I need to capture the waveform of a low-amplitude signal that sits on top of a slow-varying, higher-amplitude component. I'm thinking of using an ADC with two channels, and feed one of them with a low-pass filtered version of the signal and the other one with an amplified, high-pass filtered version of the signal. That would increase the apparent resolution of my ADC. Am I wrong? Can you foresee any problems with this?
I forgot to say I have to capture the low-frequency component as well (the algorithm needs the average value of the signal).
The "high"-frequency component goes from 0.01 hertz to 10 hertz. The low-frequency component is mainly the average value of the signal, but it may change, slowly. The faster-changing component may have an amplitude 100 times smaller than the maximum average value. The microcontroller we will use has a 12-bit ADC (I cannot change that), but with many channels.