Normal chip measurements are with a 3 point probe, the probes are like coax, center conductor and two outer grounds, but it's just 3 points. Needs an expensive analyzer and a good calibration kit with data.
The old fashion method of reflectometer measurements can get you magnitude but not comples.
Probably a calcualation is better if you have dimensions.
If it's real low frequency, just an LCR meter would give you something.