I have connected my Arduino board with 12 v 1 A adaptor. When I measure the current with multimeter the 5v pin gives 8 v output.
Again I connected to 9v adapter the output is 6.3v. I think there is a problem with the voyage regulator. How can I get 5v output constantly.
Any ideas for this guy's pls help me I am in between a project.
Sounds like you have a bad regulator. You can replace it. Or use an offboard regulator and connect to 5V on the power header.
CrossRoads:
12V DC, or 12V AC?
You scared me in the moment!
But this can't be. The 12 AC adapter doesn't exist as a product, I think.
..Arnav
ArnavPawarAA:
The 12 AC adapter doesn't exist as a product, I think.
12V AC mains adapters exist. Think again.
thousiff:
I have connected my Arduino board with 12 v 1 A adaptor. When I measure the current with multimeter the 5v pin gives 8 v output.
Again I connected to 9v adapter the output is 6.3v. I think there is a problem with the voyage regulator. How can I get 5v output constantly.
Any ideas for this guy's pls help me I am in between a project.
What else is connected to your Uno?
To what did you connect it? Barrel, Vin?
TheMemberFormerlyKnownAsAWOL:
12V AC mains adapters exist. Think again.
Guess what happened if the OP had mistakenly connected 12 AC to the board? 
But I think that he didn't connect it, I think he bought the DC one and there is probably a problem with the Arduino power adapter.
.. Arnav