What is the unit of power level in the Dragon Ball series and how is it measured? Throughout almost the entire series, all characters in the Dragon Ball series keep on talking about sensing each other's powers from great distances and all. They even compare each other's power levels just by observing each other.

So my questions are:


What is the unit of power level? For example, weight is measured in the unit kilogram.
How is each unit of such a power measured?
Since the story revolves around Earthlings, is it possible (in the wildest of dreams) for humans to devise a way to measure power levels?
I think the unit of the Power Level is Ki. I would like to give you the link to the wiki:


  The Power Level (戦闘力, Sentō Ryoku; literally "combat power" or "fighting strength"), 
  referred to as Battle Point/Battle Power (BP) in video games, is a
  concept found in the Dragon Ball franchise created by Akira Toriyama.
  It is first introduced in Dragon Ball, where Goku as a kid learns to
  sense ki after drinking the Ultra Divine Water, although the Z
  Fighters are able to detect power levels via the ki sensing ability
  eventually.

It's not clear how they measure the power, or at least I couldn't find something...
That's right, Bulma got one of the scouters, so I think it shouldn't be a problem for her to copy it.


And if you want to know which character has which Power Level, see this list of Power Levels.