> A meter for IEC 60950 may not be adequate for IEC 61010,
> especially if the unit under test has a reasonably high
> frequency switch mode power supply.
The high frequencies generated in a switching mode power supply
are negligible in the presence of the mains-frequency leakage
current (presuming that the SMPS as even a mediocre EMC filter).
Even if high frequencies are present in the leakage current, the
various leakage current measurement schemes use a capacitor to
shunt the high frequencies around the metering circuit.
The body response to electric energy falls off rapidly for
frequencies above 1 kHz. At 100 kHz and above, the injury
changes from shock to burn, and the limit is 70 mA peak (50
ma rms!). Consequently, the leakage current meters include
frequency compensation to account for the body response.
Around the turn of the century, D'Arsonval performed an
experiment where he lit a 100-watt bulb at a frequency between
10 and 100 kHz with ALL of the current passing through the
human body! No injury!
Richard Nute
San Diego
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