These came up for discussion over Xmas, and I had a look at prices,
It's interesting that quite a number come up for auction (ie not a
commercial seller) on Ebay - are they worth having, or are they just a
gizmo that are bought and then found to be just that.
The information these devices give need to be interpreted correctly with
an understanding of how they work.
Firstly they only measure current and I'm not sure how they cope with
non sinusiodal loads. There is no voltage or phase sensing.
1)So they will tend to over estimate power drawn by reactive loads. Such
as motors, fluorescent lighting etc
2)They wont take into account voltage variations or if you supply is
anything like mine, the severe 'flat topping' on the voltage waveform.
3)They may not measure correctly the power drawn by loads with switch
mode supplies eg most modern brown goods.
However, they will give indications when power is still being drawn when
you think most loads have been removed/reduced and so could well help
you track down possible power wasters.
Subtracting power readings when unplugging one particular device and
then expecting that difference to be the true power consumed by that
device needs care.
If you want to know haw much power is being taken by one device then the
plug in power meters are a better bet.
That's how I got mine, courtesy of a URL posted here by some kind soul
(IIRC when filling in the web form I had to use rather broad definitions
of being a British Gas customer and being an OAP...)
Seems to work in the sense that the readout goes through the roof when
someone puts the kettle on, but have no idea whether it's accurate.
(As I think I posted here before once, the device rather backfired when
it arrived, and the kids immediately started running round the house
switching everything ON in order to see how high a reading they could
On Wed, 30 Dec 2009 03:52:42 -0800 (PST), robgraham wrote:
Depends on how interested you are in your power consumption, how good
you are already at turning things off and if the thing can log data
and connect to a computer to produce graphs.
I have one and it's connected to the server that logs the data and
can produce a web page with a plot of a days consumption. It's
interesting in that the major pre cooking session for Christmas used
about 8 units of power over our normal use and the day itself 3 units
more than normal. The only thing that it has made any real change to
is tunring off the coffee machine after a hour or so instead of
leaving it on until the jug is empty and being better are knocking
off the 3kW kettle "keep warm" feature.
On Wed, 30 Dec 2009 13:51:30 +0000, BraileTrail wrote:
My server that I access over my LAN. It's not open the big nasty
CurrentCost CC128 Envi:
It logs and stores quite a history itself and squirts current data
out of its TTL level serial port every 6 seconds. TTL serial to USB
leads are available, though I made my own TTL to RS232 convertor. A
bit of Perl logs the 6 second data bursts and a bit of PHP produces
the webpage and plots via GnuPlot.
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