Abstract
Viscosity sensors based on mechanical resonance, such as piezoelectric resonators, semiconductor resonators, vibrating wire resonators and our previously developed optical-fiber based resonator [1] have gained popularity due to their simplicity of design and operation. They detect viscosity by submerging an oscillating probe in the fluid of interest. Viscosity is measured by using the fact that the vibration amplitude of the probe is inversely proportional to the viscosity of the fluid. In practice, the vibration amplitudes are always kept sufficiently small in order to avoid nonlinear vibration effects. In this paper, however, nonlinear vibration is intentionally excited to improve the sensitivity of viscosity measurements, in particular super harmonic resonance case. The results show that a nonlinear effect drastically improves sensitivity to viscous damping. Experimental results and several applications are also presented. © 2013 SPIE.