| 摘要 |
A system for measuring damping and that includes an oscillator that produces an excitation signal for a resonator that can be placed in a damping medium. A sensor produces a sensor signal responsive to resonator motion. Also, a timing circuit ensures that excitation and sensing occur during mutually exclusive periods. An amplifier responds to the sensor signal, producing an amplified sensor signal. A phase detector is adapted to measure the phase relationship between the excitation signal and the amplified sensor signal and a controller is responsive to the phase detector to adjust the excitation frequency of the excitation signal, to create a phase lock loop. An integrator receives the amplified signal during periods that are mutually exclusive to and interleaved with the excitation. This integrator produces an integrated DC and low frequency component of the amplified signal, which is subtracted from the input amplifier input.
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