Ratio control

Most people  have likely had the experience of adjusting water temperature as they took a shower with dual valves: one valve controlling the flow of hot water and another valve controlling the flow of cold water. In order to adjust water temperature, the proportion of one valve opening...
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Supervisory control

In a manually-controlled process, a human operator directly actuates some form of final control element (usually a valve) to influence a process variable. Simple automatic (“regulatory”) control relieves human operators of the need to continually adjust final control elements by hand, replacing this task with the occasional adjustment...
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Ziegler-Nichols Tuning method

Ziegler-Nichols open-loop tuning procedure :- The first process tuned in simulation was a “generic” process, unspecific in its nature or application. Performing an open-loop test (two 10% output step-changes made in manual mode, both increasing) on this process resulted in the following behavior: From the trend, we...
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On-Off control sytem

Once while working as an instrument technician in a large manufacturing facility, a mechanic asked me what it was that I did. I began to explain my job, which was essentially to calibrate, maintain, troubleshoot, document, and modify (as needed) all automatic control systems in the facility....
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Closed loop control system

If liquid flow-control valve is opened in a step-change fashion, flow through the pipe tends to selfstabilize at a new rate very quickly. The following illustration shows a typical liquid flow control installation, with a process trend showing the flow response following a manual step-change in valve position:...
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