Foundation Fieldbus H1

Infobox Fieldbus Protocol
Name = Foundation Fieldbus H1
Type_of_Network = Process Control
Physical_Media = Twisted Pair, fiber
Network_Topology = Star, Bus
Maximum_Devices = 32 nodes/segment
Maximum_Distance = 9500 meters with 4 repeaters(depending on minimum signal strength and power to reach the field devices)
Device_Addressing = Automatic when connected to segment
Governing_Body = Fieldbus Foundation
URL = [http://www.fieldbus.org www.fieldbus.org]

Description

Foundation Fieldbus H1 is one of the Foundation Fieldbus protocol versions. It utilises either twisted pair, or fiber media to communicate between multiple nodes (devices) and the controller. The controller requires only one communication point to communicate with up to 32 nodes, this is a drastic improvement over the standard 4-20mA communication method which required a separate communication point for each communication device on the controller system.

The Foundation Fieldbus H1 has support for Intrinsically Safe Wiring with 4-6 devices per repeated segment depending on power requirements and other parameters.

The original concept was to connect as many as can be in forming a node,but limited by signal strength.

There is another level of bus called H2 bus.which is host communications level.

Parameters

The communication line can stretch 1900 meters without repeaters or 9500 meters with up to 4 allowed repeaters.

Communication Methods

The communication methods supported are:
* Client/Server
* Publisher/Subscriber
* Event
* Scheduled/Unscheduled

Use

This protocol is primarily used for analog and discrete process control devices.the primary advantage is configuration by functional block concept.

Power Supply

The big advantage of Foundation Fieldbus is that it allows power to be transferred over the communication bus to the controlled devices, this requires a Foundation Fieldbus power supply.

Termination

The communication bus in for this protocol requires two terminators one near each end of the bus.so that there is no signal reflections.

Development

This protocol was developed and is supported by Fieldbus Foundation

References

[http://www.fieldbus.org/ http://www.fieldbus.org/]

[http://www.topworx.com/networx/ff.html http://www.topworx.com/networx/ff.html]