RESISTANCE WELDING MONITOR

A resistance welding monitor comprises a half-wave amplifier for half-wave amplifying the voltage across the electrodes of a resistance welder at the time of welding, a memory circuit for storing the maximum value of the output waveform from the half-wave amplifier, and an operating circuit for calculating the output from the memory circuit on the basis of a predetermined constant in order to decide whether the welding operation is satisfactory or not. A comparator-detector circuit compares the output of the operating circuit with that of the half-wave amplifier to detect only a positive wave, and a delay circuit is provided for smoothing and delaying the output from the comparator-detector circuit. The output from the detector circuit is applied to a decision circuit which in turn develops an alarm pulse through a reference pulse generator circuit on receipt of the output from the half-wave amplifier, and the alarm pulse is passed on to actuate an alarm circuit only when the output from the delay circuit is applied to the operating circuit, thereby detecting an unsuccessful welding result, simplifying the welding operation under various welding conditions.