SCADA: Human Machine Interface (HMI)

What Is HMI

Human operators control the process. It is through the HMI apparatus that the human operators receive the processed data to control the process.

Why HMI

A need was felt for standardizing a way for control and monitor of many remote controllers including control devices like PLC. This need in essence gave rise to HMI industry. Automatic pre-programmed control over a process is provided by a PLC. However it is hard to gather data manually from them because of their usual distribution across a plant. There was never any standardized way that PLC could present information to an operator. PLC and other controllers provide the SCADA system with the information through some form of network. In SCADA this information is combined and formatted. Linking an HMI to a database serves various purposes. Such database apart from giving diagnostic and trend-indicating data also provides management information like procedures for schedule maintenance, sensor or machine specific detailed schematics and logistic information. Troubleshooting guides and expertise are also provided to the system.

HMI Packages

An integrated HMI/SCADA System uses protocols for communication that are open and non-proprietary. Now almost for a decade, majority of the PLC manufacturers have been offering this kind of integrated HMI/SCADA System. A large number of specialized and third party HMI packages are now available in the market. In such packages, there are in-built compatibilities with most of the major PLCs. This facilitates the technicians and electrical or mechanical engineers to configure HMI by themselves and without the necessity for a customized program developed by a software engineer. The HMI/SCADA package because of its dependability and compatibility has become very popular. It finds wide use ranging from small applications like temperature control in a room to such large applications as controlling the process in a nuclear power plant. It is one of the best ways to control and monitor remotely located data with large geographic distribution.