"James Sweet" wrote ...
"Richard Crowley" wrote ...
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.


Interesting, well mine is the 240V UK version which I got back before I
found them offered here but from looking at the buttons and display it's
obviously the same unit as the Kill A Watt. At any rate I've tested it and
it works well all the way down to 60VAC, and frequencies from 30 Hz all
the way up to nearly 400Hz where the readings start to get screwy. I've
run it off inverters, used an adapter to hook it up to my 240V central
heat pump to measure that, it's taken everything I've tossed at it and so
far keeps working.

There are rumors that the manufacturer re-designed the
circuit to eliminate this flaw. It may not be a problem with
newer models(?)

The original problem was featured in a 2-page article in the
ham-radio magazine "QST".