A device and method for inspecting and measuring weld defects in a cylindrical wall of a cylindrical conduit. The device can include an inspection head forming a probe having a proximal end and a distal end along its longitudinal axis, and of which a first side called “inner side” is provided with at least one ultrasound wave transducer. The inspection head can include a second side, called “outer side” opposite the first side that has a curved surface in the form of a cylinder fraction, and wherein the curved surface of the second side has outward facing convexity. The wave transducer can be formed of a series of juxtaposed elements, each element being both a transmitter and receiver, wherein a surface of the series is curved and in the form of a cylinder fraction, and wherein the surface of the series has outward facing concavity.