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D-2
Problem Possible Cause Possible Solution
No
communication
with field device
Insufficient loop resistance
at the HART frequencies.
Add an additional 250 ohm
resistor in series in the loop.
Place the HART Communicator
leads across the resistor and
verify if communication has
been restored.
Insufficientloop currentand
voltage at the field device
terminals.
Verify that there is at least 4mA
and 12V DC at the field device
terminals.
Field device may be set to
HART address other than
zero (multi-drop mode).
Change 275 mode to digital
polling.
Control systemis
communicating
HART, but the
275isnot
communicating
properly
HART communication with
the HART Communicator is
being prevented by the
control system
Stop HART communications on
the control system and verify if
communication between the
field devices and HART
Communicator is restored.
Battery pack
doesnotaccepta
charge
Battery pack has been
discharged past the normal
range.
Remove battery pack and
recharge while it is
disconnected from the
Communicator.
+24V DC
Power
250 ohm resistor
24V DC
Return
Field
Device
Control System field
Terminal blocks
0.1uF to
0.22uF
External
Capacitor
Shield terminal.
Floating at
transmitter end
250 ohm
external
loop resistor
Control
System Side
Field
Device side
Fielddevicemust
have 4mA and 12V
DC at terminals
Explosions can result in death or
serious injury. Do not exceed the
allowed loop capacitance.
WARNING
!