3 of 9 sensors "saturating"

[lhimo88]

Hi there! I managed to connect and plot the signal from 9 of these sensors. They seem to work fine, except for the last three of them which are kind of saturating. In the screen attached you can see the spikes when I dip the working sensors in water, the central one seems to be not functioning for some reason, and the last three which indicate a constant value. What can it be?

[WiFive]

[ESP_Sprite]

I assume these are connected through the ADC of the ESP32? To which pins specifically? How did you set the gain in the ADC? If you connect a multimeter to the output of the sensors, what's the output of the good and the offending sensor? Have you tried exchanging the good and a wrong sensor and seeing if the graph moves along?

[lhimo88]

The working pins I'm using are GPIO 32,33,34,35,36 and 39. Therefore I'm missing other 3 pins, I tried GPIO 25,26,27 and GPIO 0,2,4 with the saturating behaviour.

[lhimo88]

P.s. I'm reading analog values with:

Code: Select all

#define ANALOG_PIN_8 2
int analog_value_8 = 0;
  analog_value_8 = analogRead(ANALOG_PIN_8);