Working Online; Connecting To A Hart Loop - Emerson 375 User Manual

3-8
WORKING
ONLINE
Connecting to
a HART loop
The Online menu displays data for the HART device to
which you are connected. The 375 Field Communicator
can communicate with a transmitter from the control
room, the instrument site, or any wiring termination point
in the loop.
Connect the 375 Field Communicator with the
appropriate connectors in parallel with the instrument or
load resistor. The HART connections are not polarity
sensitive.
In order for the 375 Field Communicator to function
properly, a minimum of 250 ohms resistance must be
present in the HART loop.
For information about intrinsically safe connections, see
Appendix B.
NOTE
Dynamic variables shown while online represent the
digital data being sent from the device.
There are three terminals on the top of the 375 Field
Communicator. Two are red and one is black. Each red
terminal is a positive connection for its protocol. The
black terminal is a common terminal shared by both
protocols. An access door ensures only one pair of
terminals is exposed at any one time; see Figure 3-1.
Several markings indicate which pair of terminals is for
which protocol.
HART Functionality