Tag: instrumentation and control
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Feedforward Control
Feedforward control is based on principle of pre-emptive load counter-action i.e. if all major loads (i.e. disturbances) on a process variable are monitored, and their effects on that process variable are well-understood, a control system programmed to take the appropriate action based on load changes will shield the process variable (PV) from any adverse effect.…
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Solid-state Relays (SSR) Features and Operation
A solid-state relay (SSR) is a purely solid-state device used for turning ON and OFF AC loads such as motors. Features of a Solid-state Relay Let’s consider the figure below: Physically, the SSR is packaged in a box with four electrical terminals: two input terminals and two output terminals. The input or control voltage of…
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What is Motion Control?
Motion control generally refers to an open loop or closed loop electromechanical system in which things are moving. A motion control typically consists of a motor, mechanical parts that move and often feedback sensor(s). Typical examples of motion control applications are: Servomechanisms Numerical control machines Industrial robots Variable speed drills Digital torque wrenches Hard-drive head-positioning…
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What is Sequential Control System?
This is a control system that manages a process defined by a series of tasks to be performed i.e. a sequence of operations, one after the other. Each operation in the sequence is performed either for a certain period of time (in which case, it is time-driven), or until the task is finished e.g. as…
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What is Process Control?
Process control can be defined as a control system that manages a particular industrial process so that a uniform, correct output is maintained. It does this by monitoring and adjusting the control parameters such as the flow rate or temperature to ensure the output product remains as it ought to. A typical example of process…
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Basic Features of Programmable Logic Controllers (PLCs)
Introduction to Programmable Logic Controllers What is a Programmable Logic Controller? A PLC is a user friendly; microprocessor-based specialized equipment that carries out many types of control functions with levels of complexity for use in industrial automation applications. Its objective is to monitor crucial process parameters and adjust process operations accordingly. A PLC can be…
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What is the Controller?
A controller is a device that generates an output signal based on the input signal it receives. The input signal is actually an error signal, which is the difference between the measured variable, and the desired value, or setpoint. The input error signal represents the amount of deviation between where the process system is actually…
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The Operation of a Temperature Control System for lubricating oil
Lubricating oil reduces friction between moving parts and also removes heat from the components. As a result, the oil becomes hot. This heat is removed from the lubricating oil by a cooler to prevent both the breakdown of the oil and damage to the mechanical components it serves. The lubricating oil cooler consists of a…
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Feedback Control System
The basic elements of a feedback control system are represented by the block diagram below. The functional relationships between these elements are also shown in the diagram. The block diagram represents flow paths of control signals but do not represent the flow of energy through the system or process. The plant is the system or…
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Principles of Control Systems
A control system is a system of integrated elements whose function is to maintain a process variable at a desired value or within a desired range of values. The control system monitors a process variable or variables, and then causes some action to occur to maintain the desired system parameter. A good example in a…