Magnetrol 2xx Specifications download pdf (Page 21)

46-648 Jupiter Magnetostrictive Transmitters

1.8 FOUNDATION Fieldbus Digital Communications

1.8.1 Description

FOUNDATION 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

Terminator

Power

Conditioner

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 39 40

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Magnetrol 2xx Specifications Page 21