Re: Canadian Prices (Frank Sprongl)

[Glenn Lawton <lawtonglenn@gsmai.com>]

Robert Myers wrote:
> ...Back when I usta grade stoont lab reports (otherwise known as
> science fiction) these calculation results would be marked -2 each as sig.
> fig. errors.  :-)
> 
> >
> >Please pardon the unneccessary precision, but back from my days
> >as an optics engineer, when such precision mattered:
> >
> > 1 m   =       39.37007800 in


Thanks for the :-), as I know you are only poking me in a playful way,
and I already pre apologized for the unneccessary precision, but these
insignificant figure are sometimes significant, for example:

If my drawing said that the lens or mirror I was making had one feature
that was 0.1 meter from another, and I told my diamond turning machine to 
move 3.937000 (it has 1 micro inch resolution), then it would be
in the wrong place by 7.8 microinches.

Since we regularly used HeNe (632.8nm) laser interferometers to measure
how accurately we made a part, and often had to meet figure tolerances
of 1/4 wave, and since 632.8nm/4 = 6.2 microinches, 7.8 is too much! :-)

Glenn