Voltage-current sensing system for welders and the like

Claim 1

In combination with an arc welder having a power source and a cable that conducts welding current, a core of magnetic material magnetically coupled to said cable, a switch immediately adjacent said core and which closes in response to a predetermined value of magnetic flux induced in said core by said cable in response to welding current flow through said cable, an AC source of power, a recorder, first and second full wave rectifying bridge circuits connected in series between said AC source of power and said recorder, each rectifying bridge including four diodes in the respective four legs of the bridge circuit and a silicon controlled rectifier connected in the direct current to conduct current in the output leg upon actuation of the gate of the silicon controlled rectifier, output leg of each bridge circuit means responsive to the closing of said switch for actuating the gate of the silicon controlled rectifier of the first bridge circuit, a third diode full wave rectifier having input terminals connected to sense the voltage output of the welding power source and input terminals output, and means responsive to a predetermined voltage at said output terminals for actuating the gate of the silicon controlled rectifier of the second bridge circuit, whereby a circuit to said recorder will be completed only upon simultaneous occurrence of predetermined values of welding current and voltage.