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The path between each state consists of some process (A through D) which alters the pressure or volume of the system (or both). Generalized PV diagram. A key feature of the diagram is that the amount of energy expended or received by the system as work can be measured because the net work is represented by the area enclosed by the four lines ...
Block diagram of a negative feedback control system used to maintain PV = SP Measurement of process variables is essential in control systems to controlling a process. The value of the process variable is continuously monitored so that control may be exerted.
A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large industrial control systems which are used for controlling processes or machines.
A feedback control loop is directly controlled by the RTU or PLC, but the SCADA software monitors the overall performance of the loop. For example, a PLC may control the flow of cooling water through part of an industrial process to a set point level, but the SCADA system software will allow operators to change the set points for the flow.
In cybernetics and control theory, a setpoint (SP; [1] also set point) is the desired or target value for an essential variable, or process value (PV) of a control system, [2] which may differ from the actual measured value of the variable.
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The PV diagram is a particularly useful visualization of a quasi-static process, because the area under the curve of a process is the amount of work done by the system during that process. Thus work is considered to be a process variable , as its exact value depends on the particular path taken between the start and end points of the process.
1970: L. S. Hill, Systems engineering in perspective, IEEE Trans. Eng. Manag., vol. EM-17, pp. 124-131, Nov. 1970.(presents a background on the evolution of the systems engineering process and attempts to synthesize a more complete resolution than was g enerally available in the literature.