Usage: This refractometer measures the ethylene glycol and propylene glycol concentration for frost protection in your car, solar installation, heat pumps, freezing point devices, heating systems, or other machines or water installations. MEASUREMENT RANGE: Ethanediol (ethylene glycol): 0 to -50°C; Propanediol (propylene glycol): 0 to -50°C; Windscreen 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 from 1.10 to 1.40 kg/L. Precision measurement: The optical system of the eyepiece group features a 4-8 times amplification system with stepless manual focus. It can fit all eyes. For best results, do not wear glasses when observing measured data. Calibration: Zero calibration using distilled water at 20°C, automatic temperature compensation. Please note that due to manual measurements and display differences, there may be slight variations between individual products and photos.