AC vs DC power supply

[Guest nschenk]

I'm in the beginning stages of a PLC project that is going to monitor a piece of HVAC equipment on a mobile piece of equipment. My question is which power supply will have better noise immunity - AC or DC? I'm thinking that a DC power supply would be better in this regard. I would appreciate any comments on the advantages/dissadvantages of either type of power supply. Thanks.

[KinK 0]

it depends on what you are doing ... if you just have on/off switches and controllers then I would say go for a low voltage ac its cheaper and works well in those types of applications. However if you are measuring analog signals then you will need to have a dc supply. I hope this helps if you need more info pls supply more info. Peace

[Guest nschenk]

Thanks, we will be using quite a few analog inputs to monitor pressure, temperature, and current.

[KinK 0]

then you pritty much have to go DC there I personaly havent ever come across any analog signals which run on AC.