The BTX-1 handheld refractometer with automatic temperature compensation. It is simple to operate and will provide you with quick and accurate concentration measurements of nearly any solution. The ATC feature frees the user from recalibrating when used in environments with large temperature swings. Automatic Temperature Compensation Largest & Sharpest Display Available Exclusive "Zero Ring" Requires No Calibration Tools Durable, All Metal Design Operation consists of placing a drop of the sample on the prism, closing the daylight plate, then looking through the focusable cushioned rubber eyepiece for reading. Tool - Free Calibration - Place a few drops of distilled water on the prism turn the Zero Ring until the shadow line is at the correct value and lock the set screw. Specifications Range : 0 to 32 degrees Resolution: 0.2 ATC: 10 to 30 C Accuracy: +/- 0.2 Dimensions: 40 x 40 x 165 mm Durable rugged construction backed by a 1 Year WarrantySupplied with storage case, transfer pipet and instruction manual