Model 8712C/U/H Magnetic Flowmeter Transmitters
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MULTIDROP
COMMUNICATIONS
Multidrop configuration refers to the connection of several transmitters
to a single communications transmission line. Communication between
the HART Communicator and the transmitters takes place digitally
with the analog output of the transmitters deactivated. Using the
HART communications protocol, up to 15 transmitters can be connected
on a single twisted pair of wires or over 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
communication protocol.
Figure 4-2 shows a typical multidrop network. This figure is not an
installation diagram. Contact Rosemount product support with specific
requirements for multidrop applications.
The HART Communicator can test, configure, and format a
Model 8712C/U/H multidrop installation the same way as it can
a Model 8712C/U/H in a standard point-to-point installation.
FIGURE 4-2. Typical Multidrop Network
RS-232-C
Bell 202
Modem
4–20 mA
Power
Supply
3051-0087A, 8712-8712B01B
Model 8712C/U/H Magnetic Flowmeter Transmitters
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