i have purchased a small board to measure pH with a MCU.
I am using a ADS1115 as ADC that have an internal Vref, that should be precise enough for my purpose.
Now, if i connect my Vin to the ADC pin, and read the Vin, i see that it fluctuate quite a bit from time to time.
I saved the V from pH board and the Vin to check if the Vin fluctuation affect the V from pH board since Vin it's used to power this board.
as expected, it was :(
So, what i can do to solve this issue? what's the most stable Vin that i can use? does a simple 7805 powered with 9V do the trick? there are other options to avoid this fluctuation?
Separate the Vin can make any sense? (separating Vin mean to use one to power the arduino & i2c things and the other to power the PH, of course ground will be in common)
Currently my Vin it's a usb power adapter, unbranded, no idea what's inside :)