Rockwell Automation 1756-OF8H ControlLogix HART Analog I/O Modules User Manual
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Rockwell Automation Publication 1756-UM533C-EN-P - February 2011
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1756-IF16H HART Analog Input Module Chapter 5
The 1756-IF16H is a differential input module. However there are limitations on
its use in differential mode. Any time the low ends of the terminal block pins are
connected together they must also be jumpered to the RTN pin on the terminal
block. There are two scenarios in which this happens.
First, if a single power supply is used for multiple devices then the low end from
each channel is connected together and connected to the ground return of the
power supply. See the following diagram.
Figure 13 - Single Power Supply with Multiple HART Devices
The second way for channels to share a ground is to have multiple power supplies
hooked to the same ground. In this case the low ends of the channels are
effectively connected together by the common grounds of the power supplies.
Figure 14 - Multiple Power Supplies with a Common Ground
Power Supply 1
HART Device 1
HART Device 2
+
-
+
-
RTN
Because the low end of the
terminal block pins are
connected together, they must
also be connected to RTN.
45120
IN00+
IN00-
IN01+
IN01-
Ground wire from AC
source common to both
DC power supplies
Power Supply 1
Power Supply 2
The low end of the terminal block pins are
hooked together via the common ground of the
power supples and must be connected to the
RTN pin.
HART Device 1
HART Device 2
+
-
+
-
RTN
Jumper low end to
RTN on terminal block
45119
IN00+
IN00-
IN01+
IN01-