Willems, H.H.WillemsBarbian, O.A.O.A.BarbianHuebschen, G.G.Huebschen2022-03-082022-03-082004https://publica.fraunhofer.de/handle/publica/306520The tester incorporates two stray flux magnetisation units (3,4) in the form of U-shaped permanent magnets with axially aligned pole pieces (5,5',6,6') joined by a yoke (7,8). One unit (3) has an electromagnetic ultrasonic transducer (9) radiating at right angles to the static magnetic field. Another transducer (11) radiates parallel to the static field from a position between the neighbouring opposite poles of the two units. The function of these is solely to premagnetise the material under investigation and to measure the stray flux. USE - In pipelines (2) or similar structures. Sufficient signal/noise ratio is achieved by suppression of Barkhausen noise when transducers are moved.de608620658670patent1995-19543481