How It Works – Specific Gravity Hydrometer

A specific gravity hydrometer is a precision instrument used to measure the density of a liquid, based on Archimedes’ principle. It operates on the condition that an object floating in a liquid is in equilibrium when the weight of the object equals the weight of the liquid it displaces.

The hydrometer consists of a sealed glass tube with uniform wall thickness, featuring a calibrated scale printed on the inner wall. The scale is more widely spaced at the top and denser at the bottom, allowing for accurate and easy reading.

The lower end is slightly enlarged into a weighted bulb containing fine lead shot, which enables the hydrometer to:

• immerse vertically in the tested liquid,

• float steadily at the correct depth,

• and automatically return to an upright vertical position after being disturbed.

When the hydrometer floats in a liquid, its own weight equals the weight of the displaced liquid. Different liquids cause the hydrometer to sink to different depths, and this variation is directly translated into density values on the calibrated scale.

⭐ Key Advantages

✔ Accurate and reliable liquid density measurement
✔ Based on proven physical principles (Archimedes’ law)
✔ Direct reading with no calculations required
✔ Excellent stability thanks to weighted bulb design
✔ Durable calibrated glass construction

A trusted and essential instrument for laboratory analysis, quality control, fuel testing, and professional density measurements.