Abstract: In crack-sensing equipment for hot steel strands, a movable transducer is linked to its sensing electronic circuit via an inductive transmission link to obviate the use of flexible conductors and/or slip couplings.

Abstract: A device for simulating a moving test object sensing transducer uses a plurality of individual transducers which are stationary relative to each other (for example eddy-current based surface transducers), and a selector unit. The individual transducers are, for example, mounted in a plane parallel to the surface of the test object to be sensed and scan the test object with respect to a characteristic, for example a crack. The resultant simulated transducer signal is signal processed by means of, for example, automatic compensation and vector transformation techniques.

Abstract: An eddy current testing device for inspecting test objects, for example billets, with respect to surface defects, for example surface cracks, comprises at least one transducer/sensor, for example a surface transducer or surface transducer arrangement, which is made to scan the surface of the test object. The device is characterized in that the effect of harmless surface blemishes on the testing device is suppressed, at least partially, by compensating for the sensitivity characteristic, in the scan direction of the transducer/sensor, with respect to the surface defect.

Abstract: A defect-sensing device for a test object, e.g. for detecting cracks in metal bodies with the aid of the eddy-current technique, has improved phase-selective properties by adding at least one product and/or quotient former to the signal processing equipment. The output signal from an ordinary phase-controlled rectifier can be substantially described via sin .alpha. and/or cos.alpha. functions in which indicates the phase position of the control signal in relation to the input signal. By multiplying sin.alpha. by cos .alpha. sin 2.alpha. cos 2.alpha. functions are obtained which in turn can be multiplied to obtain the function sin 4.alpha. corresponding to narrow sensitivity lobes in the transducer's impedance plane, thus permitting effective separation of the various types of vector signal resulting from detectable defects.

Abstract: An electrical defect testing device for a non-magnetic test object, for example crack detection on hot continuously cast billets, is provided with means for detecting and suppressing the influence of disturbing magnetic regions of the object (e.g. regions of cold oxide scale). The device comprises at least one sensing transducer for harmful faults which is adapted to move relative to the test object. At least one detector is associated with the transducer for identifying the presence of magnetic material, and a blocking circuit is provided which, directly or indirectly, is controlled by the magnetic detector and is used for suppressing signals originating from a fault vector, for example a signal indicating a harmful fault. The presence of magnetic material can be detected using an eddy current technique.

Abstract: An eddy current testing device for inspecting test objects, for example billets, with respect to surface defects, for example surface cracks, comprises at least one transducer/sensor, for example a surface transducer or surface transducer arrangement, which is made to scan the surface of the test object. The device is characterized in that the effect of harmless surface blemishes on the testing device is suppressed, at least partially, by compensating for the sensitivity characteristic, in the scan direction of the transducer/sensor, with respect to the surface defect.

Abstract: Defect detecting equipment includes a device which detects the presence of, for example, disturbing magnetic material such as cold oxide scales in a test object, in order thus to control, for example, that disturbances of a magnetic origin are not confused with surface cracks without being discovered. By utilizing eddy current techniques, phenomena which are harmless to the process can be separated from dangerous surface cracks, thus avoiding the scrapping of crack-free test objects. The invention is based on signal-processing at least two signals, for example H1 and L1, originating from a test object sensing tansducer, by means of a vector transformation method, and distinguished between harmful and harmless phenomena (e.g. cracks and oxide scales) as a function of a comparison of signals, S1 and S2l , from at least two transformation blocks.

Abstract: A testing device for storing and/or processing of fault signals obtained from at least one transducer with associated electronic equipment, which fault signals are at least partially derived from one or more features, for example a defect on a test object, such as a steel blank. The fault signals are supplied to at least one discriminating circuit to distinguish between relevant and trivial fault signals. The relevant signals are then supplied to a plurality of different signal processing circuits which, for example, operate in parallel but independently.

Abstract: A device for quality testing hot test objects, comprises at least one coolant-cooled rotatable body, and at least one transducer (for example a surface transducer coil) eccentrically mounted in or on the body to move along an endless path in close proximity to a surface of the test object. The transducer is conncted directly or indirectly to an associated sensing circuit. A device according to the invention is characterized in that the flow of coolant is adapted to take place via an inlet channel and an outlet channel, both of which are disposed close to the axis of rotation of the body, and at least one further channel extending between the inlet and outlet channel to convey coolant at least close to the transducer(s).

Abstract: A device for measuring or testing of an object, for example rolled wire, a tube, or a billet, to detect surface discontinuities employs a sensing transducer which is oscillated backwards and forwards over the surface of the test object by means of a motor, the oscillations taking place in the form of a curved path extending transversely of the longitudinal extent of the object.

Abstract: A device for transmission of signals between two units which are movable relative to each other without having to use rotating slip rings or the like. The signal transmitting conductors are disposed close to a point on the center axis of a rotating holder for the signal source. This results in minimum fatigue of the conductors, which in turn permits a long life of the conductors. The signal source is journalled in the holder and can be prevented from rotating around its center axis. The device can also be used to transmit a medium such as a coolant between two units.

Abstract: A method for testing an electrically conductive test object with regard to an imperfection therein uses a transducer supplied with drive signals of two different frequencies so that via inductive coupling between the transducer and the test object, signal information is received from the transducer which can be processed to indicate the presence of an imperfection. The invention is characterized in that the transducer is designed and supplied with drive signals in such wise that the effect of the different depth penetration of currents induced in the test object at the two frequencies can be compensated for.

Abstract: In the testing of electrically conductive test objects for the presence of flaws and the like using a transducer to generate electrical currents in the test object and to inductively sense such currents, drive signals of at least two different frequencies are use for the transducer and the different frequency component induced signals picked up by the transducer are processed in such ways that a testing process is obtained that has low LO (lift-off) dependence. The characterizing feature of the invention is that the signal processing is undertaken as a function of at least one variable which may be the lift-off distance.

Abstract: During so-called eddy current testing by way of several frequencies, it is often difficult efficiently to separate and detect superficially located defects from the disturbances caused by a varying distance from the transducer to the object under test. This is due to the fact that the fault direction and the lift-off direction normally differ from each other to too small an extent and the fact that the signal processing, which is necessary for the suppression of the lift-off dependence, also suppresses the fault signal. This problem can be eliminated completely or partially by means of the present invention, which comprises selecting the used frequencies in such a way that, in relation to the depths of cracks occurring, they fulfill certain conditions, one of which being that at least one frequency is relatively insensitive to the defect in question. This effect is achieved by selecting such a high frequency that its depth of current penetration is limited seen in relation to the depth of the defect.

Abstract: A method and device for nondestructive testing of articles using the eddy principle current and multifrequency technique. The characteristic feature is that the measurement is generally independent of the position of the article to be tested in relation to the pickup probe. In comparison with known devices the present device is easy to handle.