The Thermosalinograph (TSG) measures temperature and conductivity, which is then used to calculate salinity. With the salinity from the TSG, and the temperature from the remote temperature probe, it can also calculate sound velocity at the sea surface. The remote temperature probe is located in the bow thruster room, whereas the TSG sensor is located in the lower wet lab, and both sensors have seawater continuously pumped through them to measure these variables from the sea surface.
Here is a breakdown of the variables plotted below:
- External Temperature (C) – water temp just after it enters the hull
- Internal Temperature (C) – water temp just before it enters the TSG sensor
- Conductivity (S/m) – The degree to which the water entering the TSG sensor conducts electricity. If Temperature is measured at the sensor, Conductivity can be used to find Salinity.
- Salinity (unitless) – Calculated from Conductivity as the amount of dissolved matter in seawater. The range of salinity of the global ocean is 31 – 38.
- Sound Velocity (m/s) – The velocity of sound through the water column. The speed of sound in water is approximately 1500 m/s. Sound velocity is used for precise mapping measurements of the seafloor.