Process control

Process control monitors and adjusts a process so its operation stays near desired conditions despite disturbances and changing demands.

Feedback control: A control method that measures a system’s output and adjusts its input to reduce the difference from a target. It is the central strategy for correcting deviations detected during operation.
Setpoint: A target value assigned to a controlled variable. The controller compares measured conditions with this target.
Distributed control system: A computerized control system whose functions are distributed among interconnected controllers and operator stations. It coordinates many process-control loops across large industrial plants.
Open-loop control: A control method that applies actions without measuring whether the desired output was achieved. It differs from feedback control because it does not correct errors from measured output.
Feedforward control: A control method that adjusts inputs in response to measured disturbances before they affect the output. It anticipates disturbances rather than waiting for feedback to reveal their effects.
Process variable: A measurable quantity describing a process condition, such as temperature, pressure, or flow rate. It is the condition monitored to determine whether operation meets its target.
Programmable logic controller: An industrial computer designed to automate machines and processes using programmed logic. It executes control sequences and interlocks in industrial operations.
Manual control: A control arrangement in which a human operator observes conditions and adjusts process inputs. It contrasts with automatic control, though operators often supervise automated systems.
PID controller: A controller that combines proportional, integral, and derivative actions to reduce control error. It is a widely used feedback algorithm for regulating continuous processes.
Sensor: A device that detects a physical quantity and produces a usable measurement signal. Its measurement supplies the information needed to assess process conditions.

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