Hi,

What will change with the salinity level? Is it the OHM or the Capacitance or any other physical factor?

What level of accuraccy and resolution are you looking for? Maybe you can start by providing the formulas for how the theory behind salinity and the factor you wish to measure.

How much will oxidation of the probes influence the value?
How will the water level on the probes influence?
Does temperature affect the physical factors?

Interesting project but I am not sure you can find a simple answer here without giving alot more background information about the theories behind this.

But if I have a deep look into the crystal ball I would say that a 12-bit ADC could be worth looking into, the 887 pic only has 10-bit.