Hi Frank:
> Interesting. During an audit of the facilities of a former employer, the
> auditor specifically requested that we didn't use the Simpson 228 for
> EN60950 because of the roll-off of the analog movement above 100Hz. The
> suggested fix was to build the network as described in the standard, with a
> high frequency true RMS digital meter.
Analog (D'Arsonval) meter movements are dc devices.
AC input is rectified and applied to the meter movement. Any
roll-off is a function of the frequency response of the rectifier
circuit, not the analog movement (since it only sees dc).
Furthermore, the network has a built-in roll-off such that very
little high frequency energy is actually applied to the measuring
device.
If your auditor had applied a constant voltage, variable frequency
ac source to the Simpson 228, he would indeed see a roll-off, the
one that is due to the frequency compensation network specified in
IEC 990. He would see exactly the same roll-off with the discrete
network and a wide-bandwidth true-RMS digital meter.
Best regards,
Rich
ps: I do not understand the source of leakage current that is
other than the mains frequency. In a switching-mode power
supply, virtually all of the high-frequency currents are
returned to the source via the EMC filter. Are there other
sources that are multiples (harmonics) of the mains frequency?
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