On Sun, 19 Feb 2006 12:52:26 -0500, John Popelish
wrote:

Boonton originally sold Q standard coils (inductors with known Q) to
be used to check the accuracy of the Q meters. I don't know how those
coils calibration got back to basic measurements traced to the Bureau
of standards.


Hi John,

And for the sake of trolling, Reggie claims he doesn't either.

Gads this is so simple as to defy the angst that surrounds this. Any
good Impedance Bridge which reports R and X separately will give you
the means to measure the Q (or D) of these standards. All this
folderol of the "Q quality of the meter" is so much hokum distracting
from a simple determination.

Balance the bridge and you will have the resistance that so impacts
the Q. Balance the bridge and you will have the reactance that
establishes the Q in relation to the resistive loss. And what does
the meter have to do with Q? The bridge is adjusted for a zero
reading! What accuracy statement can be said about reading zero when
you return the needle to the position it was in when the unit was
stone cold? THIS is how you qualify the standards Boonton offers. You
then qualify your Bridge against separable quantities of X and R.
For sure, this may relegate us to a tedious cascade of "how do you
know what value those are really?" It is this kind of whining that
leads to warning statements being forced into curriculums by those who
want to teach Untelligent Design.

Reggie has managed to turn the discussion of Q into a mystical,
unknown quantity impossible to determine by his simply ignoring first
principles. You measure the Q of the unknown two ways and compare. By
the Bridge and by the Boonton. I dare say no more than 20%
accumulated error will occur with NONE of it attributed to the "Q
quality of the meter" - whatever that is.

So, let's compare. You can have a determination within 20% of actual,
and continue to design with confidence. OR You can mumble about the
abstract impossibility of ever getting it abso-*&!#ing-lutely right
and find yourself in analysis paralysis.

I have, of course, steeply discounted the accuracy of the Boonton to
include all RSS accumulation of errors in the instrument's
calibration. The manufacturer warrants the device to 5%.

Now, if you strip away all the numbers, you can re-achieve the
distinction of the Qualitative statement that got us here. Lord
Kelvinator would point out that that and $5 will buy you an insolated
cup of Laté.

73's
Richard Clark, KB7QHC