Questions on SCADA and PLC

  1. What Is PLC ?

Answer :

PLC means [ Programmable Logic Controller ]. It is a class of industrially hardened devices that provides hardware interface for input sensors and output control element. The field I/p include element like limit switches, sensors, push button and the final control elements like actuator, solenoid/control valves, drives, hooters etc.

PLC Senses the input through I/P modules, Processes the logic through CPU and memory and gives output through output module.

  1. Applications Of Plc?

Answer :

PLC can be used in almost all industrial application solutions right from small machine to large manufacturing plants. Even it caters applications of redundant systems at critical process plants.

  1. Explain The Role Of Plc In Automation ?

Answer :

PLC plays most important role in automation. All the monitoring as well as the control actions are taken by PLCs. PLC Senses the input through I/P modules, Processes the logic through CPU and memory and gives output through output module.

  1. Explain The Role Of Cpu ?

Answer :

This component act as a brain of the system.

CPU consist of Arithmetic Logic Unit, Program memory, Process image memory, Internal timers and counters, flags It receives information from I/P device, makes decisions depending upon the information and logic written and sends information through the O/P devices.

The CPU’s are distinguished with following features:

Memory capacity

Instruction set supported

communication option

time required to execute the control program.

  1. Explain The Role Of Power Supply In Plc System ?

Answer :

Power supply provides system power requirement to processor, I/O and communication modules.

Typically the power supply has input voltage 120 V – 230 V AC or 24 V DC and back plane output current 2 A to 5 A at 5 V DC

  1. What are some different levels of SCADA machines and systems?

A: SCADA machines have several different forms. You can have field level devices such as sensors. You can have remote terminal units (RTUs), a main controller or “master station,” or you can have a simple computer system interface that displays data for the user.

  1. Why do companies use SCADA?

A: SCADA is a methodology that defines performance and protection of data for the plant or communication center. It helps improve productivity for employees and helps the economy save energy.

  1. What voltage does an RTU operate with?

A: A remote terminal unit operates at 110V/240V.

  1. Why would a company want to use a PLC over an RTU?

A: A programmable logic controller (PLC) is much cheaper and more flexible with programming. PLCs have been replacing RTUs because they are also easier to troubleshoot and have more sophisticated controls than RTUs.

  1. What is an HMI?

A: An HMI (human machine interface) is the system that connects to a SCADA database that displays data for the user. The HMI allows the operator to review diagnostic data and trending graphs.