Too little salt in brine can risk Bacterial issues, too much could affect the quality and texture of your olives. That is why measuring the salt levels is so important.
The salinity meter measures salt levels in brine solution.
Refractometers are precision optical instruments which work using
the principle of light refraction through liquids. When
passing through a liquid the refracted angle will be shown on the
scale determining the amount of dissolved solids in the liquid.
How to Calibrate a Refractometer