Re: Green Apple Small Carbon

["Charlie" <charlieDOTd@verEYEzon.net>]

"Michael J. Mahon" <mjmahon@aol.com> wrote in message 
8Z-dnRDgC87_C8XbnZ2dnUVZ_judnZ2d@comcast.com">news:8Z-dnRDgC87_C8XbnZ2dnUVZ_judnZ2d@comcast.com...
> Michael J. Mahon wrote:
>> 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.
>
> After reading around a bit, I was unable to find anything definitive on
> the design of the KAW, but I did find a reference to it using a custom
> DSP and 12-bit ADCs, so if we knew the sampling frequency, we'd know
> how accurate it can be with waveforms with high harmonic content.

Here's a site with pictures of the circuit boards:

http://cafeelectric.com/killawatt/

> Many users seem to be using it to size inverter supplies, so that would
> indicate that it is reasonably accurate for non-sinusoidal current and
> voltage waveforms.  Not bad for such an inexpensive device.

I Agree.

Charlie