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

3-8
WORKING
ONLINE
Connecting to
a HART Loop
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.
A minimum of 250 ohms resistance must be present in
the HART loop for the 375 Field Communicator to
function properly.
For information about intrinsically safe connections, see
Appendix B.
NOTE
Dynamic variables shown while online represent the
digital data being sent from the device.
Three terminals for the lead set are on the top of the 375
Field Communicator. The lead set and terminals let you
connect the 375 Field Communicator to a device. 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