hello, im interested if there is any way how to measure ac voltage - its about -2V to 2V ..
i dont need any minus values, but the main problem is, when I use diode, I will loose some voltage .. so it is not a precise measuring .. any idea? any IC to do that or to convert from ac to dc without loosing anything?
thanks
Most of the time you build in the compensation for the diode. Otherwise use a "true RMS" converter chip.
There are lots to choose from but here is one
Two resistors to create 2.5V for the Arduino analog input and a capacitor to the signal could do.
What frequency is the signal ?
Where does is come from ?
Is the ground of the signal connected to the Arduino ?
To measure the mains voltage (using a transformer) the Arduino samples the signal and calculates the true RMS value.
http://coolarduino.wordpress.com/2013/01/09/audio-vu-meter/
Probably, you won't need log conversion at step 5, just multiply with calibration coefficient