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A control loop is the fundamental building block of control systems in general and industrial control systems in particular. It consists of the process sensor, the controller function, and the final control element (FCE) which controls the process necessary to automatically adjust the value of a measured process variable (PV) to equal the value of a desired set-point (SP).
A major application of current loops is the industry de facto standard 4–20 mA current loop for process control applications, where they are extensively used to carry signals from process instrumentation to proportional–integral–derivative (PID) controllers, supervisory control and data acquisition (SCADA) systems, and programmable logic ...
Correct operation of the petrochemical process plant is achieved through the action of control loops. [1] These automatically maintain and control the pressure, temperature, liquid level and flowrate of fluid in vessels and piping. Control loops compare the measured value of a parameter on the plant, eg. pressure, with a pre-determined set point.
Stack light in automated production for in-line quality inspection. Stack lights (also known as signal tower lights, indicator lights, andon lights, warning lights, industrial signal lights, or tower lights) are commonly used on equipment in industrial manufacturing and process control environments to provide visual and audible indicators of a machine's status to machine operators, technicians ...
Its name comes from the information path in the system: process inputs (e.g., voltage applied to an electric motor) have an effect on the process outputs (e.g., speed or torque of the motor), which is measured with sensors and processed by the controller; the result (the control signal) is "fed back" as input to the process, closing the loop. [1]
There are several methods for tuning a PID loop. The most effective methods generally involve developing some form of process model and then choosing P, I, and D based on the dynamic model parameters. Manual tuning methods can be relatively time-consuming, particularly for systems with long loop times.
An example of a pure open loop control system is manual non-power-assisted steering of a motor car; the steering system does not have access to an auxiliary power source and does not respond to varying resistance to turning of the direction wheels; the driver must make that response without help from the steering system.
There were no allied vessels in the harbour so the indicator loops on the minefields were activated. Two hours later, at 23:32, current was detected in an indicator loop laid in a remotely controlled minefield, induced by the submarine as it passed over the cable. Activation of the loop detonated mines in the field, sinking the submarine. [10]