[PLUG] Kill-a-Watt (was LCD thingies)

Keith Lofstrom keithl at kl-ic.com
Sat Dec 2 06:41:40 UTC 2006


Keith Lofstrom wrote:
>(this is measured with my Kill-A-Watt power meter,
>available from GoLinuxShop for $18.13, see http://snurl.com/13uq0 ).

Denis Heidtmann wrote:
> What is the maximum current that meter will handle?

Maximum is 15A, 125V.  It only measures down to 0.01 Amps, so low
power devices like wall warts don't register accurately, but it
seems to be accurate within a watt or so.  It can measure VA 
(including reactive currents), and measure accumulated kilowatt
hours as well.  I was surprised to find that our refrigerator 
averages only 47 watts over the course of a day, and that the 
Thinkpad AC adapters I leave scattered all over do not register
even 1 watt when not driving a laptop.

BTW, I use an instrument called a "curve tracer" to look at
the AC adapters in more detail - they consume 5mA of "reactive
current", and no measurable "resistive current" when running
unloaded, which means that they only cause a milliwatt or two
of extra generator load to the power company - power line heating
losses out to the substation where the phase correctors are - but
nothing like the 1 or 2 watts that an unloaded wall wart consumes.  

It is educational to measure the power consumption of devices
in the office and the house.  The biggest current draw in my
computer lab is the Tektronix Phaser 350 color "crayon" printer.
Our largest "electrical sin" for our house is our water heater,
due to my daily hot soaky baths in the evening.  I will have to
work on that ...  but not now, it is time for my bath :-)

So buy some power meters, and give them as Christmas gifts.  Your
soon-to-be-ex friends who should use less electricity will be
reminded of your strident hectoring even when you are not there!

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs



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