Page 61 - Programmable Logic Controllers, Fifth Edition - Mobile version

recorder. For example, suppose you are monitoring pres-
sure of a Pounds per Square Inch Gauge (psig) as shown GRAPHICS LIBRARY
The graphics library contained within an HMI develop-
in Figure 2-55. According to the table, you can see that it’s ment package provides buttons, lights, switches, sliders,
OK right now, but that’s all you know. This trend shows meters, fills, and other graphic objects (Figure 2-56). It
the pressure oscillating around a known good level. We saves design time by providing graphics and faceplates
may want to check on the cause of oscillation, but there for numerous industrial control devices that would other-
appears to be no immediate problem. wise have to be created manually. Librarian applications
may include easy-to-use features for resizing, changing
color scheme, and orientation of objects, as well as build-
Current Pressure Alarm Level Shutdown Level
ing your own graphics into the library.
235.2 psig 250 psig 300 psig

SELECT MODE
Shutdown
300
AUTOMATIC MOTOR STATUS
Alarm
250 MANUAL
MODE STATUS
AUTO Running
200

150
START STOP CONFIG MOTOR
100 MOTER MOTER SCREEN SPEED

50
Figure 2-56 Typical motor control graphics.
psig
2 Hrs.
Figure 2-55 Trend monitoring of a pressure gauge.

42 Chapter 2 PLC Hardware Components

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