Grinder wrote:
On 2/12/2011 2:42 PM, Just Wondering wrote:
Are there any Powersupply unit monitoring applications or utilities
that can tell me how many watts of power I am using at a givent time?

I don't know of any software, and I have my doubts software could even
do that, but you can buy a relatively inexpensive device called a
killawatt:

http://www.amazon.com/s?ie=UTF8&inde...ords=killawatt

The Killawatt device is the right answer, because it shows the
power that is coming from the wall, taking ATX power supply
inefficiency into account.

A clamp-on DC ammeter can be used to make contact-less current
measurements, using the power cables on the power supply. I make
power measurements on systems here, using such a device. For
example, if I clamp my meter around the two yellow wires
feeding the CPU Vcore circuit, right now it would read 1.1 amps DC.
Time 12V gives 13.2W while the computer is idle. (That is my wasted
CPU power.) You have to measure all the rails, one at a time, with
the clamp-on meter, do your times and sums, and get a total power
that way. That gives power *inside* the computer, and doesn't take
into account the fact that the power supply is 68 to 87% efficient.

(Example of a clamp-on ammeter, which senses the magnetic field around
a set of wires, and measures the current that way. These come in AC only and
AC/DC models, and you need DC capability to measure inside the computer.
Mine is nicer looking that a lot of these.)

http://www.gd-wholesale.com/userimg/...imeter-480.jpg

The motherboard has *no* ability to measure power consumption.
They don't put current shunts into any of the rails, to make
such a measurement. The Xbitlabs people, specially modify their
motherboards with added current shunts, in order to do power
measurements for their web articles.

There have been special power supplies, with measurement capabilities
built in. But I wouldn't trust such designs, further than I can throw
them.

Using the Killawatt, avoids all that detail, and just gives you a
final number for the computer enclosure. No wasted time, no
monkeying about.

One nice feature, is the Kill-A-Watt features a KWH measurement.
Say your mom insisted you pay her, for all the power your computer
was using. You could turn on the P4400, and it keeps track of the
total power used in real time (Kilowatt-hours). Say in a month,
you used 100 KWH and the utility charges $0.07 per KWH. You could
give your mom $7.00 for the month, then reset the P4400 and meter
for the next month.

http://www.p3international.com/manuals/p4400_manual.pdf

Paul