Resonant sensor assembly

Abstract

A triple beam resonator (10) is provided with three beams or tines (12, 14, 16) aligned in parallel alongside each other and joined at a decoupling zone (18) at each end, which is in turn connected to the surrounding material. The central beam (14) is twice the width of the two outer beams (12, 16). The resonating element has a length of 15.5 mm, a thickness of 0.25 mm and beam widths of 2 mm and 1 mm. The distance between the beams is 0.5 mm. Finite element analysis predicts the modal behaviour with stress distribution and eigenfrequencies of the resonator (10). Thick-film PZT elements (20, 22) were printed on separate regions at each end of the central beam (14), where maximum stresses exist as the resonator (10) operates in its favoured mode of vibration. The PZT element (20) at one end drives the vibrations, while the PZT element (22) at the other end detects them. Positioning the PZT driving and sensing elements (20, 22) on the regions of maximum stresses maximises the degree of mechanical coupling between the active piezoelectric layer and the resonator for generation of both driving forces and sensing signals. Very high quality factors of 3100 and higher have been experienced. Furthermore, the resonator can be manufactures by batch production techniques while maintaining high reliability and reproducibility.

Description

technical field [0001] The present invention relates to a resonant sensor assembly. Background technique [0002] Resonant sensors have been used in a wide variety of sensing applications, capable of measuring load, pressure, torque and fluid flow characteristics. A key component of any sensor is the resonator, an oscillating structure designed such that its resonant frequency is a function of the measurement. [0003] The most common sensing mechanism is a pressurized resonator used as a force sensor. The applied stress effectively increases the stiffness of the resonator structure, which results in an increase in the natural frequency of the resonator. The resonator provides a true digital frequency output, which is less affected by electrical noise and independent of the level and attenuation of the transmitted signal, providing good long-term stability. This frequency output is suitable for digital interfacing and requires no analog-to-digital conversion, thus maintai...

AI Technical Summary

Problems solved by technology

This technology is about 40 years old, and the performance of strain gauges is mainly limited by aging and creep deformation

[0006] The manufacture of resonators utilizing such techniques is relatively expensive and labor intensive and thus difficult to automate

Images