An apparatus and a method are described for measuring water content and salt concentration in a multiphase fluid flow. A capacitive sensor (6, 7) is arranged in a pipe section (5) through which the multiphase fluid flow passes. A signal generator (10) is connected to the capacitive sensor (6, 7). A first measuring transducer (40) is adapted to measure a voltage across the capacitive sensor, and a second measuring transducer (50) is adapted to measure a current through the capacitive sensor. An output circuit (60) is adapted to generate output signals (70, 72) that indicate the salt concentration and water content in the multiphase fluid flow, based on signals emitted from the first (40) and the second (50) measuring transducer.