Abstract: A method and an apparatus for transmitting and receiving electromagnetic ultra-sound, especially in non-destructive testing of electrically conductive material, comprising the steps of generating one or more magnetic fields by means of one or more electromagnets (1,2,3,4) and supplying a transmitter coil (8) in said magnetic field with a supersonic frequency, and scanning a receiver coil (56) in said magnetic field. In known apparatuses, especially in the testing of non-magnetic material, the signal/noise ratio of a received signal is unfavorable.According to the present invention said ratio is improved in that said magnetic field is generated during a short time compared with the time between two successively occurring magnetic fields, and that a number of pulses of well-defined length of supersonic frequency are supplied to the transmitter coil (8) when the magnetic field or fields have a sufficient strength.

Abstract: A method of, and apparatus for, regulating the bath level of a continuous casting mold by means of electromagnetic alternating fields which contemplates measuring changes in the inductance as a function of the bath level and employing such measured changes as an input signal for bath level regulation. According to specific aspects of the invention an electromagnetic primary alternating field is directed at one mold wall from the side of the continuous casting mold where the molten metal is poured-in. This alternating field induces a current in the mold wall and a secondary electromagnetic alternating field produced by such current is measured and employed as an input signal for regulation of the bath level in the continuous casting mold.