The invention relates to a water sensor for detecting water in gas oil filters, comprising a first and a second electrode (1.1, 1.2); a first and a second earth connection (3.1, 3.2) for earthing the first electrode (1.1) and the second electrode (1.2); a first switch (4.1) arranged in the first earth connection (3.1); a second switch (4.2) arranged in the second earth connection (3.2); a first and a second current connection (2.1, 2.2) for injecting a first current into the first electrode (1.1) and a second current into the second electrode (1.2); and a current-generating circuit (5) connected to the first electrode (1.1) and to the second electrode (1.2) by means of the first current connection (2.1) and the second current connection (2.2) respectively, and designed to inject the first current into the first electrode (1.1) and the second current into the second electrode (1.2), the first current and the second current being the same.
