[conspire] check out AC power (Watt)meter (What's Your Watt?/...) from library

[Ross Bernheim]

One thing to remember about the Kill A Watt and similar consumer power/watt meters
is that they are meant for lights and appliances and while they will easily measure
a refrigerator or 100W light bulb, they are not accurate at low power levels.

The accuracy at low levels, typically below seven watts is not terribly useful. As
we move to LED light bulbs that only draw a few watts and very low power 
computers with solid state drives these meters may give inaccurate results.

One suggestion is to use a multi-outlet power strip and pair the device you want
to check with another device such as a light bulb that is a constant load above
ten watts so that you can accurately measure it then add the load you want to 
test and measure the increased load accurately.

All test equipment has limitations and you need to know what they are so 
you can assure the accuracy of your measurements.

Ross
 
 


> On Mar 18, 2015, at 3:44 AM, Nick Moffitt <nick at zork.net> wrote:
> 
> Michael Paoli:
>> One can check out AC power Wattmeter (What's Your Watt?) from
>> library.
> 
> These devices are really useful for installations where you have a lot
> of devices running.  You can accurately measure median loads, sample and
> get a rolling average, and take note of peak load (typically on startup
> for devices that have spinning rust).  
> 
> It's also amazing to look at two identical pieces of hardware and notice
> that they have dramatically different power loads. Often you can trace
> that to software load differences, and make adjustments as necessary.
> 
> But of course the best reason is for energy savings and capacity
> planning.  You can work out that your mains bus can handle N servers at
> normal load, and N/4 at peak load, or what have you.  Then you know to
> only start up a quarter of your systems at any one time, and stagger
> boots (or just increase capacity to cover full synchronised peak load).
> 
> _______________________________________________
> conspire mailing list
> conspire at linuxmafia.com
> http://linuxmafia.com/mailman/listinfo/conspire