22 Dec
2011
22 Dec
'11
9:57 p.m.
I doubt tony
needs to be told this, for two different reasons, [...]
THe 2 reasons being (a) I
haev a 'scope and (b) I know the trick anyway? [...] an AC
voltmeter in series with a moderately large capaci-- um,
condenser, for DC isolation. [...]
What you need is that the impedance of the
capacitor at the mains
frequency is small compared ot the input resistnace of the meter. A 1uF capacitor should be fine for most cases. [...]
One advantage
the 'scope has though, is that it lets yo see the ripple frequency.
Actually, if you don't have a 'scope, you can get _some_ idea of the
ripple spectrum by trying multiple different cap values, with known
resistors in parallel across your meter if it's particularly high
impedance (like the >10M tony mentioned). You likely will have to do
some arithmetic, though.
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