Cantilevered microbeam temperature sensor

摘要

Measuring devices employing resonant strain gauges, e.g. pressure transducers or accelerometers, are compensated for variation in temperature by employing a secondary resonant microbeam in combination with the primary microbeam of the strain gauge. The secondary microbeam is mounted in cantilever fashion, with one end of the elongate polysilicon beam fixed to a silicon substrate, while the remainder of the beam is free to oscillate relative to the substrate. An oscillating drive voltage is supplied to a drive electrode mounted on the beam and a substantially uniform electrical field is maintained in the region about the beam. The frequency of oscillation is controlled by a piezo resistor formed on the beam and used for detecting instantaneous beam position relative to the substrate. The cantilevered microbeam is free from the effects of residual or induced strain. Therefore, its natural resonant frequency depends upon temperature, as beam modulus of elasticity and density change with temperature. By contrast, the resonant beam of the strain gauge responds to induced strain and temperature effects. Outputs based on the natural resonant frequencies of the cantilever beam and the strain gauge beam can be combined to provide a strain gauge output compensated for temperature effects.