Rockwell Automation 1769-IF16V Compact High Density Analog Input Modules - Manual (Page 21)

Publication 1769-UM018A-EN-P - October 2008 21
Installation and Wiring Chapter 2
System Wiring Guidelines Consider the following when wiring your system:
•
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.
•
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.
•
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)
Keep shield
connection to ground as short as possible.
•
If multiple power supplies are used with analog inputs, the
power supply commons must be connected.
•
The modules do not provide loop power for analog inputs. Use
a Class 2 power supply that matches the input transmitter
specifications.
•
Voltages on IN+ terminals of the modules must be within
±10V DC of module common (COM).
Effect of Transducer/Sensor and Cable Length Impedance on
Voltage Input Accuracy
For voltage inputs, the length of the cable used between the
transducer/sensor and the module can affect the accuracy of the data
provided by the module.
(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.