Importance

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Abstract

A vibratory force transducer comprising a vibratory beam (21) of rectangular transverse cross section having a uniform thickness t, a major span section of length L.sub.1 and width w.sub.1, and at least one end of the major span having an adjoining tab of greater width W.sub.2 and length L.sub.s. The beam is driven by electrical excitation to vibrate at resonant frequency in a given direction. The tab provides the beam with an effective length which is a function of length of the beam sections and their moments of inertia in the given direction and a criterion by which t, w.sub.1, L.sub.1 and L.sub.s are selected such that resonant frequency and higher harmonic modes of the beam in the given direction are different from the resonant frequency and higher harmonics in any other direction. The transducer may comprise dual beams (31,32) as a double-ended tuning fork with moment decoupling number (45) at the joined end. For each beam comprising a major span of length L.sub.1 and adjoining tab, an effective length is determinable using L.sub.1, L.sub. s and moments of inertia in a given direction of vibration as a criterion by which t, w.sub.1, L.sub.1 and L.sub.s are selected to avoid spurious out-of-phase oscillation in other directions. An effective length for a length L.sub.3 of the transducer which includes the decoupling member is determinable from L.sub.1, L.sub.s and L.sub.3 and moments of inertia as a criterion for selection of t, w.sub.1, W.sub.2, L.sub.1 and L.sub.s for avoiding spurious in-phase vibration perpendicular to the given direction.

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First Claim