Wim,
I think we should leave the subject, because we are not coming together as it seems.
When 1/jwC=A+JB, it is mathematically wrong to conclude that jwC=1/jB, because one j is in the numerator and the other j is in the denominator.
Correct is: jwC= IM(1/(A+JB). Solving this leads to wC=B/(A^2+B^2).
And as mentioned, for very small values of A as in serial connections, this becomes the 1/B that FRA Imp Viewer uses.
But after this all, here's a really positive thing that I would like to mention, which is the calibration.
I asked you a few days ago to possibly include the probe's capacity in the calculation, but I found a much better way, making this question completely obsolete.
With FRA4PS I record the chain without a DUT, but of course with the necessary measuring probes in place. Ideally this should give a flat Bode diagram with phase permanently at zero degrees.
Look at the first image below how the Bode diagram looks in my case.
And altough this doesn't look to bad, only 0.06dB and 6 degrees removed from the ideal, the effect of this can be quite massive as we will see.
Now store this Bode diagram as a .csv file, open it in Excel and make a second set with Log Freq, -1*Gain in dB and -1*Phase.
This second set will be your future correction set.
To show the effect, I took a 1x probe as a DUT.
Without any correction, results are shown in the second image.
But when correcting this recording in Excel by adding the gain in dB and phase of the correction set, the now corrected data produces quite a different plot, see the the third image.
So this is way more accurate than just specifying the capacity of the measuring probe.
What you see are resp. Impedance, Resr and two plots for the Capacity, one is using 1/B as in FRA and the second using B/(A^2+B^2), [with A and B being resp. the RE and IM part of Z].
Result is very good after correctio, isn't it.
Hans