[K12OSN] alternative power supply

Doug Simpson simpsond at leopards.k12.ar.us
Thu Dec 2 20:59:42 UTC 2004

And it is very easy at the breaker panel!

It is easy at the site, too.

Get one of those short grounded 3 wire extension cords that is *flat* 
where you can see all three wires with grooves between them.  Carefully 
split off one of the three wires and don't cut the insulation, just split 
it out there.  Then use a clamp-on ammeter to measure the current and do 
the math and it will tell you the watts.  This will work for *any* device 
you plug into that short cord.  Printers, monitors, computers, etc.

If you want to measure the current to a whole set, like CPU, Monitor and 
Printer, just plug them all into a strip and plug the strip into the short 
cord and measure away.

The math is:

Power 	Watts
over  	-------
	Volts X Amps

So if your measurement is 2A and the voltage is 120V, then the power 
(watts) is 240 (2A times 120V).

If you measure .5A then your watts is 60 (.5 times 120)

I measure things like this at home all the time.  You would be surprised 
just how many watts some things use!  And watts is what you pay for!

Doug Simpson
Technology Specialist
DeQueen Public Schools
DeQueen, AR 71832
simpsond at leopards.k12.ar.us
Tux for President!

On Thu, 2 Dec 2004, Angus Carr wrote:

> pnakashi at k12.hi.us wrote:
> >----- Original Message -----
> >From: Rob Owens <robowens at myway.com>
> >  
> >
> >>The best thing to do would be to actually measure the power 
> >>consumption.  You could do it on the input side and you wouldn't 
> >>have to open the case.
> >>    
> >>
> >
> >We have power issues in our school lab. I would really be interested in finding out how to do this. Anyone know?
> >--Peter
> >
> >_______________________________________________
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> >K12OSN at redhat.com
> >https://www.redhat.com/mailman/listinfo/k12osn
> >For more info see <http://www.k12os.org>
> >
> >  
> >
> Find an electrician with the right meter. You want them to measure AC 
> amps using an induction meter (I think). Given AC amps and nominal 
> voltage, they can tell you the wattage. They can also do it for whole 
> circuits at the breaker panel.
> Angus Carr.
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