[time-nuts] Primary standard again

[WarrenS]

The time nut post is still discvarding my rants, BUT I do not give up easy, ONE more try to trick it and get it all in.

Rick

Thanks, Interesting but maybe you have missed my too subtle of a point.

Example:
Lets say the second is redefined in the future to some new super duper thing that is good to 1 part in e20
(Which will happen  if (when) the super duper thing becomes more available and proven)
(Maybe based on the time it takes to count all the atoms in the new purposed 1 Kg sphere OR something like that.)

Then the CS Osc would not be the BEST primary standard anymore, at least NOT at the new improved spec it could then be given.
Not because it has changed or is less accurate, but because there is now something better.
If it is not the primary standard, it does not make it worse, 
but it does mean it will now be a second standard at the new higher performance spec, by definition and need to be then calibrated and checked against the new primary standard IF one wanted to use it to it's maximum capability as a cost effective substitute for the supper duper.

Same with RB,  One can not do something to it to make it  more than say 1 part in e6 (or whatever) that the cave man needed, so it could of been their Primary repeatable Intrinsic standard that was repeatable Good Enough without cal for them.


    ** Primary means that the clock will meet its spec without being "calibrated" against a better clock**

    From your definition a Rb can be a primary standard for a 1e-6 world and a crystal as well as my wrist watch 
can be a primary standard in a 1e-3 spec or whatever  they can repeat without Calibration.
BUT I have not heard anyone argue that any of the above are primary standards, even at some reduced spec. 
(maybe just because not cost effective?)

The existing Cs oscillators can not be primary standard at the new 1e-16 + accurate word, 
but they would be useful just the same in that word as a secondary standard.

There is always progress and change in the time world
ws

**************************************
ws

Sorry but you have completely misunderstood the concept.
It is admittedly a difficult concept to grasp; I know it took
me a long time.

A hydrogen maser with the wall shift servo'ed out will run rings
around a compact Cs beam clock like the HP5062, used on submarines.
(An interesting trivia item is that I don't believe the 5061 can
fit through a submarine hatch).  The 5062 is still a primary
frequency standard and the hydrogen maser is still a secondary
frequency standard.

Regarding "drift" of primary cesium beam standards:  the 5071A has
unmeasurable drift, aging and tempco, down to a measurement limit
of at least 1E-15.  It has a typical *random* error of a few parts
in 1E-13.  The systematic error (average error of all 5071A's built)
has been established to be below 1E-14.  It will always be a
primary standard even in the presence of longer reversible optically pumped
laboratory Cs beam standards of higher accuracy and better short term
stability, or cesium fountains, etc.  Even the 5061A/B is considered
a primary standard, albeit with reduced accuracy, even though it
has a measurable tempco.  We were very proud of the E1938A crystal
oscillator when it was able to meet the 5061 tempco spec.  It
is in no way a primary frequency standard regardless of that
or any other accomplishment.

Primary means that the clock will meet its spec without being
"calibrated" against a better clock.  Secondary means that
calibration against a primary standard is necessary.

Rick Karlquist N6RK


******************

******************
WarrenS wrote:
> All very informative and useful information for sure and good to know,
> But I'm thinking the real difference between a primary and secondary
> standard,
> Has More to do with if there is anything else more accurate and repeatable
> available.
> I'd guess a Rb would of made a great cave man Primary standard.
> And sounds like it will NOT be long before the Freq and drift of a CS
> Primary will be consider just another secondary standard that will have to
> be calibrated.
> (to get the 1e-16 + or whatever accuracy/repeatability  it is they are now
> working on.)
>