Some of the ideas associated with process control systems have already been discussed in §1.4. The majority of processes may be controlled automatically by adjusting the rate of flow of energy or material entering the process. In manually-controlled systems the human operator adjusts the rate of flow by means of a hand-operated valve; he will receive information regarding the state of the process from a measuring instrument giving a visual indication. Manual control has numerous disadvantages and indeed manual control of many modern plants would be virtually impossible, owing to their complexity and the speed and precision of control they require for successful operation.
KeywordsTransfer Function Process Control System Nyquist Diagram Automatic Process Control System Proportional Controller
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