Re: [TCLUG:22753] Measuring power consumption (was MP3 player)

[Adam Maloney <adamm@sihope.com>]

Oh yeah, I've got one right here...

Incidentally, Radio Shack has a nice little pocket meter that runs about
$20.  From memory it does AC/DC voltage, impedance, and continuity.  It's
pocket-sized, very good stocking stuffer.  As I remember they go on sale
every year just before christmas.  I carry it around in my backpack (along
with my Slackware install disks and CD) for those emergency situations
where lives depend on having a multi-meter close by.

Adam Maloney
Systems Administrator
Sihope Communications

On Tue, 17 Oct 2000, Ben Kochie wrote:

> why not just use an inductive curent meter?
> 
> Thank You,
>         Ben Kochie (ben@nerp.net)
> 
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> 
> On Tue, 17 Oct 2000, Bill Layer wrote:
> 
> > The multimeter will do just fine but you will have to play one trick or 
> > another to make the necessary series connection with the power cord to 
> > measure current draw.. I have a special, short extension cord that has one 
> > conductor broken so that the meter may be inserted in series with the loop.
> > 
> > Set the meter for the current scale and measure the current draw with the 
> > device powered on. Then, keeping the device powered on, set the meter for 
> > an AC RMS voltage scale and measure the supply voltage at the wall - it's 
> > not wise to estimate, as AC mains voltages can be anywhere between 109 and 
> > 126VAC - with 117 being nominal. Once you know current and RMS supply 
> > voltage, power (wattage) calculation is this easy:
> > 
> > P = E * I (Where P is power (in watts), E is energy (in volts) and I is 
> > current (in amperes))
> > 
> > I should mention that most all (even inexpensive) meters automatically give 
> > AC voltage readings in RMS - so don't get too concerned about this issue. 
> > If the meter doesn't say otherwise, it's giving the reading in RMS.
> > 
> > 
> > 
> > 
> > 
> > 
> > 
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