Hi John:
> When conducting the voltage decay measurement, the measurement
> is either made with, or referred to, an instrument having an input
> impedance consisting of a resistance of 100 Mohms ± 5 Mohms
> in parallel
> with an input capacitance of 25 pF or less.
Agreed.
> So any 100: 1 probe can probably be used. I would expect the
> capacitance
> of a 100:1 probe to be much less than 15 pF, so just add extra shunt
> capacitance to taste.
Be aware that not all 100:1 probes have a 100 Mohm
input resistance. The 100 Mohm input resistance is
critical to the correct measurement.
The capacitance is of no consequence since the measurement
only applies if the capacitance is 0.1 uF or more. Probe
capacitances are in the range of 2 to 20 pF and are
negligible when in parallel with 0.1 uF. See my "Technically
Speaking" column in Volume 4, Number 4, December 2008,
issue of IEEE PSES "The Product Safety Engineering
Newsletter."
This is available to IEEE PSES members at:
http://ewh.ieee.org/soc/pses/society/08V4N4.pdf
Best regards,
Rich
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