Patent ID: 7036376

Claim:
A welding system, comprising: a device for evaluating an ultrasonic signal during a welding process, having a measured value evaluation unit ( 43 ) that, in normal operation, evaluates at least one measurement signal (Ue) that is derived from an ultrasonic signal and is located inside a measurement window (t m1 , t m2 , t S1 , t S2 ), wherein at least one measurement signal (Ue) determination means ( 35 , 37 , 39 ) for establishing the measurement window (t m1 , t m2 , t S1 , t S2 ) is provided that establish the measurement window (t m1 , t m2 , t S1 , t S2 ) according to a measurement signal (Ue) that is received in a calibration operation, further comprising a first electrode and a second electrode, wherein material to be jointed is situated between the first electrode and second electrode, such that the material is accessible from two sides, wherein a zero transition point determination unit ( 37 ) is provided that determines the zero transition point of the amplitude of the measurement signal (Ue), whereby the measurement window (t m1 , t m2 , t S1 , t S2 ) is established according to an output signal from the zero transition point determination unit ( 37 ).