FIGURE 7.1 Elements of the final control operation. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.2 A process-control system showing the final control operations. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.3 An op amp circuit for Example 7.1. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.4 A pneumatic amplifier or booster converts the signal pressure to a higher pressure or the same pressure but with greater gas volume. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.5 Principles of the nozzle/flapper system. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.6 Using a nozzle/flapper for a current-to-pressure converter. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.7 The silicon-controlled-rectifier (SCR) symbol and characteristic curve. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.8 An SCR for variation of load voltage using the half-wave circuit. Only the positive half-source cycle delivers power to the load. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7. 9 A full-wave SCR circuit FIGURE 7.9 A full-wave SCR circuit. The effective rms dc voltage applied to the load is greater than that of the half-wave because the entire cycle is used. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.10 An optical coupler can be used to control triggering of the SCR from an external circuit. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.11 Circuit for Example 7.3. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.12 Voltages versus time for Example 7.3. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.13 Two common symbols for the Gate Turn-off (GTO). Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.14 GTO circuit for Example 7.4. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.15 A TRIAC can be triggered to conduct in either direction so a true ac voltage can be applied to a load. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7. 16 The DIAC has a bipolar breakover voltage, ±VL FIGURE 7.16 The DIAC has a bipolar breakover voltage, ±VL. After the voltage reaches ±VL, the DIAC conducts like a diode. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.17 The TRIAC can be triggered from the ac line using a DIAC. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.18 This modification of the triggering circuit eases calculation of a solution for Example 7.4. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.19 These are the voltage waveforms for Example 7.4. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.20 Bipolar Junction Transistor (BJT) symbol and characteristic curves. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.21 Operating the BJT in the linear mode. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.22 Operating the BJT in the switched mode. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.23 Power MOSFET symbol and characteristic curves. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.24 IGBT symbol and characteristic curves. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.25 A solenoid converts an electrical signal to a physical displacement. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.26 A solenoid used to change gears. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.27 Permanent magnet dc motor. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.28 Three dc motor configurations. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.29 A three-phase rectifier for high power dc motors implemented with SCRs. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.30 Simple ac motor with a permanent magnet rotor. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.31 The induction motor depends on a rotor field from current induced by ac field coils, as shown in FIGURE 7.30. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.32 ac motor control with a variable amplitude, variable frequency circuit using power electronics. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.33 An elementary stepping motor. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.34 The four positions of the elementary stepper rotor. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7. 35 Stepper with 8 rotor teeth and 12 stator poles FIGURE 7.35 Stepper with 8 rotor teeth and 12 stator poles. Note that the rotor teeth line up with the A poles. With the next step, the rotor teeth will line up with the B poles. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.36 A direct pneumatic actuator for converting pressure signals into mechanical shaft motion. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.37 A reverse-acting pneumatic actuator. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.38 A hydraulic actuator converts a small force, F1 , into an amplified force, FW . Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7. 39 A hydraulic servo system FIGURE 7.39 A hydraulic servo system. The process-control system provides input of the setpoint to the hydraulic servo. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.40 An example of a mechanical control element in the form of a hopper valve and conveyor. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.41 A continuous-operation paper-thickness-controlling system using mechanical final control elements. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.42 Basic control system for motor speed using a tachometer to sense the motor speed. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.43 A control system varies the rotation rate of a reaction kiln based upon temperature. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.44 Control of heat into a reaction vessel through an electrical power amplifier. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7. 45 A basic control-valve cross-section FIGURE 7.45 A basic control-valve cross-section. The direction of flow is important for proper valve action. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7. 46 A pneumatic actuator connected to a control valve FIGURE 7.46 A pneumatic actuator connected to a control valve. The actuator is driven by a current through an I/P converter. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.47 Three types of control valves open differently as a function of valve stem position. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.48 Feed control to a distillation column based on temperature. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.49 Figure for Problem 7.4. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.50 Figure for Problem 7.7. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.51 Figure for Problem 7.20. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.52 Figure for Problems S7.2 and S7.3. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 7.53 Figure for Problem S7.3. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.