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Load cell with surface acoustic wave resonator - has Y-cut quartz crystal substrate stressed by loading forces and bearing sets of aluminium reflective grids
Load cell with surface acoustic wave resonator - has Y-cut quartz crystal substrate stressed by loading forces and bearing sets of aluminium reflective grids
The load cell using surface-acoustic-wave principles consists of a Y-cut quartz crystal substrate (10) at the ends of which are sets of aluminium reflective grids formed by plasma beam etching and metallisation (12). Between the sets of grids is a transformer (14) formed from interlocking comb patterns by thin-film techniques. The whole forms a surface-acoustic-wave resonator. An oscillator (16) is connected to the resonator. The substrate is supported on a rigid element forming the loading beam of a load cell. When the beam is flexed, the oscillator frequency falls or rises, depending on the direction of force applied to the unsupported end of the beam, in the order of 55 Hz/gm in a linear fashion. With resonators on either surface of a quartz plate, a differential pressure/force transducer may be constructed.
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