To enable easy alignment of a leakage outlet according to known guidelines, a connecting device (1) for connecting a sensor (3) to a unit (2) containing a fluid is provided, comprising a first mounting portion (1a) to which the sensor (3) is mountable, a second mounting portion (1b) which is mountable to the unit (2), a central portion (1c) located between the first and second mounting portions (1a and 1b) and a leakage ring (1e) covering the bore (1d) of the central portion (1c), the leakage ring (1e) being sealed and rotatable relative to the central portion (1c), wherein the leakage ring (1e) has a leakage outlet (1f) on its periphery, the leakage outlet (1f) being provided to be located in the region of a lowest position of the periphery of the leakage ring (1e) in an operating position to allow any fluid present to drain.