HART Functionality
3-10
Figure 3-3 illustrates how to connect the 375 Field
Communicator directly to the terminals of a HART
device.
Figure 3-3. Connecting Directly to a HART Device
Figure 3-4 illustrates how to connect the optional 250
ohm resistor. Attaching a resistor is necessary if less
than 250 ohms resistance is present in the HART loop.
Figure 3-4. Connecting with a 250 Ohm Resistor
To temporarily install the optional 250 ohm load resistor:
1. Insert the load resistor into the lead set jacks.
2. Open the loop to allow connection of the resistor in
series in the loop.
3. Close the loop using the lead set connectors.
Current
meter
mA
Power
supply
RL≥250Ω
HART compatible
device
+
-
+
-
+
-+
-
+
-
+-
Optional
250-Ohm Load
Resistor
HART compatible
device
Power
Supply
–
+
–
+
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