A sensor device for use in a medical fluid delivery system or an infusion pump device comprises a fluidic chamber (1) with a deformable cover (2) closing at least one area of the chamber and an optical detection system comprising at least one light emitter (3) for emitting one or more incident light beams (4) and a sensor unit (5) for monitoring one or more reflected light beams (6). In a pressurized state of the fluidic chamber (1) the deformable cover (2) is deformed such that it forms an inflexion point area (12) within the deformed cover (2). The one or more incident light beams (6) emitted by the light emitter (3) are directed on the cover (2) such that the one or more incident light beams (4) are reflected essentially in the inflexion point area (12).
