I am a newbie with electronics,there is a circuit attached of a voltage transformer AC-AC step downing 230 v to 6v, there is an input of 2.5 v on the secondary to add up the voltage (6V), besides scaling up the voltage whats other main purpose of that reference voltage there, what if we dont add it what will happen?
The A/D can only accept voltages between ground and supply.
In order to keep the AC voltage from going negative (below ground), one transformer terminal is connected to a fixed mid-voltage. Now AC can swing positive (2.5 to 5volt) and negative (2.5 to 0volt).
I believe that you are talking about a current transformer ?
if you do not elevate your zero to allow it to create a sine wave with 2.5 volts as the center, then you will only have one half of the reading. half of the time it will be out of range, below 0v. This will result in missing half the data. [ edit to correct and add more information ]
if you are trying to measure voltage, you can add a bridge rectifier (4 diodes) to create a DC voltage.
for current, you need to use the 2.5v offset.
for voltage, you need to change to DC
have you read the articles at openenergymonitor.org ?