Fangrui Product Details Digital Refractometer With 0- Range, 0. Accuracy And 0. Resolution. An Innovative Substitute For Traditional Birx Meter To Measure The Sugar Content. Automatic Temperature Compensation (10c To 40c) And High Light-transmission Prism For Higher Accuracy And Consistance. Easy To Use, Do Zero Calibration For The First Use. Then Drop Samples, Close The Cover And Start Button, The Value Be Displayed On The Screen. High Definition Digital Meter With Fast Reading. The Digital Meter Is Equiped With 600mah Built-in Lithium Battery. One Full Charge Lasts At Least One Month. Usb Charge, Eco-friendly . The Sample Tank Part Is Waterproof And Can Be Washed Under Running Water After Use. Please Keep The Charging Port Away From Water. The Refractometer Is A Good Assistant For , Winemakers, Food Beverage Producers, Fruit Growers And Sellers. Attention!!! 1.test Water Is 0. Before Using(0. Accuracy),if Not ,need Zero Clearing Or Calibration. 2.sample Quantity:1/2 Of The Depth Of The Sampling Tank At Lea