So what exactly is needed to make this graph?

[Possum]

...

I tried my method again with a strat bridge coil with iron loading, and get a defined peak at 9.2khz and rapid drop off from there. If oscilloscopes read voltage over time wouldn't what I'm doing be a valid method? Driving a coil with a low impedance driver coil and measuring the AC voltage coming out of the pickup? What could be simpler?

[Joe Gwinn]

Doesn't the Extech measure AC resistance?

Yes, exactly. Nor is the Extech even able to measure DC resistance.