Difference Between SCADA and HMI

SCADA and HMI are control systems that are used in any organization. While SCADA refers to supervisory control and data acquisition, HMI is simply human machine interface. Industrial and infrastructure processes are normally monitored by computers. SCADA has applications in manufacturing, production, power generation, refining and many other sectors of economy and such control and monitoring can be continuous or discrete, as the requirement may be. Even facility processes in installations like airports, railway stations, ships and space stations make use of SCADA to monitor and control various processes.

A full fledged SCADA consists of many parts that are as follows.

HMI

This is used to connect with all the processes and then present this data to a human operator. Operator makes use of all the data and thus monitors and controls all the processes.

PLC

These are programmable logic controllers normally used as field devices. These are inexpensive and flexible devices.

RTU

These are remote terminal units that connect sensors used in the processes. They convert signals into digital data and send them to supervisory system.

Computer System

This is a supervisory system that gathers all the data and sends commands to the system.

It is clear from above that HMI is simply a part of SCADA. It is actually an interface between human and machine. Interface varies greatly from cell phones to nuclear reactors, and it is a challenge for the engineers to make interface simple, pleasant and interesting for human beings.

HMI is critical for the success of any SCADA as this apparatus provides all the data to a human operator. This input is analyzed by the operator to take decisions on the processes accordingly. HMI is associated with the databases of SCADA and provides information that is crucial for maintenance and troubleshooting. The operator usually receives information from HMI in the form of graphs or mimic diagram.