Human machine interface (HMI) software enables operators to manage industrial and process control machinery via a computer-based graphical user interface (GUI). The computer on which HMI software is installed is called a human machine interface or HMI. There are two basic types of HMI: supervisory level and machine level. Supervisory level HMI is designed for control room environments and used for system control and data acquisition (SCADA), a process control application which collects data from sensors on the shop floor and sends the information to a central computer for processing. Machine level HMI uses embedded, machine-level devices within the production facility itself. Most human machine interface (HMI) software is designed for either supervisory level HMI or machine level HMI; however, applications that are suitable for both types of HMI are also available. These software applications are more expensive, but can eliminate redundancies and reduce long-term costs.
Selecting human machine interface (HMI) software requires an analysis of product specifications and features. Important considerations include system architectures, standards and platforms; ease of implementation, administration, and use; performance, scalability, and integration; and total costs and pricing. Some human machine interface (HMI) software provides data logging, alarms, security, forecasting, operations planning and control (OPC), and ActiveX technologies. Others support data migration from legacy systems. Communication on multiple networks can support up to four channels. Supported networks include ControlNet and DeviceNet. ControlNet is a real-time, control-layer network that provides high-speed transport of both time-critical I/O data and messaging data. DeviceNet is designed to connect industrial devices such as limit switches, photoelectric cells, valve manifolds, motor starters, drives, and operator displays to programmable logic controllers (PLC) and personal computers (PC).
Some human machine interface (HMI) software runs on Microsoft Windows CE, a version of the Windows operating system that is designed for handheld devices. Microsoft and Windows are registered trademarks of Microsoft Corp. Windows CE allows users to deploy the same human machine interface (HMI) software on distributed HMI servers, machine-level embedded HMI, diskless open-HMI machines, and portable or pocket-sized HMI devices.