Diagram is done in easyeda
Thanks, I'll have another look at that - I didnt find it easy though!
Regarding the AGND and DGND connections, how should it be done/improved?
I've done a simple diagram. You have not shown where the voltage being measured is coming from.
You need to ensure that parts that draw current (eg the arduino) dont affect the voltages due to track or connector resistance.
The best way to do this is
1: keep analog and digital grounds seperate and only connect at a "star point"
2: decouple with appropriate size (and type) capacitors.
In your case the ADC has seperate connections AGND and DGND
In the top fig all the currents flowing will disturb the voltage read by the ADC
In the bottom fig a capacitor supplies when needed some of the current to the changing load; and grounds are kept seperate to avoid this affecting the ADC reading.