[Beowulf] Re: power usage, Intel 5160 vs. AMD 2216

[Lawrence Stewart]

On Jul 15, 2007, at 6:46 PM, David Mathog wrote:

> Greg Lindahl <lindahl at pbm.com> 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
> mathog at caltech.edu
> 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