I'm building a 24-bit ADC board for Arduino that can sense microvolts (biological signals). What are some good techniques to lower the noise that will negatively affect the ADC resolution?
What I've done already:
- made a 4 layer board, with internal ground plane and digital power plane
- added separate analog and digital power supplies
- kept high-frequency digital signals away from the input lines, and also from the ADC except where they enter the ADC
- most ground connections go to the ground plane using vias
- there is one single ground for both analog and digital ICs
- RC filtering on the input signals
Are there other techniques that would be more effective? Are any of the ones I used counterproductive?