Abstract: In an electrical spot welding machine having sensor leads for monitoring weld nugget resistance connected to the electrodes or to the welding current conductors, the voltage component induced in the sensor leads due to inductive coupling is cancelled out by inducing a substantially equal and opposite compensating voltage in the sensor leads. For this purpose an inductance coil may be connected into one of the sensor leads and appropriately positioned on one of the welding current conductors. A core-less coil can be employed, and correct adjustment of the compensating voltage can be achieved by adjusting the coil angularly with respect to the axis of the welding current conductor.