These devices or programs are vital for smooth machine or process operation.
HMI – Human Machine Interface
HMIs are the computer displays that an operator uses to interface with the process or machine. They send and receive tag data to/from the controller via a built-in driver or an OPC server such as Kepware. Sometimes, a touchscreen is preferable. Other times, a desktop PC is fine.
HMIs can provide control and monitoring of equipment, alarms, diagnostics, etc. An example would be the Rockwell FactoryTalk View ME (Machine Edition) or the Siemens WinCC Basic.
SCADA – Supervisory Control and Data Acquisition
SCADA combines an HMI with any combination of the following:
- Multiple HMIs
- Server/client architecture
- Server contains all the graphics, communicates to equipment, and serves it up to clients
- Client looks to server for updated graphics and data.
- Data Historians and historical trends
- Reporting § Batch operation
- Networks including Ethernet, Fiber optic, field bus
- Server Redundancy
Examples include the Rockwell FactoryTalk View SE (Site Edition), and the ICONICS Genesis64. SCADA shares a lot of functionality available with a DCS (Distributed Control System), such as Siemens PCS7.