Refractometer technology is based on the principle of refractive index of different liquid concentrations, which is an optical instrument with high accuracy and portability. calibration screw: drop distilled water on the , twist the adjustment screw, so the dividing line is adjusted to the scale 0%. Adjustable eyepiece: When the scale in the territory is not clear, you can gently rotate the eyepiece to adjust it. anti-corrosion and anti-rust, as new, beautiful . Anti-slip rubber cover feel soft, rotate lightly, not easy to slip off. Clear reading, fast detection, measurement, easy to . suitable for canned food, manufacturing, and fermentation, beverage, fruit, harvesting and other fields. Brix test range 0-90%, measurement accuracy: 0.1%. With temperature compensation function, to overcome the deviation of data caused by temperature changes, making the data more . Item Type: Refractometer : RHB-90ATC Sugar Test Range 0-90% Measurement Accuracy: 0.1% Automatic Temperature Compensation (): 10~30 (50~86) Package List: 1 x Refractometer 1 x Dropper 1 x Screwdriver 1 x Cloth(random colors, 't accept the specified color) Colour:As Shown Material:Metal Package Contents: 1 set x brix tester Only the above package content, other products are not included. Note: Light reflection and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.