Patent US 5,221,825

A method of sensing and controlling a gas metal arc welding process employs high frequency sampling of electrical signals from the welding circuit. The sampled signals are operated upon by predetermined processes to determine characteristics indicative of on-going weld quality and the future weld quality. The processes which operate upon sampled electrical signals determine shielding gas quality, the occurrence of short circuits and frequency thereof; pulse frequency and standard deviation thereof, contact tube wear and trends in the sampled electrical signals.