Series 302 FIELDBUS FOUNDATION – Installation, Operation and Maintenance Manual
1.2
The
Series 302
devices are protected against reverse polarity, and can withstand up to 35 VDC
without damage.
The Figure 1.3 show as to connect a device in a fieldbus network.
Figure 1.3 – Connecting a device to the Fieldbus network
Foundation Fieldbus Physical Medium, Cabling and Installation
The standard first versions specify two options for the physical layer: H1 and H2. The H1, with rate
of 31.25 Kbits/s is oriented basically to field device (transmitters, valve positioners, etc), and it can
be used in areas requiring intrinsic safety (explosive atmospheres). The H2, with rate from 1 to 2.5
Mbps, would be used to integrate controllers and more complex devices.
Due to the fast technological evolution, the H2 was substituted by the HSE that uses Ethernet at 100
Mbps. Therefore, for field devices connection there is the FOUNDATION fieldbus H1, with physical
layer based on ISAS50.02-1992 or IEC61158-2:2000. For connection among PLCs, Linking
Devices, Gateways and PCs, there is the FOUNDATION fieldbus HSE, based on Ethernet
(IEEE802.3-2000, ISO/IEC8802.3-2000).
Foundation Fieldbus H1 Network
A Fieldbus network is composed by several H1 buses, connected to each other by bridges or
Foundation Fieldbus Linking Devices that connect the H1 networks to the HSE backbone.
According to definitions, each H1bus can hold, theoretically, up to 32 devices not powered by the
bus. In practice, there may be up to 12 field devices powered by the bus and other 20 devices not
powered by the bus, each one with a single logical address in the network (1 Byte). This limit is due
mainly to the electric characteristics of the power supply and the current consumption of the devices.
In practical terms, it is recommended that the total number of devices doesn't surpass 10, because
the network traffic tends to become very high and there may be performance degradation. In
classified areas, it is recommended to analyze the output of the intrinsic safety barrier to define the
number of devices. With the FISCO concept, there may be a larger amount of devices per segment.
The wiring length can reach 1900 m, and up to 4 repeaters can be used.
Figure 1.4 –Simplicity of the Foundation Fieldbus H1 Physical Layer (IEC61158-2)
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