Linear Variable Differential Transformer (LVDT) & Coefficient of Coupling

Howdy folks. I've been playing around with the idea of doing a video on LVDT's for a while now. I finally have the lock-in amplifier repaired, needed to measure the phase shift, so we're go for launch. I take a ball point pen and wind some coils around it (with the microprocessor controlled coil winder, a few vids back), use a ferrite core mounted on the ink shaft and it works like a charm. I also cover how to measure the coefficient of coupling with my crappy LCR meter. Worked out ok. Anyway, I hope you guys learn something or can use and LVDT for one of your projects. If you do, let me know. I'd love to hear about it!!!