A. Ethylene glycol: -50°C - 0°C (concentration 0 - 70%); Propylene glycol: -50°C - 0°C (concentration 0 - 70%); Resolution coefficient: 5°C, 5% (automatic temperature compensation); Temperature compensation range: 10°C - 30°C. B. Field of view: Middle scale: (Ethylene glycol) Freezing point of ethylene glycol - type antifreeze; (Propylene glycol) Freezing point of propylene glycol - type antifreeze. Left scale: (Battery fluid) Specific gravity of battery fluid: 1.15 - 1.20 Needs charging; 1.20 - 1.25 Sufficient power; 1.25 - 1.30 Ample power. Right scale: Freezing point of glass cleaning fluid. C. Working principle: This instrument can measure the freezing points of antifreeze and glass cleaner, and the specific gravity of lead - acid battery electrolyte. It is equipped with a temperature compensation device to ensure relatively simple and convenient measurement and relatively accurate measurement at an ambient temperature of 10°C - 30°C. Its basic principle is to measure the refractive index of the solution using the total reflection critical angle method, and then calibrate the concentration and performance of the measured liquid. Due to its relatively reliable principle and relatively accurate measurement, it can meet practical needs. It also has the characteristics of small size, light weight, beautiful appearance, and convenient use, so it is widely used in the automotive industry. D. Usage precautions: (1) Avoid placing the instrument in an environment with a relative humidity exceeding 85% for a long time to prevent affecting the optical system. (2) Prevent liquids and water from entering the adjustment knob and the eyepiece to prevent damaging the internal components. (3) Avoid subjecting it to severe vibration and collision to prevent damaging the instrument's accuracy. (4) After use, wipe the prism and the refraction plate clean with a clean cloth. E. List of accessories: (1) 1 refractometer; (2) 1 pipette; (3) 1 instruction manual; (4) 1 mini - screwdriver; (5) 1 cleaning cloth.