A human-machine interface (HMI) device is the primary tool by which the operator can read and control the main parameters of the system or installation. The parameters and current status presented on the HMI display are grouped on individual screens, corresponding to functions controlled by the PLC unit.

The HMI device can be integrated with the system frame, in the system operator position, or it can be mounted in the electronic rack, inside or as an additional, large touchscreen on a rotary arm.