The pie charts that Anders created show clocks in the UTC "flywheel".
That excludes most research fountains and optical clocks because they
can't or aren't run continuously.
Of the 427 clocks [1] in that data set there are 247 5071A (58%) and 167
H-masers (39%) and 6 fountains (<1.4%). So the short answer to your
question is that there are only 6 fountains in the chart: 4 Rb fountains
at USNO and 2 Cs fountains at PTB.
When playing with charts, it's important not to confuse the number of
clocks with the weighting of clocks. And even the weighting is
misleading because for practical reasons any clock's weight in UTC is
capped at about 1%. All 4 of USNO's Rb fountains are at this level, for
example. About 60 of the H-masers are also at this level. And none of
the 5071A; not even close.
If you are a 5071A sales person you are likely to emphasize that 60% of
the clocks in UTC are 5071A. You are less likely to mention they
contribute only 8% of the weight these days.
If you are in H-maser sales you can claim 40% of the clocks in UTC are
masers and also they contribute 88% of the weight.
It's a good time to be in Microchip clock sales: they now own both the
hp 5071A and the Sigma Tau H-maser manufacturing plants. Yes, they still
make PIC chips too ;-)
/tvb
[1] https://webtai.bipm.org/database/clock.html
- clock type 35/36 are 5071A
- clock type 40/41 are H-masers
- clock type 92/93 are Cs/Rb fountain
On 3/28/2021 6:15 AM, Bob kb8tq wrote:
Hi
I would *guess* that fountains would be in there somewhere ( at least in the
2021 version ).
Bob
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