i mean : the input was 5volt DC, from an ATX power supply (confirmed by measuring with a multimeter).
the Scope was set to 5volt/div, DC, 1X100Hz/div.
the reading was a line, 3division higher that it was originaly.
Note: the picture i posted before was just to show you the calibration pot.
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i have another picture:
i was measuring the main AC from my wall.
![](http://i192.photobucket.com/albums/z24/hitachi8/wallhot.jpg)
as you can see, the scope is adjusted to 100V/div (AC).
the input was 123~AC, but the scope read 400VAC.