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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.
The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a fieldbus or computer network that plugs into the PLC. The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control , distributed control systems , and networking .
This terminology is also used in complex analysis, as complex number can be desrcibed as vectors in the complex plane.Sources and sinks are associated with zeros and poles of meromorphic function, representing inflows and outflows in a harmonic function. A complex function is defined to a source or a sink if it has a pole of order 1. [14]
Example of SCADA used in office environment to remotely monitor a process. Both large and small systems can be built using the SCADA concept. These systems can range from just tens to thousands of control loops, depending on the application. Example processes include industrial, infrastructure, and facility-based processes, as described below:
In computing, a sink, or data sink generally refers to the destination of data flow.. The word sink has multiple uses in computing. In software engineering, an event sink is a class or function that receives events from another object or function, while a sink can also refer to a node of a directed acyclic graph with no additional nodes leading out from it, among other uses.
The "coil" (output of a rung) may represent a physical output which operates some device connected to the programmable controller, or may represent an internal storage bit for use elsewhere in the program. A way to recall these is to imagine the checkers (contacts) as a push button input, and the actuators (coils) as a light bulb output.
Memory-mapped I/O is preferred in IA-32 and x86-64 based architectures because the instructions that perform port-based I/O are limited to one register: EAX, AX, and AL are the only registers that data can be moved into or out of, and either a byte-sized immediate value in the instruction or a value in register DX determines which port is the source or destination port of the transfer.
Fan-out is ultimately determined by the maximum source and sink currents of an output and the maximum source and sink currents of the connected inputs; the driving device must be able to supply or sink at its output the sum of the currents needed or provided (depending on whether the output is a logic high or low voltage level) by all of the ...