On 3/26/21 6:52 PM, Richard (Rick) Karlquist wrote:
At HP, it was explained that a primary standard
could be built on a desert island containing no
frequency standards nor any GPS receivers, etc.
and it would be guaranteed by design to meet its
spec. It could have adjustments, either operated
by a technician or a computer controlled algorithm,
but none of them consisted of "setting" the frequency
to the correct value using a frequency counter, etc.
It isn't based on accuracy. The reduced performance
HP 5062 is still primary, even though the 5061 is more
accurate. Similarly, the 5071 is still more accurate,
but the 61 and 62 retain their primary status.
ADEV is not an issue to qualify for primary status.
Would a sundial (or zenith meridian crossing sensor) be a primary
standard for measurement of a solar day?
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