Oceanographers can measure the salinity of a body of water in several ways, but the two most common methods are using a hydrometer set or a salinometer.
A hydrometer set consists of a cylinder, a hydrometer, a thermometer, and a temperature-salinity-density (or TSD) graph. The hydrometer measures the water density as higher salt content means denser water, which causes the hydrometer to float higher in the cylinder. The temperature is then measured and both are compared to a plot of the density and temperature readings on the TSD graph. This then gives them the salinity, as temperature, salinity, and density are related variables.
Oceanographers can also use a salinometer to determine salinity by measuring electrical conductivity, but the instrument is not very accurate. Both of these tools measure salinity in parts per thousand.
