Xbee ADC value

I am trying to connect a current sensor clamp to a xbee ADC IO.

The problem is that the clamp give me values on a sinusoidal form from 0V to 1V. And I need to sample from time to time (30 sec) the peek value of the signal. (to multiply for the constat and get the current value)

So I tried to use the rectifier circuit with a capacitor and a resistor in parallel, but the 0.7Vf of the diode does not let me measure the inferior values, and i cannot apply because the ADC has a reference of 1.2V.

So I searched for a better way to do it add I found the precision wave rectifier: http://upload.wikimedia.org/wikipedia/commons/c/ca/Op-Amp_Precision_Rectifier_%28Improved%29.svg

So I did a simulation with Qucs and it worked like a charm. So I assembled the circuit in a test board and wen i connect it to the xbee and read it on the computer it gives me values even when i dont have a current passing on the clamp.

I checked with the oscilloscope and when o i connect the rectifier circuit to the ADC the voltage raises from 0 to a 0.04V.

Can any one help me I do not understand why it raises when i connect it to a ADC input.

That's a split-rail circuit - the negative supply needs to be below the input/output level (by at least s diode-forward-drop if the op-amp is rail-to-rail, by more if it isn't.)