As said The other term used to describe a diode is rectifier
Diodes don't produce DC.Diodes rectify the AC to be in one direction
Capacictors due to charging and discharging Cycles convert this time variant signal(Review the AC defination:Variable in both the intensity and direction)to approximate dc
c level with ripples)
As long as we increase the capacitance we reduce the ripple may be we reachch a pure DC.
ready961
As you said using diodes is to prevent the two sensors to feedback each other.
Juad
Sfety is an important issue .input modules is more expensive than adding relays.how much does it cost the relays and the wiring and the space compared to the input module and in the same time how much does it cost your name with the client if your plc damged due to that you don't want to spend a more small amount of money ,and how much you will gain from providing a good quality and durable work.Think about it.
ready961
think about what will happen if one diode damage due to any spike?What will happen?
How you will install the diodes in your panel?
how the maintenance man will know id the diode damaged?
I hope that this will help
BR