Please help me identify this noise on my ADC
Proto-boards are hardware platforms quite sensitive to noise. Note that it is build with a lot of metalic rails inside. In addition the aerial wirings just catch extra EMI from air. You could at least minimise the noise amplitude by grounding the surrounding non used rails of the proto-board, as well as shielding the wire with brings the signal to the board, along with spreading ceramic capacitors at power rails close to the AD.