Rockwell Automation 1790D-NOV2/TNOV2 CompactBlock LDX Analog Modules - Manual (Page 24)

Publication 1790-UM001A-EN-P - March 2002
2-8 Installation and Wiring
I/O System
Wiring Guidelines Consider the following when wiring your system:
General
•
All module commons (COM) are connected in the analog
module. The analog common (COM) is not connected to earth
ground inside the module.
•
Channels are not isolated from each other.
•
Do not use the analog module’s NC terminals as connection
points.
•
To ensure optimum accuracy, limit overall cable impedance by
keeping your cable as short as possible. Locate the I/O system
as close to your sensors or actuators as your application will
permit.
•
Use Belden™ 8761, or equivalent, shielded wire.
•
Keep shield connection to ground as short as possible.
•
Under normal conditions, the drain wire and shield junction
must be connected to earth ground via a panel or DIN rail
mounting screw at the analog I/O module end.
(1)
Input Modules
•
If multiple power supplies are used with analog inputs, the
power supply commons must be connected together.
•
The module does not provide loop power for analog inputs. Use
a power supply that matches the input transmitter specifications.
Output Modules
•
Voltage outputs (CH0 and CH1) of the 1790D-NOV2/TNOV2
modules are referenced to COM. Load resistance for a voltage
output channel must be equal to or greater than 1K
Ω
.
•
Current outputs (CH0 and CH1) of the 1790D-NOC2/TNOC2
modules source current that returns to COM. Load resistance for
a current output channel must remain between 0 and 600
Ω
.
(1)
In environments where high-frequency noise may be present, it may be necessary to directly ground cable
shields to earth at the module end and via a 0.1µF capacitor at the sensor end.