Multidrop Communication - Omega PX2088 User Manual

4. Check the current meter installed in the test loop to verify that it reads the
value you commanded the transmitter to output. If the readings do not match,
the transmitter requires an output trim or the current meter is
malfunctioning.
After completing the test procedure, the display returns to the loop test screen and
allows you to choose another output value.

MULTIDROP COMMUNICATION

Multidropping transmitters 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 the SMART transmitters can be Multidropped.
With the HART smart communications protocol, up to 15 transmitters
can be connected on a single twisted pair of wires or over leased phone lines. Note
that Burst Mode Operation is not compatible with multidrop communications.
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. 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 2-4 shows a typical multidrop network. This figure is not intended as an
installation diagram.
FIGURE 2-4. Typical Multidrop Network.
RS-232-C
HART-based communicators can test, configure, and format a multidropped
transmitter the same way as a transmitter in a standard point-to-point installation.
Bell 202
Modem
Power
2-13