Abstract: By the fastening device, two electric transmitters are to be arranged on a supporting structural part from which two extensions (11) protrude spaced from each other. For this purpose, one bored attachment end (15, 16) each of the two transmitters are arranged each on one side (13, 14) of one of the two extensions (11) on a threaded bolt (1, 2). The threaded bolt is screwed, with one collar (5, 6) each lying on both sides against the extension (11), directly to the latter. The attachment ends each have such a large recess (20 22) that they rest only on the extension without resting on the collars (5, 6). The threaded bolt (1, 2) is provided on the outside on both ends with a threaded section (9, 10). Nuts (25, 26) which are screwed on the respective threaded sections press in each case one of the two attachment ends (15, 16) against the extension (11).

Abstract: One or more dimensions of a workpiece, such as sheet material, are determined by passing the material between opposing linear arrays of ultrasonic transmitting and receiving transducers. The dimension of the sheet material is a function of the number of receiving transducers which receive a transmitted signal as compared to the number of receiving transducers which no longer receive a transmitted signal due to blockage of the signal by the sheet material. The strength of the signal is a function of the amount the receiving transducer is blocked by the workpiece, which in turn is a function of the position of an edge of the workpiece relative to the receiving transducer. A more accurate determination of the workpiece dimensions is obtained by establishing various threshold levels of signal strength and by comparing the receiver signal to these threshold levels.