Patent ID: 8196451

Claim:
A detection sensor comprising: a disk-shaped resonator having a vibration characteristic changed by adherence or adsorption of a substance having a mass; a driving unit that causes vibration of the resonator; and a detection unit that detects a change in vibration of the resonator to detect the substance, wherein the resonator having a ring shape with an outer diameter Ra and an inner diameter Rb with an opening formed at the center; the resonator being formed of the outer diameter Ra and the inner diameter Rb that substantially satisfy U(r)=0 or V(r)=0 when r=Ra or Rb for displacement U(r) in a radial displacement and displacement V(r) in a tangential direction expressed by Expression (19) in a position r on a position coordinate (r, θ) when the resonator vibrates; and the resonator is supported on an anchor by a single-span beam set so that a boundary condition on a side of the resonator is pinned and a boundary condition on a side of the anchor that supports the resonator is clamped, where Expression 19 is expressed as: U ⁡ ( r ) = ∂ ∂ r ⁢ J n ⁡ ( hr ) + A 6 ⁢ n r ⁢ J n ⁡ ( kr ) + A 7 ⁢ ∂ ∂ r ⁢ Y n ⁡ ( hr ) + A 8 ⁢ n r ⁢ Y n ⁡ ( kr ) ⁢ ⁢ V ⁡ ( r ) = n r ⁢ J n ⁡ ( hr ) + A 6 ⁢ ∂ ∂ r ⁢ J n ⁡ ( kr ) + A 7 ⁢ n r ⁢ Y n ⁡ ( hr ) + A 8 ⁢ ∂ ∂ r ⁢ Y n ⁡ ( kr ) ( 19 ) where h = ω ⁢ ρ ⁡ ( 1 - σ 2 ) E , k = ω ⁢ ρ ⁡ ( 2 + 2 ⁢ σ ) E , k = h ⁢ 2 1 - σ , ⁢ and where σ represents Poisson's ratio of a resonator material, E represents Young's modulus of the resonator material, ρ represents a density of the resonator material, ω represents angular frequency, n represents a degree of vibration mode, and A 6 , A 7 and A 8 are constants uniquely determined by natural vibration mode specified by outer diameter and inner diameter of resonator, Young's modulus, density and Poisson's ratio of resonator material, and the boundary condition (in this case, free-free condition) of the resonator, wherein the single-span beam has a length and a width set so that a vibration frequency thereof is substantially equal to a vibration frequency of the resonator.