Measurement Range and Minimum Scale: Sugar: 0–40%, Minimum Scale: 0.2 Alcohol Content: 0–25% Temperature Compensation Function: Compensates for temperature-induced data deviation to ensure higher measurement accuracy. Improved Eyepiece: Features heavy crown optical glass lens (not standard glass) for enhanced clarity and reduced observer eye fatigue. Usage Instructions: 1) Point the refracting prism toward light; adjust the eyepiece focusing ring until the reference line appears sharp and clear. 2) Calibration: Before measurement, prepare calibration liquid (distilled water); ensure both instrument and sample are at the same temperature. Lift the cover plate, place 1–2 drops of calibration liquid on the refracting prism, gently close the cover to form a distinct light/dark boundary line. Adjust the calibration screw so that this boundary aligns precisely with the 0% reference line in the eyepiece field of view. Note: This optical instrument is factory-calibrated and ready for immediate use. 3) Lift the cover plate, wipe the prism surface with a soft cloth, apply 1–2 drops of the test solution onto the refracting prism, gently close the cover, and read the concentration and density value indicated by the light/dark boundary line on the scale. 4) After measurement, wipe the prism surface and cover plate with a damp soft cloth, dry thoroughly, and store the instrument properly. Calibration: Zero-point calibration is required before each measurement. Place a few drops of distilled water on the detection prism, adjust the zero-setting screw until the boundary line aligns with the 0% mark on the scale. Wipe the prism clean and proceed with testing. Some models require a standard solution instead of distilled water for calibration. Precautions: This is a precision optical instrument—observe the following during use and maintenance: 1) Handle with care; strictly follow instructions; do not loosen connecting parts arbitrarily; avoid dropping, impact, or strong vibration. 2) Do not immerse the instrument directly in water after use; clean optical surfaces only with a soft, clean cloth—avoid scratches or damage. 3) Store in a dry, non-corrosive environment. 4) Prevent loss of small detachable parts. Applications: Refractometers offer advantages including simple robust construction, ease of use and portability, clear optical view, and cost-effectiveness. Sugar-series refractometers are used in food preservation, fruit juice production, brewing and fermentation, beverage manufacturing, fruit processing, honey harvesting, and related fields. Salt-series refractometers are used in marine aquaculture, aquarium management, and physiological saline preparation. Medical-series refractometers are used for serum protein detection and urine specific gravity testing. Industrial-series refractometers are used for testing automotive battery fluids, refrigerants, cleaning solutions, machine tool lubricants, and cutting fluids.