Some questions about EC meter

[moszeusz]

Hello, let me introduce myself. My name is Adam, I'm from Poland and I'm a chemist. I am planning to build a conductivity meter based on the Arduino shield design, in fact I am already at a quite advanced stage. Compared to the original design, I plan to change the power supply to 5V (and therefore use other op-amps), create a symmetrical power supply based on virtual ground (voltage divider + buffering op-amp), use a generator based on AD9833 and use an external ADC (ADS1115). The whole thing will be controlled using ESP32 instead of Arduino. I am wondering whether to add a second RMS (reference sin) converter in such a setup, because an external reference voltage cannot be supplied to the ADS1115. I also wonder what the purpose of adding this reference voltage in the second version of the conductivity meter is. Is it about increasing sensitivity? I'm sorry if the answer to this question is trivial, but I'm a beginner and not everything is clear to me. I also wanted to present some graphs for the results I obtained using the setup above (13 kHz, commercially available probe) (see attachments).

[Luc]

The idea of using a reference value was to compensate for small drifts in the amplitude of the applied sine wave.

I haven't test without it but when I designed the circuit I wanted to be safe and included as baseline.

[moszeusz]

Thanks, that was my second thought regarding this reference voltage