At 01:00 AM 12/13/2012, Eric Walker wrote:
I wrote:
Re almost hourly fluctuations in T_Ambient -- the HVAC system
kicking in periodically, maybe?
Also, do any of the electronics folks here know what the effect
might be on the instrumentation providing us with a measure for P_in
if the external power supply were erratic?
Power supply monitoring is essential. The usual suspected problem is
the presence of transients that would cause error in voltage or
current measurements, or, even if those are done in a way that
produces correct averages, the power with complex signals can differ
from the product of average current and average voltage.
So workers look at the power supply voltage/current with
high-bandwidth oscilloscopes, and use power calculations that are not
naive. For example, the voltage and current may be sampled
simultaneously at high data rate, and multiplied to calculate
instantaneous power, and then *that* is averaged and reported
periodically, as every second or every minute.
I've seen attempts to criticize the SRI results based on claims that
the input power was not accurately measured. That is Garwin's last
stated opinion, by the way, that there "must be some error." Looking
at the overall data, it's preposterous, but this kind of claim can be
made, armchair, by those who concluded long ago that it wasn't
necessary to get into the details. Since cold fusion is "impossible,"
of course.
Dieter Britz also, recently, at the suggestion of a skeptic with whom
I was engaged in extensive discussions, examined the issue. Bubble
noise causes transients in power supply voltage, and Britz looked at
the actual effect, based on known experimental data from the past. He
found that any possible error was insignificant.
But caution is needed, obviously, and naive beginners in the field
might miss some of these possibilities.
