"James Sweet" wrote ...
"Doc" wrote...
Maybe, but a lot of people seem to swear by the Kill-A-Watt meter,
which can be had all day for around $25 online, eBay etc.

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.

Agree completely. They are great when used with the regular
sine-wave mains power grid. However note that many have
been fried beyond repair when used with any kind of square-
wave source: inverter, UPS, etc. even "stepped sine" waveforms.

The problem appears to be the capacitive voltage divider used
to power the Kill-A-Watt electronics. The high frequency harmonics
deliver way too much power to the shunt regulator through the
capacitor and something fries.