What does a hydrometer measure?

A hydrometer is an instrument specifically designed to measure the specific gravity of liquids. Specific gravity is the ratio of the density of a substance to the density of a reference substance, typically water for liquids. This measurement is crucial in various applications, including determining the concentration of solutions in HVAC systems, where refrigerants or other fluids are often involved.

The design of a hydrometer typically features a calibrated scale on a floating stem. When placed in a liquid, the hydrometer sinks to a level that corresponds with the specific gravity, allowing users to read the value directly from the scale. This capability is particularly useful for HVAC technicians when assessing the condition and concentration of refrigerants or other fluids in residential air conditioning systems.

Temperature, pressure, and flow rate are measured using different types of instruments such as thermometers, pressure gauges, and flow meters, respectively. Therefore, the focus on specific gravity underscores the unique purpose of a hydrometer in the field.