Filter
Top Products
Reference Manual
00809-0100-4021, Rev DA
November 2004
Rosemount 3144P
3-24
HART
MULTIDROP
COMMUNICATION
Multidropping refers to the connection of several transmitters to a single
communications transmission line. Communication between the host and the
transmitters takes place digitally with the analog output of the transmitters
deactivated. Many of Rosemount transmitters can be multidropped. With the
HART communications protocol, up to 15 transmitters can be connected on a
single twisted pair of wires or over leased phone lines.
The application 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. Each transmitter is identified by a
unique address (1–15) and responds to the commands defined in the HART
protocol.
Figure 3-4. Typical Multidropped
Network
Figure 3-4 shows a typical multidrop network. Do not use this figure as an
installation diagram. Contact Emerson Process Management product support
with specific requirements for multidrop applications.
A HART-based communicator can test, configure, and format a multidropped
3144P transmitter the same as in a standard point-to-point installation.
NOTE
The 3144P is set to address 0 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 address must be changed to a
number between 1 and 15. This change deactivates the 4–20 mA analog
output, sending it to 4 mA. The failure mode current also is disabled.
AMS
Right click and select “Configuration Properties” from the menu screen.
Select the “HART” tab. From here, assign the polling address.
Power Supply
Power Supply
Impedance
Handheld Terminal
Computer or DCS
3144P HART
transmitter
4–20 mA
HART Interface
250 Ω