PLC-HMI Interfaces

Programmable Logic Controllers (PLCs) are small computers that control interface/operator (I/O) positions to make sure every component of a computer controlled system work together in harmony. Human Machine Interfaces (HMI) is the configuration software that will allow an individual to enter the PLC memory location for the input that is tied to a specific operation (e.g., a valve open limit switch). That memory location can also be tied to a text message that says, “Valve Open”. These systems allow the operation of complex systems from a single location, and provide feedback on the operation. Graphics that illustrates the process are often incorporated into a screen display.


The key to a successful PLC-HMI fueling system design is understanding every detail of the operation, including consequences of wrong actions. WPI’s engineers have this knowledge, as well as the design expertise to resolve issues such as how the HMI will communicate to the PLC, how the PC based configuration package will communicate with the O/I, etc.