Usage: This refractometer allows you to determine the ethylene glycol and propylene glycol concentration for frost protection in your car, solar installations, heat pumps, cooling systems, heating systems, or other machinery and water systems. Measurement Range: Ethanediol (ethylene glycol): 0 to -50°C; Propanediol (propylene glycol): 0 to -50°C; Windshield cleaning fluid - ethanol + water: 0°C to -40°C; Propylene glycol + water (SRF1): 0°C to -40°C; AdBlue: urea concentration 30% - 35%; Acid battery: 1.10 to 1.40 kg/L. Precision Measurement: Features an optical system with 4-8x magnification and stepless manual focus, suitable for all users and compatible with both nearsighted and farsighted vision. It is recommended to view measurements without glasses. Calibration: Perform zero calibration using distilled water at 20°C. Includes automatic temperature compensation. Note: Due to manual measurement and display differences, slight variations between individual products and images may occur.