Patent ID: 6789053
Filing Date: 2004-09-07
Classification: G01P

Abstract:
A method for designing double-ended tuning fork (DETF) sensors such that the second-order non-linearity of a first DETF and of a second DETF substantially cancel, the method comprising the steps of:a. designing said first and said second DETF using finite-element methods, said design including nominal no-load frequencies and scale factors, and said DETFs having substantially equal second-order non-linearity terms; b. creating a finite-element model, said finite-element model including at least: said first DETF, said second DETF having at least one mass balance formed thereon, a movable structure, a fixed support structure, at least one hinge member rotatably connecting said movable structure to said fixed structure, and said first and second DETFs spaced apart and connected between said movable structure and said fixed structure; c. within said finite-element model, applying forces to said movable structure to cause said movable structure to rotate about said hinge member and applying full-scale force loadings directly to said DETFs; d. within said finite-element model, said DETFs being in a deformed, pre-stressed state, using non-linear analysis to find a vibration frequency F1 of said first DETF and a vibration frequency F2 of said second DETF; e. repeating step (d) for a plurality of different forces, said forces being between a negative full-scale force and a positive full-scale force; f. using curve-fitting techniques to find the non-linearity in the difference frequency, where said difference frequency equals F1âˆ’F2; g. repeating steps c, d, e and f for a plurality of mass balance configurations; h. creating a model of second order non-linearity as a function of said mass balance configurations; and i. selecting said mass balance configurations such that said difference frequency is a minimum.