[ntp:questions] Re: announce: NTP FAQ v3.8

Ulrich Windl Ulrich.Windl at RZ.Uni-Regensburg.DE
Wed Jan 26 14:51:28 UTC 2005


"David J Taylor" <david-taylor at invalid.com> writes:

> Ulrich Windl wrote:
> > Alain <alainm at pobox.com> writes:
> >
> >> Some questions:
> >>
> >> - in Section 3.3 it says: "Some of the best clocks available still
> >> have errors of about 1E-8 PPM" Is this really 1E-14 ?
> >
> > 1E-8 Parts per Million are 1E-14 parts. Right?
> >
> > Like 1E-1cm is 1E-3m.
> >
> > Regards,
> > Ulrich
> 
> Mixing numbers like that is very confusing.  My personal feelings are that 

Isn't "PPM" wrong per se? Shouldn't it be micropart (µP)? ;-)
Wo we easily could have milliparts and nanoparts...

> if you use PPM, then the units should be whole numbers: 15 PPM,  2 PPM 
> etc, certainly /not/ fractional parts.  If you must use fractions, then 
> not more than one decimal place - 1.6 PPM, 0.3 PPM  If you need to express 
> smaller quantities, just stick with scientific notation 1E-12,  1E-14 etc. 
> Clarity of communication is very important.
> 
> Even better, of course, where you can use superscripts to write 10-12, 
> 10-14 (but not in this plain text e-mail!).

OK, I'll try to keep in mind.

Ulrich

> 
> Cheers,
> David 



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