Publication 1769-UM002B-EN-P - July 2005
Installation and Wiring 2-11
System Wiring Guidelines
Consider the following when wiring your system:
General
• All module commons (ANLG COM) are connected in the analog
module. The analog common (ANLG 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)
1769-IF4 and -IF8 Input Modules
• If multiple power supplies are used with analog inputs, the power supply
commons must be connected together.
• The 1769-IF4 and -IF8 modules do not provide loop power for analog
inputs. Use a power supply that matches the input transmitter
specifications.
• Differential analog inputs are more immune to noise than single-ended
analog inputs.
• Voltages on Vin+, V/Iin-, and Iin+ of the 1769-IF4 and -IF8 modules
must be within ±10V dc of analog common.
1769-OF2, -OF8C, and -OF8V Output Modules
• Voltage outputs (Vout 0+ and Vout 1+ for 1769-OF2, Vout 0+
through Vout 7+ for 1769-OF8V) of the output modules are referenced
to ANLG COM. Load resistance for a voltage output channel must be
equal to or greater than 1K Ω.
• Current outputs (Iout 0+ and Iout 1+ for 1769-OF2, Iout 0+ through
Iout 7+ for 1769-OF8C) of the output modules source current that
returns to ANLG COM. Load resistance for a current output channel
must remain between 0 and 500 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.
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