SCADA (Supervisory control and data acquisition) does the same thing what is mentioned above but it is a remote monitoring system where as HMI is local to machine. It means HMI would be mounted on control panel placed near by machines where as SCADA would be set up at a place far from the machines, generally the place known as Control room, Where you monitor the machine’s activities sitting in one place, you don’t need to come to near of machine to see what is happening in the machine.
Difference between SCADA and HMI
We can see the difference between HMI and SCADA in left hand side image. HMI is controlling individual machine or getting different events from the machine so the operator can know the status of the process or the different sensors of the machine. On the other hand, SCADA can includes all HMIs in the plant, more over it can control the whole plant. It can creates reports, can display trends etc.
The job of HMI is it to translate the signals and intentions from a human into signals of electric for the information system of machine to use. Therefore in doing so, lets the human operator to create interactive changes in the data and software process.
HMI its quite frequently has a display integrated into them as well to allow the operator to distinguish the relevant data to the action being carried out.
The HMI is just a part of the SCADA.
SCADA is a complete control system while the HMI is what the human operator works with.