[volt-nuts] What made a HP3458A so expensive
cfharris at erols.com
Sat Jan 18 22:12:25 EST 2014
Of course you would need to calibrate a JJ standard. If you recall,
the JJ works by being cooled to some LN2 like temperature, and then
being fed with a microwave frequency that is part of the standard's
definition. If the temperature is wrong, or the frequency is wrong,
or ..., the voltage will be wrong. The whole point behind the JJ is
that it connects the standard voltage to the standard frequency/time
... the most accurately specified of the known standards.
Cs standards, even though they are primary standards, are also in need
of calibration because the frequency they create is dependent on the
magnetic field surrounding the tube, and the construction of the tube.
All Josephson Junction V standards produce a slightly different voltage,
and all Cs standards produce a slightly different frequency.
Joe Hobart wrote:
> Would a Josephson Junction standard need to be calibrated?
> Adjusted and maybe compared, yes, but you should not need to calibrate a primary
> standard? Years ago we had HP Cesium Frequency Standards at work. There were
> primary standards and good to 4E-12 with no additional calibration.
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