I have a low frequency (50Hz) signal which can be positive or negative (centered around system ground) depending on the mode selected. The signal has a maximum amplitude of +/- 12V. So, just to be clear, when one mode is selected, the signal is positive from 0 to 12V and when the other mode is selected, the signal is negative from 0 to -12V.
Now, I would like to digitize this signal using a 12bit ADC (MCP3208 - datasheet) and it's fine (preferable perhaps) if the signal is rectified so that it is always positive.
So, I have two main choices: I can rectify and scale my signal, which will give me more digital precision or I can DC bias and scale the signal with the obvious loss of digital precision (converting 0-12V, as opposed to converting 0-24V). Option #1 would seem the obvious choice, but my concern is with the precision rectifier circuit.
The question then is: which option will distort the signal the least and (in essence) how precise are precision rectifier circuits when compared to a simple buffered voltage divider?
I should add that in this application maintaining the shape of the signal is important, more important than resolution, I think.