Abstract: An arrangement for automatically tracking systems to the center of weld gaps, weld joints or weld reinforcements, in which one or more electrically scanning probes receive signals reflected by a workpiece surface as long as this surface is substantially parallel to the acting surface of the probe. The signals breakdown spontaneously when the surface clearly deviates from the parallel as in the case with the flanks of gaps, joints or reinforcements. The breakdown of the signal is applied for storing an electrical value corresponding to the instantaneous probe position, the probe position for the left flank when traveling from left to right and for the right flank when traveling from right to left. The center of the gap, of the joint or of the reinforcement is computed from the stored electronic position values in a series-connected electronic device, by means of a computer circuit.