Charlie wrote:
"Michael J. Mahon" <mjmahon@aol.com> wrote in message
EO2dnbf-V-o4B8rbnZ2dnUVZ_h2pnZ2d@comcast.com">news:EO2dnbf-V-o4B8rbnZ2dnUVZ_h2pnZ2d@comcast.com...
mspangler wrote:
To figure out how long my data collection Apple II would run on its
UPS, I put a Kill-a-watt meter on it. It pulls 24 VA (not counting the
monitor). My Mac mini (dual core 1.66 GHz) pulls 28 VA if the optical
drive is not running. So you're not necessarily as much greener as you
may think.
I just got one of those yesterday!
Did you look at the power consumption (not allowing for power factor)?
(After all, the Apple II power supply was *way* before power factor
correction. ;-)
Do any computer power supplies sold in the United States have power
factor correction? I believe they are standard in Europe but I'm not
sure about the US.
Europe was quicker to lower the power levels requiring PFC than the US,
but progress up the learning curve for PFC supplies, higher integration
levels, and the economies of making "global" power supplies are pushing
PFC into more power supplies every day.
Higher powered supplies will be the first to go to PFC, of course.
Also, in another newsgroup a poster argued that the Kill-a-watt meter
isn't accurate when used with a computer due to the switching power
supply. He claimed that the Kill-a-watt meter needed a true sine wave
for accuracy and that the switching power supply warped the normal AC
sine wave. I have no idea as to the validity of that argument but
figured you would be the guy to ask.
I don't know the circuit of the Kill-a-Watt, but, since it makes a
distinction between watts and VA, and clearly is controlled by a
microprocessor, it is not unreasonable that it computes using the
actual sampled waveforms for current (if not voltage, which is almost
always sinusoidal unless it's locally produced by an inverter).
It would be possible to so some experiments to find out, but probably
easier to try to find documentation on the design.