Patent ID: 7640120

Claim:
A method for detecting an arc in a plasma process that is fed by an output signal of an AC generator, the method comprising: determining a first time at which an evaluation signal passes a first reference value in a first half-wave of the evaluation signal; determining a subsequent first time at which the evaluation signal passes a second reference value in the first half-wave of the evaluation signal, the first time and subsequent first time defining a first time interval; determining a second time at which the evaluation signal passes the first reference value in a second half-wave of the evaluation signal; determining a subsequent second time at which the evaluation signal passes the second reference value in the second half-wave of the evaluation signal, the second time and the subsequent second time defining a second time interval; comparing the first and second time intervals; and generating an arc detection signal if the first and second time intervals differ from each other by more than a predeterminable tolerance.