The HMI is an enclosed assembly that houses a human-machine interface terminal and the components an operator uses to run a machine. The HMI displays real-time data from the PLC and field devices, letting an operator start, stop, configure and monitor the process from one screen.
HMI terminal hardware inside the panel includes:
- A touchscreen or keypad HMI terminal, the operator’s window into the control system, mounted in the enclosure door for line-of-sight operation.
- A programmable logic controller (PLC), the controller the HMI reads from and writes to.
- Push-buttons, pilot lights and selector switches, the hard-wired controls UL 508A keeps as safety-critical functions.
- Power supply and terminal blocks, which condition and distribute control voltage to the HMI and field wiring.
If the screen fails mid-shift, then hard-wired pushbuttons let operators stop the machine. An HMI brings the operator interface, controller connection and hard-wired controls into one enclosed assembly for plant engineers to monitor. See how it fits the wider control panel design and build on our Components and Partners page.
