Patent ID: 7660681

Claim:
A method comprising: inducing motion in a conduit such that the conduit oscillates in a first mode of vibration and a second mode of vibration, the first mode of vibration having a corresponding first frequency of vibration and the second mode of vibration having a corresponding second frequency of vibration, wherein the conduit contains a fluid; determining the first frequency of vibration; determining the second frequency of vibration; and calculating a density of the fluid based on the first frequency of vibration and the second frequency of vibration using ρ 0 = 1 2 ⁢ ( D 4 + E 4 + 4 ⁢ D 2 ⁢ E 2 ω 1 2 ⁢ ω 2 2 + ( D 4 - E 4 ) 2 ) , where ω 1 is the first frequency, ω 2 is the second frequency, and D 2 , D 4 , E 2 , and E 4 are calibration constants related to physical properties of the conduit.