In comp.sys.ibm.pc.hardware.misc James Sweet wrote:


EE friend of mine compared one to a $2500 power analyzer at work, found
that
the Kill A Watt performance is pretty much inline with the specs printed
for
it. It's not as good as the professional equipment, but it's really very
impressive for what it is and certainly adequate for consumer use. The
wonders of modern microelectronics, it's amazing what they can do with
one
inexpensive chip and a handfull of passive components. I still remember
when
a pocket calculator was $300, then a few years later $50 would buy one
just
as effective, and not long after that they were under $20 and those are
all
more capable than large machines costing many thousands just a few
decades
earlier.

Hmm. Interesting. I trust he did this right and tested non-ohmic
loads such as a PC PSU as well?



Yes, of course, pure resistive loads can be measured just fine with a
multimeter. We were interested primarily in using it to measure discharge
lamp systems in which the power factor and current waveforms can be all over
the place and vary greatly with the state and condition of the lamp. If the
meter wasn't able to handle odd waveforms, the power factor measurement
function would be useless, but it works pretty well, accuracy is within
about 2% on the sample tested.



Good to know, so it _can_ be done relatively cheaply today.

Arno