Redox reading erratic

[almost]

how do the readings change? range? frequency?
do the readings also change if the probe is immerged in glas of water?

It changes +-5 in a second.
I didn't test it in a glass of water, I can try if needed.
The probe is that of Aquamedic because it has o 13mm thread and it was calibrated in your fluids, calibration went well.

The same probe in another ORP controller, gives very stable readings.

I have one of your ORP probes, waiting to connect it to the expansion box.

Tell me what you want me to try.