This paper presents a study on the calibration of conductivity sensors. The puropse is to demonstrate the effect of the salinity concentration on the response of conductivity sensor. Several experiments are performed on three sensors of different technologies: a Seabird Sbe37-SIP MicroCAT, a Falmouth Scientific Inc. IMCTD-MBP-D and a NKE Instrumentation Smatch. The analysis of the results shows an overall impact of the salinity level on the sensor response. This effect is discussed regarding the oceanographic requirements.