Impeadance measurments / OSL calibration algorithm

[sixtimesseven]

Hi

I'm working on a script for the HP3577 to make accurate impeadance measurments over frequency according to this document: http://literature.cdn.keysight.com/litweb/pdf/5990-5902EN.pdf

In particular, I recreated the setup from page 29 (shunt-thru), with the instrument set to HighZ inputs on R and A (same as R and T as laid out in the Keysight document above).
The measurements I get from my python script seem are fairly accurate without cal, however, I would like to do open / short / load calibration as the document states.

By performing the
3-term calibration (OPEN/SHORT/
LOAD calibration) in the impedance
domain, the measurement system is
fully adjusted at the measurement

I found some information on the calibration methods used when doing vna s-parameter measurements. But I could not find anything specific to impedance measurements. So I would love to be pointed to a reference to read up on the topic.

So far I came up with this. In the ideal case the measurements should be:

If the DUT is open: Vt ~ Vr ~Usource (because the input impedance of R and T >> Ri and >> 50Ohms)
If the DUT is short: Vt = 0 and Vr = Usource * Ri / (50+Ri)
If the DUT is loaded with Rload: Vt = Usource * Rload / (Rload + Ri + 50) and VR = Usource * (Ri + Rload) / (Ri + Rload + 50)

This looks like some sort of optimization problem to me...(?)
 
In addition I would first have to measure the Ri(f) and Rload(f) of course to get rid of that error as well. However the Usource might still vary and introduce an error.

As I said, any sources or documents or other inputs would be appreciated.
Thanks a lot!




EDIT:
- Apparently it is called OSL calibration
- The usual spelling mistakes


UPDATE:
- Following papers on the topic are rather helpful:

• http://www.hpl.hp.com/hpjournal/94oct/oct94a12.pdf
  
• http://kripton2035.free.fr/Resources/Impedance%20Measurement%20Basic.pdf
  

[sixtimesseven]

Well seems I was to quick to pose this question. Found this nice document after a lot more googling:

http://www.hpl.hp.com/hpjournal/94oct/oct94a12.pdf

... If I just had known for what to search for...

Anyway, my code attached. Seems to give reasonable somewhat believable results 
Now I have to measure my Load impedance and maybe build a second capacitive load as described in the document above. And I have to go over the code again some more - This is still wip and I'm also very tiered so use with care.

All the relevant code I used so far is attached.
Current code GitHub: https://github.com/sixtemesseven/visa-instruments

[bson]

Why not use the full OSL cal built in to the 3577?  That's what I do...

[sixtimesseven]

Why not use the full OSL cal built in to the 3577?  That's what I do...

Several reasons really:

• I like to have to have a script which I can run and document measurements without having to setup the instrument manually every time.
• Correct me if I'm wrong but I do not see how to input corrected impermanence over frequency values for the OLS standards
• Possibility to implement other measurement schemes than implemented by HP originally