[quote=”David” post=3149][…] manage to have very low pH around 2.72- 3 with conductivity like 12 to 20 µS/cm.[/quote]Never ever, I’m sorry! It’ not possible to gain very low conductivity at very low pH, this would violate some electrochemical laws. I think your analyzers went wrong.
Try to measure the output of an cation exchanger; its pH will be very low, about 2.7 or lower, depending on the used tapwaters cation concentration, and its EC will skyrocket to 500 µS/cm and much more. This is because the acid ions H3O+ have their part in conductivity, the higher the concentration, the higher the conductivity.
I measured different humins in an oversaturated concentration and compared the data to a pure H3O+-curve which is caculable from electrochemical laws (named DHO here, blue curve).
A probe, which differs from the pure curve, contributes to conductivity in addition.