This report presents a methodology to measure transducers using a dual-added-mass technique in order to extract the motional impedance ZM(w) and force factor Bl from the total impedance. The method is more accurate than the classical single-added-mass approach insofar as the blocked electrical impedance can be completely filtered out of the total impedance. The methodology is suitable for determining moving mass and compliance in motional impedance models that include viscoelasticity and frequency-dependent damping. It is applicable to transducers for which adding mass to the moving parts is possible without introducing significant artifacts. A mass-consistency test is described to provide an internal validity check for the impedance fitting process. This test is quite stringent and provides an objective measure of the quality of the fit to the measured impedance. The quality of the proposed measurement technique was verified with an ANOVA Gage R&R measurement system analysis.
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