Orion Instruments Eclipse 705 - Manual (Page 37)

37 57-600 Eclipse ® Guided Wave Radar Transmitter
2.8 F OUNDATION fieldbus ™ Digital Communications
2.8.1 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 ECLIPSE
Model 705FF transmitter is a F
OUNDATION
fieldbus regis-
tered device that communicates with the H1 Foundation
Fieldbus protocol operating at 31.25 kbits/sec. The H1
physical layer is an approved IEC 61158 standard. The
figure on page 38 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.
2.7.4 HART Revision Table
Model 705
HART Version HCF Release Date Compatible with 705 Software
Dev V1 DD V1 July 1998 Version 1.2B and earlier
Dev V1 DD V2 November 1998 Version 1.2C through 1.3D
Dev V3 DD V1 April 1999 Version 1.4A through 1.4C
Dev V4 DD V1 October 1999 Version 1.5 and later
Model 705 2.x
HART Version HCF Release Date Compatible with 705 Software
Dev V1 DD V1 June 2000 Version 2.0A through 2.2C
Dev V2 DD V1 September 2001 Version 2.3A through 2.3E
Dev V3 DD V1 September 2003 Version 2.4A through 2.4B
Dev V4 DD V1 April 2004 Version 2.5A and later
Model 705 3.x
HART Version HCF Release Date Compatible with 705 Software
Dev V1 DD V2 September 2008 Version 3.0A and later
Dev V2 DD V1 August 2011 Version 3.2A and later