Rockwell Automation 1769-IF4FXOF2F Compact Combination Fast Analog I/O Module - Manual (Page 43)

Publication 1769-UM019A-EN-P - October 2008 43
Module Data, Status, and Channel Configuration Chapter 3
Enable/Disable Channel (EC)
This configuration selection lets each channel be enabled individually.
Input Filter Selection
The input filter selection field lets you select the filter frequency for
each channel. The filter frequency affects the noise rejection
characteristics, channel step response, and module update time, as
explained below.
Noise Rejection
The module uses firmware that provides noise rejection for the input
signals. The filter is programmable, allowing you to select from nine
filter frequencies for each channel. A lower frequency (60 Hz versus
1000 Hz) can provide better noise rejection but it increases channel
step-response time.
Normal Mode Rejection is better than 50 dB at 50 and 60 Hz, with the
50 and 60 Hz filters selected, respectively. Transducer power-supply
noise, transducer circuit noise, or process variable irregularities may
also be sources of normal mode noise.
Common Mode Rejection is better than 70 dB at 50 and 60 Hz, with
the 50 and 60 Hz filters selected, respectively. The modules perform
well in the presence of common mode noise as long as the signals
applied to the IN+ and ANLG Com input terminals do not exceed the
working voltage rating of the module. Improper earth ground may be
a source of common mode noise.
TIP
When a channel is not enabled (EC = 0), no voltage or current
reading is provided to the controller by the A/D converter.
Any analog input channel that is not wired to a voltage or
current source should not be enabled in the module
configuration file. Enabling unused analog inputs can result in
non-zero values being displayed in the module input-data file.
Either disable all unused analog inputs or place a jumper wire
between the Vin+ and V/Iin- terminals for those channels.