The invention relates to an ultrasonic sensor system, especially for
controlling a resistance welding process. Said system comprises at least
one receiver which is used to detect the ultrasonic signals from the area
to be examined. At least two piezoelectric sensors (31, 32) are used as a
receiver and are arranged in such a way that their polarization direction
vectors indicate various directions, said vectors being projected in a
plane perpendicular in relation to the propagation direction of an
ultrasonic wave to be detected.