Instruments used to measure the specific gravity or relative density of liquid samples.

Each element has a unique density, which can be used to identify it. Density measurement is used to monitor the quality of products and processes.

Density meters do not measure specific gravity directly, but it is inferred and calculated based on other measurements. Specific gravity or relative density is the sample density compared to a reference substance.

Digital density meters often use oscillation tube technology for rapid measurements. The sample is injected into a U-shaped glass tube, which is then oscillated. The resulting frequency is measured and used to calculate the density.

Some advantages of digital over manual measurements include:

• Requires smaller sample volumes (less than 2 mL)
• Rapid results (less than 60 seconds)
• Accuracy (readability to 0.00002 g/cm³)
• GLP compliance
• Automation and high throughput

Benchtop digital density meters may also have built-in Peltier thermostats for better temperature control. They are typically used to measure density, specific gravity, alcohol, sugars, and API gravity.

Handheld density meters offer portable measurements of density, specific gravity, ethanol (alcohol), Brix, API gravity Baumé, H₂SO₄, Plato, Proof (US and IP), and other user-defined concentrations. They also include a thermometer for automatic temperature compensation.

Density meters may be used for:

• Incoming goods and materials inspections
• Final product quality control assessments
• Measuring concentrations
• Purity checks
• Alcohol measurements

Density meters are also used in varied applications to measure liquids, slurries, and sludges flowing through pipelines and in mining, dredging, wastewater treatment, paper, oil, and gas industries.