Power Control and Switching Introduction Control of electric power, or power conditioning, requires the conversion of electric power from one form to another, that is, DC to AC, one voltage level to another, and so on, by the switching characteristics of various electronic power devices. Some of these devices, such as silicon controlled rectifiers (SCRs), […]
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Control and Instrumentation Technology
Servo Systems : Introduction , Principles of Operation , Compensator Design , Power Stage , Motor Choice , Gearing and A Simple Example Application
Servo Systems Introduction During the past 60 years, many methods have been developed for accurately controlling dynamic systems. The vast majority of these systems employ sensors to measure what the system is actually doing. Then, based on these measurements, the input to the system is modified. These concepts were initially used in applications where only […]
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Computer Control Systems : Distributed Control Systems (DCS) , Supervisory Control/Real-Time Optimization , Batch Control , Process Control Software , Digital Field Communications , Defining Terms and Further Information .
Computer Control Systems Distributed Control Systems (DCS) Microcomputer-based subsystems are standard in most computer control systems available today. The digital subsystems are interconnected through a digital communications network. Such systems are referred to as distributed digital instrumentation and control systems because of the network approach used to monitor and control the progress. Figure 18.63 depicts […]
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Advanced Control Techniques , Multivariable Control, Model Predictive Control , Feedforward Control , Adaptive Control and Autotuning and Statistical Process Control .
Advanced Control Techniques Although the single-loop PID controller is satisfactory in many process applications, it does not perform well for processes with slow dynamics, time delays, frequent disturbances, or multivariable interactions. We discuss several advanced control methods next, which can be implemented via computer control. One of the disadvantages of using conventional feedback control for […]
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Final Control Elements , Control Valves , Adjustable Speed Pumps , Feedback Control Systems , On-Off Controllers , Three Mode (PID) Controllers , Stability Considerations , Manual/Automatic Control Modes , Tuning of PID Controllers and On-Line Tuning .
Final Control Elements A final control element is a device that receives the manipulated variable from the controller as input and takes action that influences the process in the desired manner. In the process industries valves and pumps are the most common final control elements, because of the necessity to adjust a fluid flow rate […]
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Process Dynamics and Control : Introduction , Objectives of Process Control and Development of a Mathematical Model .
Process Dynamics and Control Introduction The field of process dynamics and control is concerned with the analysis of dynamic behavior of processes, process simulation, design of automatic controllers, and associated instrumentation. Process control as practiced in the process industries has undergone significant changes since it was first introduced in the 1940s. Perhaps the most significant […]
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Common Issues with PC-based Data Acquisition , The Low-Noise Voltmeter Standard , Proper Wiring and Signal Connections , Source Impedance Considerations, Pinpointing Your Noise Problems , Noise Removal Strategies , Signal Amplification , Averaging , Filtering , Grounding , Grounded and Floating Signal Sources and Types of Measurement Inputs .
Common Issues with PC-based Data Acquisition Aside from software and programming, the most common problem users run into when putting together DAQ systems is a noisy measurement. Unfortunately, noise in DAQ systems is a complicated issue and difficult to avoid. However, it is useful to understand where noise typically comes from, how much noise is […]
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Equivalent-Time Sampling : ETS Counter/Timer Operations , Hardware Analog Triggering , Factors Influencing the Accuracy of Your Measurements , Relative Accuracy , Integral Nonlinearity and Settling Time .
Equivalent-Time Sampling If real-time sampling techniques are not fast enough to digitize the signal, then consider ETS as an approach. Unlike continuous, interval, or multirate scanning, complex counter/timers control ETS conversions, and ETS strictly requires that the input waveform be repetitive throughout the entire sampling period. In ETS mode, an analog trigger arms a counter, […]
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Data Acquisition Software , Board Register-Level Programming , Driver Software , Real-Time Sampling Techniques , Preventing Aliasing , Software Polling , External Sampling , Continuous Scanning , Multirate Scanning , Simultaneous Sampling , Interval Scanning and Seamless Changing of the Sampling Rate .
Data Acquisition Software The software is often the most critical component of the data acquisition system. Properly chosen software can save you a great deal of time and money. Likewise, poorly chosen software can cost you time and money. A whole spectrum of software options exists, with important tradeoffs and advantages. Board Register-Level Programming The […]
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Data Acquisition : Fundamentals of Data Acquisition , Signals , Plug-In DAQ Boards , Types of ADCs , Analog Input Architecture , Basic Analog Specifications
Data Acquisition Fundamentals of Data Acquisition The fundamental task of a data acquisition system is the measurement or generation of real-world physical signals. Before a physical signal can be measured by a computer-based system, you must use a sensor or transducer to convert the physical signal into an electrical signal, such as voltage or current. […]
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