Tag: Industrial control
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Benefits of Cascade Control
We know very well that closed loop control provides increased performance over open loop control. So it would be rational to expect benefits from adding inner control loop around plant items that have degrading overall performance. The Figure (a) below illustrates a typical example of a cascade control: In Figure (a) above, the outer loop…
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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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The Basics of Ladder Diagrams for Programming PLCs
The ladder diagrams are universally used as a symbolic and schematic way to represent the interconnection between the elements in a Programmable Logic Controller (PLC). The ladder network is also used as a tool for programming the operation of PLC. The elements are interconnected between the supply lines for each step in the control process…
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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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Basic Features of Distributed Control Systems (DCS)
In distributed control system, each process has its own separate controller located at the site. These local controllers are interconnected via a local area network so that all controllers on the network can be monitored or reprogrammed from a single supervisory computer. Once programmed, each process is essentially operating independently. Distributed control systems provides a…
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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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Types of Sensors used in Measurement and Process Control
A sensor is an element in a measurement system that detects the magnitude of a physical variable or parameter and changes it into a signal that can be processed by the system. The active element of a sensor is often referred to as a transducer. The monitoring and control systems require sensors to measure physical…
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Basic Facts about Data Acquisition (DAQ) and Process Control
The goal of most electronic systems is to measure or control some physical quantity. The system will have to acquire data from the environment, process this data and record it. As a control system, it will also have to interact with the environment. The flow of information in a typical data acquisition (DAQ) can be…
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Proportional-Integral-Derivative (PID) Control Systems
Proportional-Integral-Derivative For processes that are able to operate with continuous cycling, the relatively inexpensive two position controller is sufficient. For processes that cannot tolerate continuous cycling, a proportional controller is used. For processes that tolerate neither cycling nor offset error, a proportional plus integral/reset controller can be used. For processes that require improved stability and…