What is salinity? What value should I enter in the SDR software?

Salinity is the dissolved salt content of water and is used especially when working with seawater samples.

A high salt content decreases the solubility of oxygen in water and thus the oxygen concentration (in mg/L, ppm or µmol/L). It has no influence on the oxygen partial pressure (oxygen units % air saturation, % oxygen, hPa, and Torr).

Seawater has an approx. salinity of 35 g / 1000 g, but this value can differ depending on the place the water was taken (e. g. dead sea, near rivers). If you work with samples other than seawater, you can estimate the salinity by calculating the g of salt per liter of your sample (e. g. if the medium composition is known).

! Please be aware that the salinity compensation is only valid for salinities up to 35 g / 1000 g and temperatures between 0 °C and 30 °C.

Leave the default value of 0, if:

  • the salinity of your sample does not lie within these limits
  • you don't know the salinity of your sample
  • you have chosen an oxygen partial pressure unit

! If you are doing a One-Point Adjustment in an oxygen concentration unit, please make sure to set the salinity value in the main window BEFORE you perform the adjustment. Otherwise, the calculated values will be wrong.


Select by industry

Presens TV

Watch tutorials, webinars and informative videos about PreSens optical sensor systems.

All videos