Foundation H1 is intended primarily for process control, field-level interface and device integration. Running at 31.25 kbit/s, the technology interconnects devices such as transmitters and actuators on a field network. H1 is designed to operate on existing twisted pair instrument cabling with power and signal on the same wire. Fiber optic media is optional. It also supports Intrinsic Safety (IS) applications.
Foundation H1 devices comprise a function block application, act as a publisher and subscriber of process variables, transmit alarms and trends, and provide server functionality for host access and management functions. Devices can act as a scheduler and time master for regulating communication on a fieldbus segment. They are also used for bus interfaces in process control systems or in linking devices. Capable of controlling bus communications and many connections to multiple devices, they support both client and server applications.
H1 technology enables field instruments and other devices to execute control functions reducing the load on plant computers and workstations. Since the H1 network is digital, I/O conversion subsystems are eliminated. The Fieldbus Foundation tests and registers the devices to ensure interoperability of registered instruments from multiple vendors. This enables the end user to select the best instruments for the application regardless of the host system supplier.
Reports from leading adopters of the Foundation protocol demonstrate the advantages of control in the field with the H1 solution. For example, end users in the petrochemical industry have realized up to a 30 percent reduction in operating costs due to advanced diagnostics. Users have also seen that the all-digital H1 communications network is far less susceptible to electrical noise than traditional 4-20 mA analog systems.
H1 technology enjoys widespread acceptance throughout the process industries, and is included in the international IEC standard (IEC 61158).