What's the difference between SCADA and HMI?


Thread Starter


Can anyone explain what is the difference between SCADA and HMI systems?
Are they the same?

as far as i Understood HMI are more like Operator Panel in front of the machine or process and SCADA do the same function but centralize all PLC's around the whole production line.

Is this statement correct??

Thank you folks

These are very fuzzy terms these days. However, the rule of thumb is that, when the sensing and control system involves large distances (in kilomerters), the system is called SCADA. Usually there is local control at each individual entity (RTU) and a very small amount of control from main control system (mostly known as HMI). HMI is basically the human machine interface. It is part of all systems, whether distances are large or small.
i think it is. SCADA (Supervisory Control & data acquisition) allows networking from lower process level to management level which consists of HMI.

Saeed Beheshti Maal

Generally SCADA should have an HMI for operator interface but this is not the case for HMI, as HMI not always include control functions and may be limited to monitoring capabilities only.
Yeah, I think your definition is close.

HMI vendors like to imply they are SCADA systems, so their is some confusion. The SC in SCADA is for Supervisory Control. This means there is something above basic PID control. Some intelligence is added to optimize the whole process.

Maybe the words used to create the acronym will provide some assistance. Supervisory Control And Data Acquisition or Human Machine Interface.
HMI is much wider then SCADA. The IEC defines HMI as: "where people and technology meet. This people-technology intercept can be as simple as the grip on a hand tool or as complex as the flight deck of a jumbo jet."

For process control:
SCADA is a category of software application program for process control and therefor also an HMI-system. On the other hand: HMI-systems include not only SCADA, but also local panels with push-buttons and lamps.
SCADA is a very broad term in today's process control arena.

SCADA is an acronym for supervisory control and data acquisition. There are many "SCADA" programs on the market. A SCADA program will allow you to integrate horizontally across the plant floor and upwardly into management information systems. One of the best "SCADA" programs on the market today is called "Wonderware". At least they boast of the largest market share. Others are IBM's Plant Floor, Intellusions, Allen Bradley's RS View and a few others.

HMI, an acronym for "Human Machine Interface" formerly known as MMI and is still used is an acronym for "Man Machine Interface". These packages usually incorporate hardware and software applications and are used as an interface between an operator and a machine or process control. I like to think of a HMI as a graphical interface to a PLC or other control solution. A touch screen control, which allows the operator to use the screen of a computer or other types of monitors to turn things on and off and set parameters as well as view fault routines is a good example of HMI.