I guess your Y-axis mean all ppm values are related to 10V. Is that right?
Yes, that's ppm full scale so in that case 10V. I think in the next revision we should be collecting sdev as well to have error bars.
The calculating script has rather unfortunate naming, because the values from the calibrator (5720A or 5440B) are called 'ideal', while 3458A measurments are called 'real', but in reality I treat 3458A as ideal (in absence of a JJA
) and calculate the calibrators INL. Probably adding sdev and doing some root sum squares with 3458A INL specs (AFAIR 0.05ppm) could improve the calibrators' INL estimates.
Suggestions for more mathematically sound calculations are very welcome!