Human machine interface (HMI), also sometimes referred to as the operator interface (OI) is a means for the operator to monitor and control machinery and processes.
Although initially designed as a replacement for pushbuttons, in the 1980s operator interface matured into a more compact, manageable and flexible way for plant personnel to interact with plant processes.
They have evolved into much more than simple monitoring and can include, for example, web serving, email, trending and smartphone support.
Hardware, also referred to as the OI, is the online unit or operator station that displays insight into the machine functionality. OI hardware includes:
PC-based software is used to configure and transfer applications to and from the OI. OI software includes:
Dual-scan LCD color screens are currently more affordable, but have a somewhat limited viewing angle and are less luminous.
Active-matrix thin-film transistor (TFT) color screens are quire bright and easily viewable with a broad viewing angle (from the side).
Proprietary design features both hardware and software that is unique to the brand or HMI. The software will only run on the designed hardware, and hardware will only run the software package.
Proprietary units typically have an advantage of lower pricing because they are designed for a dedicated OI.
Open platform design features unique software, which typically runs on a Windows-based personal computer platform.
Open designs are typically based on an Intel architecture PC, which allows for use of off-the-shelf hardware and software to extend the capabilities of the OI. Today's open systems are typically more expensive than proprietary designs.
Eaton's HMIs range in screen size from 3.5 inches up to 22 inches of
The use of an HMI benefits the user in many ways including: