Conductivity Calibration: Results of an Interlaboratory Comparison

The international thermodynamic equation of seawater or TEOS-10, gives several definitions for the concept of salinity, but recommends that the salinity reported in national data bases remains the Practical Salinity. Practical Salinity is obtained traditionally by measuring the electrical conductivity of seawater using appropriately-designed conductivity cells incorporated into submersible probes and other similar instruments or instrument packages. Such cells are usually calibrated to allow salinity to be measured in the $2-42$ range of the Practical salinity Scale of 1978. The MINKE project has been the framework for an interlaboratory comparison of the calibration of a SBE 37 CTD probe at different salinities. The goal was to test the validity of a calibration made with a seawater of salinity 35 when the probe is used in seawater of a different salinity. This paper presents the results of this interlaboratory comparison.