On Jul 15, 2007, at 6:46 PM, David Mathog wrote:
Greg Lindahl <[EMAIL PROTECTED]> wrote
So, the thing that logs power usage over time seems to be the "Watts
Up Pro", which says that it plugs into USB and has a Windoze
program that
graphs power usage. Does anyone have one, and can you access the data
sans Windoze program? Are there any other cheap logging power meters?
The Watts Up Pro is only $130 at Amazon right now - if your
time is worth anything just buy one.
If this is a one time deal and you have a USB Camera you
set it to snap pictures of the display at fixed intervals, and
then scan through those later.
Or, if you already own a USB data logger and a Kill-a-watt, try
this at your own risk. Most likely you'll end up filing the effort
under "I wish I'd just spent the money on the data logging version"!
On opening up a Kill-a-watt you'll find that one side has all the
power
goodies and a tiny amount of logic, and the other side contains the
display, the buttons, and what looks like the logic to control the
display. The two sides are connected by a 6 wire cable, where
all of the wires are the same diameter, with no shielding and no
twisted pairs. It seems likely that if one attached a voltmeter
to those 6 wires one would find a ground, 5V (or 12V) dc, and
4 measurement lines, probably representing Line Voltage, Current, Line
Frequency, and Power. If you're lucky the measurement values are
encoded as a DC voltage. That would be easy to test, and if true,
you could solder leads onto those 6 lines and bring them outside
the case to attach to the input leads of your existing USB data
logging device.
Regards,
David Mathog
[EMAIL PROTECTED]
Manager, Sequence Analysis Facility, Biology Division, Caltech
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If memory serves, the Kill-A-Watt has no internal grounding and no
protection. Unless you put an isolation transformer in front of it
and ground what you think is the ground side of the "logic", any wire
inside you tap into is likely to be "hot".
This thing costs only $30. It's not really intended for extensibility!
-L
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