Foundation Fieldbus H1 level has been designed as a digital replacement of the 4 to 20mA standard in the process industries. Foundation Fieldbus is also a LAN (Local Area Network) for instruments used in both process and manufacturing automation with built-in capability to distribute the control application across the network. The physical wiring is also fully compatible with intrinsic safety (IS) or nonincendive wiring standards and may be used in hazardous, as well as general purpose areas. In hazardous areas standard explosion-proofing or power limited concepts may be used, as well as IS concepts, offering greater cabling design flexibility.

Foundation Fieldbus (FF) Features

• Reduce field wiring costs.

• Intrinsic safety wiring option available to further reduce costs in hazardous environments.

• Same bus used for analog and discrete devices.

• Control (LAS) for the segment may reside in the field devices freeing up space in central controllers.

• Time stamping of control parameters performed in field devices and coupled to control data to optimize operating performance.

• Provides greater controllability and process information.

• Standardized function blocks, representing control and I/O; speed set up.

• Long bus length of 1900m (6,175 ft) and spurs up to 120m (390 ft) span most process systems.
  Supported by over 80% of the world’s process instrumentation suppliers.

Foundation Fieldbus Economic Analysis
When using a StoneL VCT module and integrating it into the Foundation Fieldbus (FF) network illustrated, there are significant savings. This system consists of 16 automated valve systems located in a cluster approximately 200 feet from the I/O rack. Each of the automated valves is located 20 feet apart in the cluster. Following is an estimated comparison:


Foundation Fieldbus Analog Point Addition to StoneL I/O Modules
The StoneL Foundation Fieldbus I/O modules have an auxiliary 4 to 20mA input and a 4 to 20mA output which is powered from the supplemental 24VDC supply bus. Additional savings may result from connecting the 4 to 20mA device directly to the StoneL I/O instead of running wires back to I/O at the controller. The additional analog input would be represented as an AI (Analog Input) function block as part of the StoneL device description. StoneL I/O analog 4 to 20mA point addition is illustrated.

The 4 to 20mA instrument may be conveniently wired directly into the StoneL I/O module. With a conventional system the control would need a 200 foot run back to the controller. Other savings would result from:

• Reduction in design time because of simpler conduit and cabling systems.

• Reduction in conduit and cabinetry space.

• Right first time wiring and easier troubleshooting.

• Faster commissioning.
   

Foundation Fieldbus Network Specifications