What is the difference between HMI and Scada system?

SCADA stands for “Supervisory Control And Data Acquisition,” which is an integrated system that is used to control and monitor the workings of the individual parts of the plant. The SCADA often controls pumps, fans, and other machinery along with their other characteristics. The controlling mechanisms are electronic circuits known as Programmable Logic Circuits or PLCs. The PLC controls the machine as well as polls the sensors for data. The data is then sent to the control room. In the control room, the operator needs to make sense of the data as well as issue commands like turning the machines on or off. This is where the HMI, or Human Machine Interface, comes in. The HMI is usually a graphical layout of the entire system showing on a device having a TFT display with gauges, lights, and controls situated in the corresponding locations of the machines. The gauges show the normal range of operation as well as the abnormal range so that the operator knows if the equipment is within the accepted operating range. The lights may indicate if the machine is working or not, as well as the occurrence of faults. The controls send the instructions to the PLC, which in turn control the whole system.

Although all above answer gave right answer , howver I wil siplfy it like this:

HMI : Human Machine Interface, It's an interface betwen the operator and local devices (machine) to make some change to a variable or edit the process of the machine.

In other side SCADA aprev. of supervisory control and data acquisition , It's a system that assembly  (acquisize) data from different devices and process , monitor this values and make some decission ( control ) according to this process values to ensure best operation of the plant beside that you can create some softwrer solution like alarms, events, trends and reporting.

SCADA is the monitoring system overall including the control system (PLC), the communication network and the HMI which is just part of the system which stands for Human Machine interface.

HMI in simple terms is an interface between the machine(Panel, switchgear, generator/motor, etc.) and its operator. HMI is part of SCADA system through which operator can monitor and control(If authorized) the respective machine.

SCADA as a whole is centralized control system consisting Single or Multiple HMI's with user defined control capabilities. Depending upon the need it may consist of station level or network level access.

SCADA is Software which can be controlled through Industrial PC, while HMI is also a software along with the hardware through which one can control the system from anywhere in the industry.

Human Machine Interface is simply the way by which humans interact with machines

SCADA- stands for "supervisory control and data acquisition" which is an integrated system that is used to control and monitor the workings of the individual parts of the plant 

 

The HMI (Human Machine Interface) is the front-end interface which is used by operators to interact with the supervisory system The SCADA (Supervisory control & Data Acquisition) - More similar to DCS (distributed geographically) but having some sort of operator interface to bring the data from various sections into a more sensible report

IN SIMPLE WORDS HMI(HUMAN MACHINE INTERFACE) IS HARDWARE AND SCADA IS SOFTWARE. BOTH HAVE THE SAME APPLICATION. HMI IS A DEVICE WHERE WE CAN GIVE THE GRAPHICAL FUNCTIONS AND OPERATIONS.SCADA IS A SOFTWARE WHICH SHOULD BE RUN IN A COMPUTER IN WHICH WE CAN GIVE GRAPHICAL FUNCTIONS AND OPERATIONS.IN LOW COST APPLICATIONS HMI IS USED BECAUSE SCADA SOFTWARE IS COSTLY