A combined by-pass valve and pressure sensor comprising a housing, a fluid inlet whereby fluid can enter the housing, a fluid outlet whereby fluid can exit the housing, a valve seat between said inlet and said outlet, a valve closure member movable relative to the housing along a first axis between a closed position in which the valve closure member engages said seat to prevent communication between said fluid inlet and said fluid outlet, and an open position in which said valve closure member is displaced from said seat placing said fluid inlet in communication with said fluid outlet through said housing, resilient means urging said valve closure member to said closed position, a pressure element within said housing having a first surface thereof exposed to the pressure conditions at said fluid inlet, and a second, opposite surface thereof, exposed to pressure conditions at said fluid outlet, said element being movable, in the direction of said axis, between a rest position to which it is resiliently urged, and a displaced position in which it engages an abutment of said valve closure member, and, a position transducer for providing a signal indicative of the position of pressure element.