Refractometer

Measuring coolant concentrations is essential to cooling system maintenance. This tool measures concentration of coolant mixture in engine. Place small sample of coolant on lens, then hold lens up to light source. Light bends through liquid, providing an accurate reading on scale.
Most technicians use hydrometers to test coolant concentration via gravity or floating ball scales
Hydrometers must be temperature corrected and may give false readings when testing new, propylene-based coolants
Automatically corrects for temperature on both types of coolant (ethylene and propylene glycol) while measuring battery charge levels