Ok if i understand, currently my current Ipd1 is to weak, because in the figure 2, we can see the linearity of K3 range from about 5uA to 50uA. And to have the best linearity, we need to have 50uA for 60mV no ?
I will try say with the gain of 10 this monday. Maybe it's fine, and i after i will say you if it works or not.
I use a Lm324 for the OPA, I have forget to says taht maybe the Voltage drop by the is too big, in this case, i will use a supply of 6V.
Thanks you again for your time