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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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FIGURE 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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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FIGURE 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 All rights reserved.
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FIGURE 7. 9 A full-wave SCR circuit
FIGURE 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 All rights reserved.
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FIGURE 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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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FIGURE 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 All rights reserved.
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FIGURE 7. 16 The DIAC has a bipolar breakover voltage, ±VL
FIGURE 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 All rights reserved.
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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 All rights reserved.
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FIGURE 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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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FIGURE 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 All rights reserved.
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FIGURE 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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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FIGURE 7. 35 Stepper with 8 rotor teeth and 12 stator poles
FIGURE 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 All rights reserved.
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FIGURE 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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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FIGURE 7. 39 A hydraulic servo system
FIGURE 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 All rights reserved.
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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 All rights reserved.
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FIGURE 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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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FIGURE 7. 45 A basic control-valve cross-section
FIGURE 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 All rights reserved.
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FIGURE 7. 46 A pneumatic actuator connected to a control valve
FIGURE 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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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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 All rights reserved.
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