I want to measure a DC voltage with very high resolution (uV) and send the value to a PLC (based on an Arduino Mega.) Initially I selected an ADS1115, but I got some power noise due to loop currents (discussion in this question). I decided to replace this ADC by another of higher resolution (ADS1219) but I got similar noise as before. I think that the reason could be that both analog/digital grounds are connected on the ADS1219 evaluation board (explained in this question).
As a visual reference, find the following image of possible ADS1219 breakboard (found in here) which does not separate the grounds:
To avoid the evaluation board, I am designing a new board with an ADS1219 where I will separate the grounds. These are my questions:
- How do I connect each ground to the rest of the circuit? My idea is to separate both analog and digital parts and include a new connector to have both AGND and DGND, like this image modified by myself but based on the reference circuit mentioned above:
- Do the analog and digital ground/paths need special design at PCB level? That is, do they need separated ground planes? Do the traces need to be special, or it is just normal connections as AVDD and DVDD?
- Does it make sense to have a digital isolator for the I2C communication? As commented in here it helped a lot with the ADS1115, but I am not sure if it makes sense for the ADS1219 if I separate the grounds.