Tom said:
>By the way, a typical o-scope is one of the least reliable
common ways to read power. First, scopes have passband
ripple. They are designed of good response to a stepped
waveform, frequency response flatness (or lack of ripple) is
secondary. Second, they are susceptible to common mode on
probe leads. Third, they don't store the absolute peaks
unless you have a storage scope and are lucky enough to
catch the peak. Fourth, any error they do have is compounded
by the fact power is a square of the measured voltage, so
the error is squared. Fifth, they are load resistance
critical.<
Sixth: most scopes are only good to about 5% measurement uncertainty anyway, so
from Tom's point 4, that error gets squared. And if there's a probe used, that
adds to the uncertainty, too. OK for a rough reading...
73
Peter G3RZP
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