Method and apparatus for monitoring short circuits in electric arc welding

Claim 1

A METHOD FOR DERIVING A SIGNAL FROM A SHORT CIRCUITING CONSUMABLE ELECTRODE ARC WELDING CYCLE WHICH COMPRISES PERMITTING CURRENT TO FLOW IN A MONITORING CIRCUIT WHEN THERE IS ANY ARC VOLTAGE WHILE PREVENTING CURRENT FROM FLOWING IN SAID MONITORING CIRCUIT WHEN THERE IS A SHORT CIRCUIT CREATED BY THE PHYSICAL CONTACT OF THE CONSUMABLE ELECTRODE WITH THE WORK, THEREBY MONITORING THE SHORT CIRCUIT CYCLE, DERIVING A SIGNAL FROM SAID MONITORED SHORT CIRCUIT CYCLE, THE MAGNITUDE OF WHICH VARIES AS A FUNCTION OF THE SHORT CIRCUIT DURATION, PROVIDING A TIME BASED REFERENCE THE MAGNITUDE OF SUCH REFERENCE BEING NO GREATER THAN ABOUT THE DURATION OF SAID SHORT-CIRCUITING CYCLE, AND COMPARING SAID DERIVED SIGNAL WITH SAID REFERENCE TO PRODUCE AN OUTPUT SIGNAL.