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PLC vs SCADA: Understanding the Key Differences

plc scada industrial automation control system automation

This page compares PLC vs SCADA and mentions the difference between PLC and SCADA, including their basics.

The terms PLC and SCADA stand for Programmable Logic Controller and Supervisory Control And Data Acquisition, respectively.

Siemens PLC Siemens PLC

Following are the features of PLC:

  • It is a hardware or a controller or a device which is programmed and installed in a panel.
  • It is a special computer which is used to control machines and electromechanical processes in the industries.
  • There are different types of PLCs based on their applications. Figure-1 depicts PLC from Siemens. The other popular vendor is ABB.

SCADA system SCADA system

Following are the features of SCADA:

  • It is a computer system that collects and analyzes real-time data with the help of sensors.
  • The system is used for monitoring and controlling operations of a plant or equipment.
  • The SCADA system is composed of three main systems viz. MTU (Master Terminal Unit), RTU (Remote Terminal Units) & Human Machine Interface (HMI).
  • It is monitoring software installed on the PC which is used to monitor and control PLC.

Difference between PLC and SCADA

The following table summarizes the difference between PLC and SCADA.

FeaturesPLCSCADA
What is it?It is a solid state device which controls the output of the process through the program given in ladder diagrams.It is a software. It is used to monitor, control, and acquire data from field devices, even from remote locations.
Input/OutputInput and output are represented in normal open (NO), normal close (NC), and coil contacts.Input and output are represented in images.
Component/ObjectEach component involved is defined using an address.Each object is defined using a name.