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If one sweep frequency drives harmonically with constant amplitude a linear** oscillator, the amplitude response width (down 1/sqrt2) will reveal it's Q. [Q = resonance freq. / width at 0.707 etc.]It is not conservative to suppose that input power to a solenoid is proportional to the square of input voltage amplitude, where the drive voltage varies in frequency.
I've such driven pendula of varying Q.*** Unfortunately, I used an electromagnetic drive whose force varies considerably with distance. (dipole coil and magnet). Therefore, I varied the drive power to maintain a constant pendulum amplitude. A result is here:
Pendulum response to E-M harmonic drive.tiff 1352×706 pixels
The Qs were found by fitting the free decay to an exponential. I wish to compare the response width to my free decay Q values. How does one do this? The power values are the square of the drive EMFs (for constant pendulum amplitude) The screen shot includes one of the trial's data plus the values for the Q(bob mass) graph.
** n.b. used very small amplitude (~0.44radian; rotary motion sensor resolution ~ 10%!)
*** by changing the bob mass -- The pendula's magnets were immersed in a water in order to reduce all the Qs for convenience. This was because my function generator has very poor resolution, and, with low Q, equilibrium and decay are obtained quickly.
Soon I intend to post a more complete description including pictures of the apparatus, etc.
bc