A wind turbine blade having a leading edge and a trailing edge, a blade root, a blade tip, a blade axis pointing from blade root to blade tip, and having a pressure-side skin and a suction-side skin, the suction-side skin joining at the leading edge and trailing edge with the pressure-side skin to form a hollow blade structure, the wind turbine blade comprising a pressure measuring unit, the pressure measuring unit comprising: a first connection tube and a first sensing port, the first sensing port fixedly attached to one of the suction-side skin and the pressure-side skin, and having a first through-hole connecting the exterior of the blade to the first connection tube, a second connection tube and a second sensing port, the second sensing port fixedly attached to one of the suction-side skin and the pressure-side skin, and having a second through-hole connecting the exterior of the blade to the second connection tube, a pressure-sensing unit receiving the first connection tube at a first inlet port and receiving the second connection tube at a second inlet port, the pressure-sensing unit further having: a first resistive unit in fluid communication with the first inlet port, and a second resistive unit in fluid communication with the second inlet port, the first resistive unit and the second resistive unit also in fluid communication with ambient air at a preselected point so as to allow fluid passage of ambient air into the first and second connection tubes (161, 165), respectively, with a pre-determined amount of fluid resistance, and a differential pressure sensor producing a differential-pressure signal indicative of the pressure differential across the first inlet port and the second inlet port. a first connection tube and a first sensing port, the first sensing port fixedly attached to one of the suction-side skin and the pressure-side skin, and having a first through-hole connecting the exterior of the blade to the first connection tube, a second connection tube and a second sensing port, the second sensing port fixedly attached to one of the suction-side skin and the pressure-side skin, and having a second through-hole connecting the exterior of the blade to the second connection tube, a pressure-sensing unit receiving the first connection tube at a first inlet port and receiving the second connection tube at a second inlet port, the pressure-sensing unit further having: a first resistive unit in fluid communication with the first inlet port, and a second resistive unit in fluid communication with the second inlet port, the first resistive unit and the second resistive unit also in fluid communication with ambient air at a preselected point so as to allow fluid passage of ambient air into the first and second connection tubes (161, 165), respectively, with a pre-determined amount of fluid resistance, and a differential pressure sensor producing a differential-pressure signal indicative of the pressure differential across the first inlet port and the second inlet port. a first resistive unit in fluid communication with the first inlet port, and a second resistive unit in fluid communication with the second inlet port, the first resistive unit and the second resistive unit also in fluid communication with ambient air at a preselected point so as to allow fluid passage of ambient air into the first and second connection tubes (161, 165), respectively, with a pre-determined amount of fluid resistance, and a differential pressure sensor producing a differential-pressure signal indicative of the pressure differential across the first inlet port and the second inlet port.