I do not want to drag in dirty laundry from other forums, but here is an
interesting summary of Shanahan's views, from Forbes. I do not think he
wants to participate here, so I'll copy this message, and my response.
In the following intro I am NOT denigrating Shanahan. It may sound like it,
but I am not.
This discussion illustrates a profound, fundamental difference between him
and me. He believes in looking for errors by thinking or theorizing,
whereas I believe in looking for them by hands-on tests. By calibrating,
and comparing instrument readings.
I distrust theory. Shanahan distrusts direct observations and hands-on
techniques. He suspects that IR cameras do not function the way the
manufacturers' claim. He wants to get back to first principles and prove to
himself that the IR camera is or is not working, whereas once I see that it
agrees with the thermocouple, I couldn't care less about the theory of
operation. If the thing shows the right temperature it could be working by
magic pixies for all I care. Both approaches have their strengths and
weaknesses.
This difference goes back centuries to the philosophies of France and
England, specifically Descartes versus Francis Bacon, and later to the
British empirical philosophies of Hume, Locke and Berkeley. Even today, you
will see that French philosophy, engineering, social planning and so on
tends toward idealism (in the technical sense) while British methods tend
to empiricism and pragmatism. You can see expression of this in things like
the design of the London Underground (subway) and the Paris subway. In the
U.S. our subway systems resemble those of England because our intellectual
traditions are British.
- Jed
- Kirk Shanahan http://blogs.forbes.com/people/kirkshanahan/4 hours
ago
For those who are following this debate, Jed, the King of Misdirection,
is at it again. He says he wants to summarize my position, but actually
summarizes his strawmen and mischaracterizations.
What I have said, in summary is:
- The temperature measurement device used is rarely used for absolute
temperature determination such as is used in calorimetry (because…(see
following))
- The likelihood that the Ecat is a perfect Planck radiator is small (we
know this from the pictures)
- The power computation used is based on Planck’s blackbody equation
- Thus the power computation has some error implicit in it, which needs
to be defined
- You need the Ecat spectral radiance curve to do that
- Because the Ecat is probably not a perfect Planck blackbody, the
temperatures determined from the camera are probably not absolutely correct
- Additionally, the geometry of the Ecat-camera setup does not fit a
point-source radiator, which is what the Planck-derived power equation
assumes, i.e. another implicit error
- The paper reports some comparison to a thermocouple was done, but
summarizes it down to a single number. This is not acceptable practice for
a paper that supposedly will revolutionize physics as we know it
Also
- Levi used 723K in his power computation while reporting 709-711K
depending on how he divvied up the viewed area, which produces a 100W error
in radiated output power which needs to be explained
- The convective power term depends on the temp too, so it will be wrong
too if the T is off
- Without having examined it in detail, I suspect the convective power
calculation may have as many built in, unmet assumptions as the radiative
computation
Please look over what I said and compare to what Jed says I said, and
then decide if you can trust Jed to give you the straight scoop…
- [image: jedrothwell] http://blogs.forbes.com/people/jedrothwell/
jedrothwell http://blogs.forbes.com/people/jedrothwell/1 hour ago
Shanahan wrote: “- Thus the power computation has some error implicit in
it, which needs to be defined.”
No, the error needs to be measured. It was measured, by comparing the
temperature detected with a thermocouple to the temperature detected with
the IR camera. They were the same to within 2 deg C. They remained the same
throughout the test. There is no chance that both instruments were wrong
and yet they both showed the same temperature. Therefore all of this
verbiage from Shanahan is nonsense.
You do not compute errors. You do not wave your hand and theorize that
there might be errors. You check for them. You calibrate your instruments.
By the way, they also calibrated the thermocouple with ice slurry and
boiling water, which is the standard technique.
Despite what Shanahan believes, IR cameras in the hands of experts do
work according to the manufacturers’ specifications. These seven experts
followed instructions, measuring emissivity and comparing the output to
another instrument. They did everything by the book. There are no better
methods or methods of calibrating or cross-checking
