IEC 61788-4-2020 pdf free download

IEC 61788-4-2020 pdf free download.Superconductivity Part 4 Residual resistance ratio measurement – Residual resistance ratio of Nb-Ti and NbaSn composite superconductors
Supraconductivity Partie 4 : Mesurage du rapport de resistance residuelle-Rapport de resistance residuelle des composites supraconducteurs de Nb-Ti et de Nb2Sn.
b ) Measurement of voltage vs time
Instead of measuring the voltage as a function of temperature , one can determine the
cryogenic resistance from a voltage-versus-time curve that is continuously recorded both
below and above the transition . Care should be taken not to re-cool the specimen without
re-starting the acquisition of voltage-versus-time . The characteristic voltages , such as
can be similarly obtained from the intersection of the two straight lines drawn on the region
of steepest slope during the transition and on the relatively flat region sufficiently above the
transition in the voltage-versus-time curve . The analysis afterward to determine the
cryogenic resistance is the same as in the reference method
C ) Fixed temperature method
In this method R2 or R2 is directly determined at a fixed temperature in a plateau region
within about 4 K above the transition for Nb-Ti composite superconductors , and R , is
directly determined at 20 K for Nb3Sn composite superconductors , instead of using the
method described in 7 . 2 . In this case it is desirable to check that the whole specimen is at
a uniform and fixed temperature . In the measurement of Nba Sn composite superconductor
the fixed temperature of 20 K should be determined with a combined standard uncertainty
not exceeding 0 , 6 K . The fixed temperature and the combined standard uncertainty should
e noted in the test report . Also the Un . and U , which are defined in 7.2.2 , should be
recorded as the zero voltage level in the fixed temperature method . In order to eliminate the
influence of thermoelectric voltage , two voltage signals of the specimen , say U , , and U2
should be acquired nearly simultaneously by reversal of the test current . For the fixed
temperature method the effect of thermoelectric voltage on determination of cryogenic
resistance can be eliminated
d ) Computer-based method
A computer can be used to control the current direction and warming of the specimen and
to measure the voltage-temperature curve . Changes in current direction by periodic current
reversals or periodic current on and off cycles are used to correct for offset voltages in order
that the measurements can be made during one cycle of changing the specimen temperature
The effect of thermoelectric voltage should also be checked.IEC 61788-4-2020 pdf free download.