The Extech RF20 Portable Salinity Refractometer measures the concentration of salt with automatic temperature concentration. RF20: Portable Salinity Refractometer (0 to 100ppt) with ATC Measures the concentration of dissolved salt in fluids Features: Compact size, easy to operate Automatic Temperature Compensation (ATC) from 10 to 30°C Provides accurate and repeatable measurements on easy to read scale Requires only 2 or 3 drops of solution The prism and lens with a simple focus adjustment Complete with case, calibration screwdriver, plastic pipette and calibration solution Specifications: Type: Salt (ATC) Range: 0 to 100ppt (10 to 30C), 1.000 to 1.070 Refractive Index Resolution: 1ppt, 0.001 Accuracy: +/-0.1%, +/-0.001 Dimensions: 7.6"x1.5"x1.5" (194x38x38mm) Weight: 8oz (227g) Extech RF18 Salt Meter à¤Ã×èͧÇÑ´¤ÇÒÁà¤çÁ Ẻ¡ÅéͧÊèͧ