HYDROMETER- To Measure Sea Water Salinity Levels

[craigwb]

Hi All

Can someone please help me with the following:
I am in the process of building a Hydrometer to measure the changes in salinity levels of sea water. I am using Bronze probes due to there corrosive properties. I am using the ADC on the Pic 16F887 with Vref+ and the ADIN command. I get readings on the probes on large changes but, the slight changes in the Salinity levels I cannot seem to read, has anyone got some info on best way of doing this and reading it on the Pic? Should I amplify the signal before it goes to the Pic?

Kind Regards
Craig