On 23/04/2011 05:07, Gerhard Fiedler wrote:
>> This was my point - I'm wondering how accurately they measure the
>> >  instantaneous power.
>> >  For instance, if the power was 10kW for a millisecond then drops to 1=
00W
>> >  for 999ms, but you were only averaging the power over every second th=
en
>> >  you will have a reading of ~110W, and never know about the 10kW peak.
> That's sort of basic measurement theory. The stronger the filter, the
> more stable the reading but you also get less data -- which is the
> objective:)  If you want to see 1 ms peaks, you can't use a 1 s filter
> -- but you'd have to be prepared for the much higher data rate.
>

Yes, it's a very basic point I was trying to make, about just what you=20
mention - getting *less* data. This is not always the objective.
If your concern is about excessive data rates, your have cheap PICs with=20
up to 1Msps ADC capabilities, more than enough for very accurate peaks.
My point is simply what if someone wants to know their maximum=20
instantaneous power attained? For some sports I imagine this may be=20
important/useful to know and it might be good for sports equipment to=20
sample it accurately. For this reason I imagine sampling at a higher=20
rate would be better as it is more flexible - then you can keep the=20
peaks for the true maximums and also average the data in firmware over a=20
longer period. If you filter first the peak data is lost forever.



--=20
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