Dear Pepito Payet

These links might be an valuable asset, have a look:

1. https://forum.arduino.cc/t/how-to-read-a-negative-voltage/16652

2. https://forum.arduino.cc/t/analog-input-positive-negative-voltage/571026

3. https://www.quora.com/Can-I-give-negative-voltage-to-analog-pin-of-Arduino-without-destroying-it

4. https://electronics.stackexchange.com/questions/108320/read-positive-and-negative-voltage-in-arduino

Kind Regards

Qamar Ul Islam

Dear Pepito Payet,

I suggest you to see links on subject.

https://www.instructables.com/Voltage-Measurement-Using-Arduino/

https://www.youtube.com/watch?v=LSBpb18zcp0

https://electronoobs.com/eng_arduino_tut83.php

Article Voltmeter Design Based on ADS1115 and Arduino Uno for DC Res...

Best regards

Dear Pepito Payet,

I agree with Mohamed-Mourad Lafifi.

Hi Pepito,

I suggest you search for Inverter Amplifier.

An inverting amplifier circuit will invert the voltage polarity (- -> +) and at the same time will allow you to amplify the voltage (in the range of 0-5V for Arduino) and increase the sensitivity of the readings.

A voltage follower between your sensor and the inverting amplifier can increase the stability of readings.

I have a tutorial about op amps in Portuguese:

http://www.c2o.pro.br/hackaguas/apc.html

But you can see the translation on Google:

https://tinyurl.com/nnjmawcw

Best Regards,

Markos

Qamar Ul Islam Thanks for your reply.

Mohamed-Mourad Lafifi Thanks for your reply.

Bashar Hamad Thanks for your reply.

Markos Brazilo Thanks for your reply.