Subject:
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RE: Monitoring household power consumption
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Wed, 11 Nov 1998 19:00:53 GMT
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Original-From:
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brett anthony <anthonyb@ecs.csus+nomorespam+.edu>
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Viewed:
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2429 times
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Actually, that little black band is a relic of earlier days when people
(like myself) had jobs that occasionally required them to sit with a
stopwatch and count turns. A slide rule was then used to calculate power
consumption. Each meter had a unique "meter factor" which entered into the
equation. You actually might not have such difficulty using an LED
emitter/detector pair to count turns if you shield the meter from ambient
light. Of course, if you remove the glass dome to get closer to the disk
the power company will send the sheriff...
The problem with the meter disk is it only spins fast if you are using a lot
of power, so if you want to track individual small appliances you would have
to run them a really long time with everything else unplugged. Remember,
many devices like TV's , radios, doorbells, stoves, ovens, HVAC, and
telephones, or anything with a built-in battery charger or clock, or
anything that runs from a "wall wart" (AC adapter), or anything that uses
refrigeration, or has a built-in microprocessor; will use power even when
shut off. Just for the hell of it, turn off everything you can think of,
then take a flashlight and go watch that disk...
All of which is to say that finding the Circuit Cellar article referred to
by Tom Brusehaver is a good idea. Presumably the article provides some way
to convert the coil output to DC. You could also buy/borrow/rent a current
meter or current probe for your multimeter if you own one. These use the
same principle, except the toriod is hinged so you can snap it over the hot
wire without having to disconnect anything. You can then make a power
survey for each circuit in your house by snapping the meter over the
relevant wires in your breaker panel. To run a long term survey for the
whole house you need to make and calibrate your own coils. Note that if
your house is wired in the normal way you need two.
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