I'm attempting to find the Q of a clock pendulum while free from the escapement. (crutch and crown removed, so only the spring suspension in use) using the bandwidth method, i.e. Q = "natural" or resonance frequency / FWHPower, no?
I'm driving it E-magnetically using a PM waxed the the edge of the bob (lenticular) and a coil waxed to the case opposite the PM. Not only is this asymmetrical, but also the force is a strong (4th power?) function of the separation (near field). Therefore, I vary the drive to maintain the same amplitude, which is measured by the blocking time of a photogate at ~ BDC, as I manually change the drive frequency in 0.001Hz steps. I assume the drive power is the square of the applied EMF. The undriven frequency agrees w/ the minE drive frequency (~ 5%) [0.565Hz]
So if the min drive E is 0.3V^2 then the diff between the two frequencies at 0.6V^2 is the FWHP, yes??
The result is ~ 1k, which agrees ~ with the ring down method.