[rescue] Onyx question

[Jochen Kunz]

On 2002.08.01 23:46 Joshua D Boyd wrote:

> So, anyone have a handy method for converting a steady pull of
> 7A to kilowatt/hours per day, since someone so kindly pointed out
> recently that in AC, Watts doesn't equal volts time amps. 
The problem with calulating power consumtion of SMPSUs driven machinery
is that the current hasn't a sin-wave form. You have lots of harmonics
(in addition to the phase shift U => I). Most digital and even analog
meters can't deal with that. So you have to connect a scope to see the
waveform and calculate the integral over i(t) * u(t) dt.
Or simly get a the electromecanical power meter. (Somthing that you
electric power provider uses to bill you.) This meters work different
than "normal" voltage / current meters and don't get confused by
harmonics. 
But simply U * I = P can be a good approximation. ;-)
-- 



tsch,
         Jochen

Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/