All the ships of the French Oceanographic Fleet are fitted with SeaBird SBE21 sensors on a dedicated seawater system supplied by a centrifugal pump. The sensor is mounted in a water jacket and provides temperature and conductivity data in real time. Another temperature sensor, such as an SBE38 (digital) or an SBE3S (analogue), is mounted near the system’s seawater inlet in order to correct temperature inaccuracies caused by the piping warming the water.

The thermosalinograph comprises a cell fitted with electrodes which determine the conductivity of seawater. Thermistors measure water temperature in the cell and near the hull.

The sensors are calibrated every year.


  • Range: 0–70 mmho/cm
  • Accuracy: ±0.01 mmho/cm
  • Resolution: ±0.0o1 mmho/cm


  • Range: -5 to +35 °C
  • Accuracy: ±0.01 °C
  • Resolution: ±0.001 °C
  • Sample interval: 5 seconds or more by increments of 1 second
  • Recommended flow rate: 1 litre per second