pH-meter connection to analog input

Other Hardware Sensors
1

Hello.

Once again silly questions (maybe), it´s been a while without crafting anything...

I´m getting some -20 to +20 millivolts from a self powering probe here. I´d like to bring those millivolts in Arduinos analog input.

There was an earlier conversation on negative voltages in analog input here but i cant continue that thread anymore.

The probe itself acts like an power source via electrolytic reaction. If plunged into base material it gives negative voltage, then neutral stuff no voltage (meters needle stays in middlescale) and acid gives positive voltage.

These voltages i´d like to introduce into my Mega´s analog input, and those readouts i would like to get airborne maybe via bt or wlan.

Is the information i need in the old thread or should i take a different approach because of the self powering properties of the probe?

Thanks in advance for thoughts on this one.

I.A.
Finland

2

You cannot measure negative voltages using Arduino, and you will also need some amplification to measure a few millivolts with any accuracy.

You can solve both problems at once using an op amp. For many possibilities, google "gain and offset op amp circuit".

One such design guide.

3

Thanks a lot, i´ll study this!

br

I.A.