![]() ![]() ![]() In this case, the primary controller senses the level in a vessel, commanding the secondary (flow) controller to maintain the necessary amount of flow either in or out of the vessel as needed to maintain level at some setpoint. No attempt is made to arrange symbols in a SAMA diagram to correlate with actual equipment layout: these diagrams are all about the algorithms used to make control decisions, and nothing more.Ī sample SAMA diagram appears here, showing a flow transmitter(FT) sending a process variable signal to a PIDcontroller, which then sends a manipulated variable signal to a flow control valve (FCV):Ī cascaded control system, where the output of one controller acts as the setpoint for another controller to follow, appears in SAMA diagram form like this: The general flow of a SAMA diagram is top-to-bottom, with the process sensing instrument (transmitter) located at the top and the final control element (valve or variable-speed motor) located at the bottom. These diagrams focus on the flow of information within a control system rather than on the process piping or instrument interconnections (wires, tubes, etc.). SAMA is an acronym standing for Scientific Apparatus Makers Association, referring to a unique form of diagram used primary in the power generation industry to document control strategies. ![]()
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