The RHS series are designed for testing the concentration of salt water and brine in an aquarium enviroment or wider scale uses. The unit provides a direct reading of the specific gravity and salinity concentration (Parts Per Thousand) of salt in water. It provides reliable refractive index and salinity readings of total dissolved solids of aqueous solutions. It is used for quality control in research and clinical laboratories. The Salinity Refractometer is also used in oceanography and seawater studies. The model having ATC (Automatic Temperature Compensation) is ideal for field use.