Issue
A voltage between 50mV and 500mV at 50Hz is measured at the Digital Input and has raised concern as to it's affect on the Input.
Environment
b4, i2, b3, xP Modules, IOU modules. (anything with a Digital Input)
Cause
Concern over effect of induced voltage on the Digital Inputs.
Resolution
There is an RC filter on those inputs that should protect it at 50Hz for that voltage. The filter will protect down to 15Hz and the Digital Input will not turn on before 1.6V. Although this should not be a problem, and the RC filter should effectively cut this off before it hits the input circuitry, 500mV is still a substantial noise signal on an input and may be indicative of a grounding problem. It would be wise to try to eliminate this induced voltage.