PLC Structure: The PLC Structure mainly consists of a CPU, memory areas, and appropriate circuits to receive input/output data as shown in Fig. 21.22. A PLC can be considered as a box full of hundreds…
PLC Definition(Programmable Logic Controller or Programmable Controller): PLC Definition - Programmable Logic Controller (PLC) or commonly simply called a Programmable Controller, is a solid state, digital, industrial computer. It is a device that was invented…
Cascade Control with Digital Controllers: A simplified system to control the temperature of a process employing a gas burner using two Cascade Control digital controllers is shown in Fig. 21.21. Each controller has a number…
Digital Process Control: A digital process control functionally needs to operate in much the same way as a conventional analog controller. That is, it must provide facilities to raise or lower the set point and…
Direct Digital Control: Developments in digital electronics have led to many industrial processes being computer controlled. The first system used was Direct Digital Control (DDC), in which a computer measured each variable in the process,…
Choice of Electronic Signal Transmission: The range of air pressure used for Signal Transmission in pneumatic system is limited by the dynamic operating range of the pneumatic devices used. But the choice of electrical transmission…
Temperature Controls using an Analog Electronic Controller: A Temperature Controls scheme using an Analog Electronic Controller of Fig. 21.14 is as shown in Fig. 21.16. The temperature setting, derived from a slide wire, is compared with the…
Analog Electronics Process Controllers: An Analog Electronics Process Controllers must be capable of providing one or more of the three main methods of control, namely, Proportional, Integral and Derivative. The circuits described in this section…
Define Offset Error: Define Offset Error - Proportional control action is characterized by a permanent residual error in the operating point of the controlled variable when a change in load occurs. This error is called…
Proportional Controller: In many processes, the cycling that occurs with the two position ON—OFF control is undesirable. Steady process controlled in the absence of noises, is possible when the controlled variable is a continuous function…
