What does your touch current look like? Making proper touch current measurements

This paper responds to continued questions regarding the measurement of non-sinusoidal touch current with `spikes' as introduced by Switched Mode Power Supplies and their performance modifiers - PFC correction circuits and Energy Efficiency control circuits. The history is given to provide the proper background, The IEC electric shock level requirements are reviewed especially pointing out the factor of safety designed into these requirements. The allowance for high-frequency components is discussed as included in the IEC 60990 touch current measurement circuits. Examples are shown for AC, DC and mixed AC/DC waveforms with emphasis on the peak values and their proper measurement.