I have been tasked to verify the input impedance of a medium powered DC/DC converter (<1kW), and no experienced colleagues to consult on the matter. I have quite a good description of the required test setup, including the choice of isolation transformer for coupling in the AC pertubation, current and voltage probes. I'm intentionally holding back on the details here for anonymity reasons, so apologies for that.
It is clear, that I need to exercise caution not to saturate the transformer core at low frequencies and keep a close eye on the primary and secondary levels.
What is missing, however, is the description of the power source, and this is where the uncertainty starts. Looking at the setup, I assume there's no way the source output capacitance isn't going to influence the measurements of the input impedance at the input of the converter.
The question is what calibration method to use for the VNA in order to compensate for the excess capacitance of the source. The VNA/FRA available is generic, and will dump the voltage magnitude/phase it sees at its inputs, and is not guiding the user through any calibration procedure.
How, oh wise masters, would you proceed in order to get a trustworthy measurement?