FIGURE 8.1 Process and controller. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.2 Refrigerator/freezer system inputs and outputs. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.3 Continuous control of level. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.4 Discrete control of level. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.5 Composite continuous and discrete control. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.6 Objectives and subobjectives of a process. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.7 A discrete-control process. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.8 Completion of the initialization phase of the process shown in FIGURE 8.7. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.9 Basic flowchart symbols. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.10 Part of the initialization flowchart for FIGURE 8.7. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.11 Tank process for Example 8.4. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.12 Oven system for discrete control. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.13 Use of a relay and switch to start a motor. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.14 Use of momentary push-button switches and a relay to implement a latch. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.15 Symbols of input devices used in ladder diagrams. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.16 Symbols of output devices used in ladder diagrams. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.17 Symbols for switches used in ladder diagrams. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.18 Ladder diagram to control two lights. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.19 Elevator system for Example 8.6. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.20 Initialization to move platform down when the START button is pushed for Example 8.6. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.21 Ladder diagram for the STOP sequence of Example 8.6. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.22 The complete ladder diagram for Example 8.6. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.23 A simplified ladder diagram for Example 8.6. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.24 Solution for Example 8.7. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.25 Basic structure of the programmable logic controller (PLC). Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.26 Typical wiring to a PLC input module. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.27 Typical wiring to a PLC output module. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.28 PLC scan time puts restrictions on the speed of events. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.28 (continued) PLC scan time puts restrictions on the speed of events. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.29 Hand-held PLC programming unit. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.30 Desktop terminal PLC programming unit. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.31 Using an NC switch to turn on a light with relay logic and with PLC programming: (a) Wrong, the button turns the light OFF; (b) with relay logic, the button turns the light ON; and (c) with a PLC program, the button turns the light ON. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.32 Physical connections to the PLC (a) and the programmed ladder diagram (b) for a motor start/stop system. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.32 (continued) Physical connections to the PLC (a) and the programmed ladder diagram (b) for a motor start/stop system. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.33 Physical elements for Example 8.9. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.34 Wiring and program solution for Example 8.9. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.35 The basic PLC counter. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.36 Program and timing solution to Example 8.10. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.37 PLC timer functions: (a) simple timer, (b) accumulating timer. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.38 Solution to Example 8.11. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.39 Chemical system for Example 8.12. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.40 PLC program solution for Example 8.12. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.41 Tank system for Example 8.13. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.42 Physical ladder diagram for Example 8.13. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.43 Programmed ladder diagram for Example 8.13. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.44 System for use in Problems 8.8 and 8.14. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.45 Process for Problems 8.11 and 8.16. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.46 Motor and switches for Problem 8.15. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.47 System for Problems S8.1, S8.2, and S8.3. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 8.48 Hydroponic system for Problem S8.4. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.