Bringamosa:
Now i did it anyways. This works for me. 12v battery powering my arduino, measuring the same 12v battery. Or you can measure voltage of something else.
Bringamosa, thanks. I think that in previous post kind users explained to me that the problem wasn't to measure the same voltage, but the impediance of the input. I understand that input must have sufficient impedance otherwise it will drop the sensor voltage down.
standard multimeter impedience is enought, since I have always read the sensor in that way.