Abstract: A device for sensing and monitoring the pressure variations of a pressurized fluid in a duct (13), comprises an upper body (1) coupled to a pressurized air source (5) and a lower body (2) which is coupled by means of a resilient ring, to a sleeve (12) welded to the duct (13) in which the pressure is to be monitored. A graduated scale duct (18), associated with the upper body and communicating with a needle valve (16) affords the possibility of visually monitoring the adjusted air amount. A coupling duct (19) communicates with a joining duct (20), to which a pressure detecting instrument (22) is applied and leads to an interspace (23) defined between the lower and upper bodies and communicates in turn with the inner side of a diaphragm (26) which, on the opposite side, contacts the pressurized fluid.