Using pH meter with ESP32

[tonntonn]

Hi!

I'm kind of a beginner in the field of analog sensors and I'm experiencing an issue that I don't really understand.

I am trying to use a pH-sensor from DFRobot (https://www.dfrobot.com/product-2069.html) to monitor my hydroponic system (together with other sensors I have installed using an ESP32), but I think I have a floating current somewhere in the system. This is because the value(with nothing at all connected to the connector on the protoboard) skyrockets from 0 to a lot depending on if I touch the protoboard or not. I will attach pictures of my (questionable) soldering job on the protoboard, and of the schematic. Is it appropriate to use a pull-down resistor on an analog sensor, and if it is, what value would be suitable?

For reference:

1. Humidity sensor connection
2. Water level sensor connection
3. Temperature sensor connection
4. pH sensor connection

Kind regards,
Antonia Fröjdh

[jim-p]

With nothing connected to an analog input, seeing crazy readings when you touch it is normal.
Your body is picking up all kinds of electrical fields and when you touch the pin you can impose a voltage.