 1, or the overview level, having
the "broadest scope," and level 4 having the "most focused scope." These
varying levels of detail allow operators to view their entire scope of
responsibility and then drill down to increased levels of detail and control
functionality. Each display level presents the relevant information operators
need to perform their duties. The four levels are explained below.
- Level 1 (overview) displays
present an at-a-glance overview of the control process within an operator’s
scope of responsibility. These displays show the lowest level of process or
system detail. The information presented here aids operators in identifying,
processing, and comprehending the critical elements of a plant's operations.
- Level 2 displays allow the
operator to drill down into smaller portions of the areas they are responsible
for. These displays present information that aids operators in monitoring and
operating the elements they are responsible for on a daily basis. For example,
an operator may be responsible for operating multiple process units. Level 2
displays provide a process unit level overview for each of those units.
- Level 3 displays allow
operators to drill down into subsystems, showing a portion of a level 2 display
with an increased level of detail.
- Level 4 displays are used
for diagnostics and show equipment or systems related to level 3 displays in
greater detail, such as faceplates or detail displays.