The ph sensor itself is connected to the 5V pin of the esp32 (actually outputs about 4.8V), but I wrote it with 3.3/4096. As a result, the pH of tap water was about 6.81, but is this a correct result? When I tried running it with 4.8/4096, the pH of tap water was about 9.97.

Thank you for your reply.  I'll try it and see if it works.

Thank you for your reply.Since the analog input value of the probe terminal source is originally a large value, I do not know if this method will improve it well, but I will try it.