At 04:34 PM 18/04/2011, you wrote:
>On 18/04/2011 20:41, RussellMc wrote:
> >>> However, in many cases power is
> >>> averaged over a number of seconds with the display being updated
> >>> periodically, so short term variations are smoothed out.
> >> Yes - specifically stuff like the above, was exactly what I was
> >> wondering about.
> >> So in this case the 10kW for a millisecond example I gave in my other
> >> mail would not be "noticed".
> > It would be noticed as a contribution to mean energy in.
>
>Yes - that's why I put the noticed in brackets :-)
>I meant that peak specifically would not be noticed, although of course
>it's energy will contribute to the reading.
>
> > Reading too finely can cause problems.
> > When pedalling a bike the power is delivered in two surges per crank cy=
cle.
> > If you track this power variation and display it, a digital display
> > would be a constant mess of changing figures. Even reading an analog
> > display would be difficult if it tracked power surges.
> >
> > At one stage I had a certain update rate - maybe once per second, and
> > customers asked for a much slower update rate.
>
>I was thinking more along the lines of a setting to choose how the
>information is gathered. I guess normally people will want to know the
>average power over a while, so the slow update/sampling will not be an
>issue. If you want to know peak instantaneous power it is though, so
>maybe you could read at a higher rate, but display at a slower rate,
>while retaining things like maximum peak power/speed attained.
>You could even have a graph of power over time in more advanced machines.

I would average the power over an integral number of rotations of the
crank, with a minimum and maybe maximum update rate. You _know_ it's
going to vary cyclically, and the update rate does not have to be fixed,
so why not take advantage of this degree of freedom?

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the rewar=
d"
speff@interlog.com             Info for manufacturers: http://www.trexon.co=
m
Embedded software/hardware/analog  Info for designers:  http://www.speff.co=
m



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