Instruments for studying the welding arc

FOR THE purposes of this investigation, the number and duration of the short circuits in the arc and the degree of voltage and current fluctuation have been taken as an initial basis or criterion for stability measurements. Electronic circuits have been developed to detect and count all short circuits whose durations exceed a given specified time, such as a millisecond, and record the count on an electromechanical counter. The proportion of the total time that the arc is short-circuited is measured by a simple vacuum-tube circuit known as the short-circuit-duration indicator, and indicated on a suitably calibrated milli-ammeter. The average duration of the short circuits can be computed from the readings of these two instruments.