Patent ID: 8492167

Claim:
A method comprising: delivering a fluid having first constituents to a surface of a resonant device; monitoring an electrical signal output by the resonant device while the fluid flows relative to the surface, wherein intensity of the electrical signal corresponds to volumetric density of the fluid, viscosity of the fluid, and speed of sound in the fluid; changing the first constituents of the fluid to second constituents while delivering the fluid to the surface of the resonant device, wherein changing from the first constituents to the second constituents change at least one of the volumetric density of the fluid, the viscosity of the fluid, or the speed of sound in the fluid; and analyzing the electrical signal, to determine if the change in the volumetric density, the viscosity, or the speed of sound causes the intensity of the electrical signal output by the resonant device in the presence of the fluid having the second constituents to satisfy a predetermined condition.