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Re: [Phys-l] glassware needed



At 07:49 PM 1/1/2009, Ludwik, you wrote:

For fluctuating values of P, E=SIGMA[P(t)*dt]. How high should the
sampling rate be? For a randomly fluctuating I(t) the sampling rate
does not have to be very high. ...
3) An electric arc (for example between welding electrodes in salty
water) will produce a rapidly fluctuating current. ...
Ludwik Kowalski,

While it is is easy to sample a waveform like the alternating current
that has been chopped by an SCR or triac dimmer by using
dozens to hundreds of samples per cycle, Ludwik points to an
experimental feature that seems to have tripped more than
one cold fusion experiment:
calorimetry with heating provided by wildly fluctuating
current spikes.
This sampling arrangement faces the usual Nyquist criterion:
at least a coupla samples at the highest frequency of interest.

If the heating waveform includes one microsecond long
current spikes, then sampling at megahertz rates would be
involved to catch the heating spikes that otherwise contribute
"Excess power production".


Brian Whatcott Altus OK Eureka!