Re: [opensuse] [OT] How much power does a PC really consume?

James Knott wrote:
Aaron Kulkis wrote:
James Knott wrote:
Doug McGarrett wrote:
On Friday 15 February 2008 08:15, Carlos E. R. wrote:
The Thursday 2008-02-14 at 12:06 -0500, Aaron Kulkis wrote:
I'm using one of these:


http://www.order.conrad.com/xl/1000_1999/1200/1250/1253/125319_AB_05_FB.

EPS.jpg
I would look for a device with a needle rather than
a digital readout.
I don't think you can measure true rms with a coil and needle. :-?

It was measured by thermal effects...

--
Cheers,
Carlos E. R.
There are electronic true-RMS voltmeters with analog readouts.
For example, the Balantine 323 has a nice big dial. You would have
to measure the voltage drop across a known value shunt resistor in
series with the load, and calculate the power from voltage and
current.

Ummm... He was talking about RMS, which implies voltage or current. There's no such thing as RMS power.

RMS is short for Root-mean-squared
i.e. _______
/ _ 2
V X

RMS can apply to any function vs. time (voltage, current,
power, etc.)


It's been a while since I've done it, but if you try calculating RMS power, you soon find your calculations are meaningless. The purpose of the RMS calculation is to determine the equivalent DC voltage or current that would produce the same amount of power. So, when you square a voltage or current sample you are in effect making an instantaneous power calculation P=E^2/R or P=I^2R, then taking the mean power value

And then taking the square root of the average of all of that.

over the cycle and then converting back to a voltage or current value.


RMS is just as statistical method, which is useful for making
sense of any time-variant function.

The square root of the square of power is just as much related
to power as the square root of the square of voltage is related
to voltage (NOT power).


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