Abstract: A method and an apparatus for measuring the wall thickness of a workpiece by ultra-sound is disclosed. For measuring the wall thickness, it is necessary to determine the time interval between a surface echo occurring during irradiation by ultra-sound and a rear wall echo. According to the present invention, a saw tooth generator generates a saw tooth signal including a sequence of saw teeth when the surface echo occurs. Each of the saw teeth causes a counting pulse to be generated. Upon occurrence of the rear wall echo, the instantaneous amplitude value of the saw tooth signal is measured and the number of counting pulses is recorded by a counter. Each counting pulse defines a constant unit of wall thickness. The amplitude value provides a fraction of such wall thickness unit.

Abstract: A continuously tunable function generator comprises a first function generator (10) with a triangle voltage generator including a comparator (24), which controls the commutation of a capacitor (14) from a charging phase to a discharging phase and vice versa in relation to an upper and lower preset amplitude value of the voltage at the capacitor (14). The triangle voltage (50) arising at the capacitor (14) is supplied to a second comparator (32) of another triangle voltage generator. The second comparator (32), commutates a second capacitor (38) of the same capacitance as the first capacitor from the charging phase to the discharging phase and vice versa. A reference voltage corresponding to the mean value of the upper and the lower amplitude value is applied to a second input of the second comparator. The charging currents and the discharging currents are identical, constant, and adjustable for changing the frequency of the triangle voltages.

Abstract: A transducer for launching ultrasonic test signals is stimulated by an electrical signal which is of trapezoidal contour. Particularly the trailing edge of the signal is to decline at a rate similar at least as to order of magnitude to the rise time, and occurring in synchronism with a natural zero crossing of the vibration of the transducer to fully develop at least one full ultrasonic oscillation.