Possibly a silly question, but have any Q meters been built that use
the other approach of watching the relaxation decay starting with a
forced excitation and calculating the dissipation factor?? Most of
the inductors I'm working with at LF/VLF have a Q of 300 or more, so
would it be feasible to resonate one with a very high performance
capacitor, tune a power oscillator to the resonance peak
automatically, then disconnect it at a zero crossing and capture the
decaying oscillation with a fast high impedance ADC and process it
to determine the Q based on the envelope decay?? Indeed, would a
single voltage or current pulse suffice as the excitation rather
than an oscillator? A quick simulation suggests that it is feasible.
With a resonance at 150 kHz and a Q of 300, the envelope amplitude
falls to about exp(-pi), around 4%, after 2 ms, or 300 cycles, which
is another way to define Q factor.
