Emerson Rosemount 8600D Series Reference Manual page 65

Reference Manual
00809-0100-4860, Rev BC
Pulse output test
Field Comm.
Pulse Output Test is a fixed frequency mode test that checks the integrity of the pulse loop. It
tests that all connections are good and that pulse output is running on the loop.
HART output
Field Comm.
Multidrop configuration refers to the connection of several flowmeters to a single
communications transmission line. Communication occurs digitally between a HART-based
communicator or control system and the flowmeters. Multidrop mode automatically
deactivates the analog output of the flowmeters. Using the HART communications protocol, up
to 15 transmitters can be connected on a single twisted pair of wires or over leased phone lines.
The use of a multidrop installation requires consideration of the update rate necessary from
each transmitter, the combination of transmitter models, and the length of the transmission
line. Multidrop installations are not recommended where intrinsic safety is a requirement.
Communication with the transmitters can be accomplished with commercially available Bell
202 modems and a host implementing the HART protocol. Each transmitter is identified by a
unique address (1-15) and responds to the commands defined in the HART protocol.
Figure 4-1
diagram. Contact Rosemount product support with specific requirements for multidrop
applications.
Figure 4-1. Typical Multidrop Network
Note
The Rosemount 8600D is set to poll address zero at the factory, allowing it to operate in the
standard point-to-point manner with a 4–20 mA output signal. To activate multidrop
communication, the transmitter poll address must be changed to a number between 1 and 15.
This change deactivates the 4–20 mA analog output, setting it to 4 mA, and disables the failure
mode alarm signal.
Operation
1, 4, 2, 2, 2
1, 4, 2, 3
shows a typical multidrop network. This figure is not intended as an installation
RS-232-C
Bell 202
Modem
Power
Supply
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Section 4: Operation
January 2013
57