# Density meter

A density meter, also known as a densimeter, is a device that measures the density. Density is usually abbreviated as either ${\displaystyle \rho }$ or ${\displaystyle D}$. Typically, density either has the units of ${\displaystyle kg/m^{3}}$ or ${\displaystyle lb/ft^{3}}$. The most basic principle of how density is calculated is by the formula:

${\displaystyle \rho ={\frac {m}{V}}}$

Where:

${\displaystyle \rho }$ = the density of the sample.
${\displaystyle m}$ = the mass of the sample.
${\displaystyle V}$ = the volume of the sample.

Many density meters can measure both the wet portion and the dry portion of a sample. The wet portion comprises the density from all liquids present in the sample. The dry solids comprise solely of the density of the solids present in the sample.

A density meter does not measure the specific gravity of a sample directly. However, the specific gravity can be inferred from a density meter. The specific gravity is defined as the density of a sample compared to the density of a reference. The reference density is typically of that of water. The specific gravity is found by the following equation:

${\displaystyle SG_{s}={\frac {\rho _{s}}{\rho _{r}}}}$

Where:

${\displaystyle SG_{s}}$ = the specific gravity of the sample.
${\displaystyle \rho _{s}}$ = the density of the sample that needs to be measured.
${\displaystyle \rho _{r}}$ = the density of the reference material (usually water).

Density meters come in many varieties. Different types include: nuclear, coriolis, ultrasound, microwave, and gravitic. Each type measures the density differently. Each type has its advantages and drawbacks.

Density meters have many applications in various parts of various industries. Density meters are used to measure slurries, sludges, and other liquids that flow through the pipeline. Industries such as mining, dredging, wastewater treatment, paper, oil, and gas all have uses for density meters at various points during their respective processes.