High voltage Sensor

I’m hoping there is a way to read high voltage ( 400 -600 VAC 3 Phase) for the FEZ Spider. Any help would be greatly appreciated.

Sorry, I should have been more clear. I am wanting to monitor the voltage on a system with no load so that I can prevent a machine from starting with uneven or low voltage.

There are many ways but 400V has its risks. Best way would be to use a drop down transformer. You can cheat with resistors but with ground issues and the risk I say this is a no go!

Welcome to the community.

If just looking for a low voltage point, you should consider using optos. you can have the opto trigger on a certain voltage point. This way your board is isolated from the mains

Thanks, would appreciate a link for optos.