A probe for measuring at least one parameter of a fluid flow in a pipe or duct , said probe comprising: a sensing device having a housing ; an inner tube arranged within the housing and having an open input end and an open output end for receiving a portion of the fluid flow; a space arranged between the tube and the housing ; a supporting structure adapted to mount the sensing device to an inside wall of the pipe or duct to be disposed in the fluid flow, the supporting structure comprising a bore therethrough communicating with the space ; and an array of at least three pressure sensors (18-21; 115-118; 180-186), each pressure sensor (18-21; 115-118; 180-186) spaced axially along the outer surface of the tube , and each pressure sensor (18-21; 115-118; 180-186) measuring an unsteady pressure and providing a measured pressure signal indicative of the unsteady pressure within the tube at the location of the respective pressure sensor (18-21; 115-118; 180-186), wherein the unsteady pressure propagates with the fluid flow; said probe further comprising a signal processor , which is responsive to the measured pressure signals, and configured for providing an output signal indicative of the at least one parameter of the fluid flowing through the pipe or duct . a sensing device having a housing ; an inner tube arranged within the housing and having an open input end and an open output end for receiving a portion of the fluid flow; a space arranged between the tube and the housing ; a supporting structure adapted to mount the sensing device to an inside wall of the pipe or duct to be disposed in the fluid flow, the supporting structure comprising a bore therethrough communicating with the space ; and an array of at least three pressure sensors (18-21; 115-118; 180-186), each pressure sensor (18-21; 115-118; 180-186) spaced axially along the outer surface of the tube , and each pressure sensor (18-21; 115-118; 180-186) measuring an unsteady pressure and providing a measured pressure signal indicative of the unsteady pressure within the tube at the location of the respective pressure sensor (18-21; 115-118; 180-186), wherein the unsteady pressure propagates with the fluid flow; a housing ; an inner tube arranged within the housing and having an open input end and an open output end for receiving a portion of the fluid flow; a space arranged between the tube and the housing ; a supporting structure adapted to mount the sensing device to an inside wall of the pipe or duct to be disposed in the fluid flow, the supporting structure comprising a bore therethrough communicating with the space ; and an array of at least three pressure sensors (18-21; 115-118; 180-186), each pressure sensor (18-21; 115-118; 180-186) spaced axially along the outer surface of the tube , and each pressure sensor (18-21; 115-118; 180-186) measuring an unsteady pressure and providing a measured pressure signal indicative of the unsteady pressure within the tube at the location of the respective pressure sensor (18-21; 115-118; 180-186), wherein the unsteady pressure propagates with the fluid flow; said probe further comprising a signal processor , which is responsive to the measured pressure signals, and configured for providing an output signal indicative of the at least one parameter of the fluid flowing through the pipe or duct . <EOS>