Determining power draw on a system?

[Skyguy]

I see a bunch of reviews (mostly for graphics cards) that state the total system power draw.....to compare how power hungry a particular card or component is.

How is that total power draw determined? Is there some electronic measuring device (if so, where to get one)? Or is it done mathematically (which seems less accurate)?

I'm interested in trying to figure out the power draw on my various components and systems (ie--differences when I overclock more, and different graphics cards too) and would appreciate understanding how to do that.

Thanks!

[jonnyGURU]

To measure the AC power consumption of the whole PC, you would use a device like a Kill-A-Watt (http://www.thetwistergroup.com/store/customer/product.php?productid=P4400%20L02418&source=fr) between the PC and the wall.

To measure DC power consumption, you need a clamping ammeter that you can clamp around the DC wires feeding power to the particular device you want to know about.

For component level testing, you have to use a DMM that can measure amperage and know where on the motherboard the current flows through so you know where to apply the DMM's probes.

[Skyguy]

Thanks Jonny! I'll look more into those devices and see which would work best for what I need.

Much appreciated.

[clsA]

My APC UPS (XS 1000) tells me how much it is drawing from the wall
and i use a DMM for testing rails