Rockwell Automation T80004 Application Note Field Loop Configuration - Manual (Page 31)

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AN-T80004 Field Loop Configuration
Issue 10 Jun 13 AN-T80004 31
It is advised to add load resistors to loads under about 20 to 25mA to increase them above the
minimum threshold. It is also possible to apply a threshold of 3mA to a group, but only if the group has
entirely light loads; this setting will otherwise clearly increase the chances of noise causing a false
positive diagnosis, causing a potential shutdown.
Quad Structure Modules 8472, 8473
These modules do not have the triplicated output circuit described above. Instead, they have a quad
arrangement of switches. The no-load threshold applies to the entire load current, so a threshold of
20mA allows a minimum load of 20mA. The default is 10mA on older 8472s and 20mA on newer
8472s and on 8473s, as shown in the specifications in the product descriptions.