Orion Instruments Jupiter 2xx - Manual (Page 21)

46-648 Jupiter Magnetostrictive Transmitters 21
1.8 F OUNDATION Fieldbus Digital Communications
1.8.1 Description
F OUNDATION Fieldbus ™ is a digital communications system
that serially interconnects devices in the field. A Fieldbus
system is similar to a Distributed Control System (DCS)
with two exceptions:
• Although a Fieldbus system can use the same physical
wiring as an existing 4–20 mA device, Fieldbus devices are
not connected point-to-point, but rather are multidropped
on a single pair of wires (referred to as a segment).
• Fieldbus is a system that allows the user to distribute
control across a network. Fieldbus devices are smart and
actually maintain control over the system.
Unlike 4–20 mA analog installations in which the two
wires carry a single variable (the varying 4–20 mA current),
a digital communications scheme such as Fieldbus considers
the two wires as a network. The network can carry many
process variables as well as other information. The Jupiter
transmitter is a F
OUNDATION Fieldbus ™ registered device
that communicates with the H1 Foundation Fieldbus pro-
tocol operating at 31.25 kbits/sec. The H1 physical layer is
an approved IEC 61158 standard. The illustration below
shows a typical Fieldbus installation.
An IEC61158 shielded twisted pair wire segment can be as
long as 6234 feet (1900 meters) without a repeater. Up to
4 repeaters per segment can be used to extend the distance.
The maximum number of devices allowed on a Fieldbus
segment is 32 although this depends on the current draw
of the devices on any given segment.
Typical Fieldbus Installation
Control Room
Power Supply
Terminator
6234 feet (1900 meters) maximum
PC
Terminator
Power
Conditioner