Great, suppose the synthesizer that generates the pumping
frequency from the stable frequency standard is malfunctioning,
and producing a frequency off from the 483597.9 GHz/V that
defines the JJA volt? Say it is providing 483597.902 GHz?
Or, suppose that for some failure, one of the two leads that
is transporting voltage out of the cryogenic section is finding
itself at a different temperature than the other?
Or suppose the terminals you are using to connect to the outside
world have developed a difference in the alloy that connects
them to the DUT?
Without a pair of references you cannot tell if such a failure
exists.. Without at least 3 such references, you can't tell
which is the misbehaving reference.
-Chuck Harris
Joe Hobart wrote:
Thanks to the DOD and radio waves, accurate frequency is available at most
places on Earth. SPRTs and more robust Reference PRTs have been available for
many years.
Frequency to one part in a thousand million is easy. Measuring temperature to
0.1 degree C is also easy; controlling temperature may not be as easy.
What are the frequency, temperature, and other requirements for the
"inexpensive" JVS systems NIST has been developing?
How many similar JVS/JJA units does a major test equipment company like Agilent
or Fluke have at any one location?
Joe
On 2/16/2014 12:00 PM, Chuck Harris wrote:
There are a host of things that will cause a JJA to be
off voltage... not the least of which is temperature and
frequency.
Absent other standards to compare with your JJA, you are
really operating in the blind.
The only major advantage to the JJA, and the reason it is
given primary standard status, is it relates voltage, to
frequency. If the pumping frequency is offset for some
reason, the voltage will be wrong by a similar amount.
Do you imagine that NIST uses only one JJA to hold the
nation's standard volt?
-Chuck Harris
_______________________________________________
volt-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
