MEMS whistle-type temperature-compensated displacement sensor using resonant frequency shift

Sound from a whistle can be modulated by adjusting the length of the whistle's resonant tube. Using this principle, a whistle-type displacement sensor has been previously proposed but has not been achieved because of technological constraints. Owing to the precise flow control techniques presently available as well as the high processing accuracy, advanced miniaturization, and high-density integration capabilities offered by MEMS technology, we have developed microelectromechanical systems (MEMS) whistle-type displacement sensors that use only acoustic signals to measure displacement. The MEMS whistle-type displacement sensor was 5.0 mm in length, 2.1 mm in width, and 1.4 mm in thickness. The sensor achieves precise displacement measurement with a possible error of a few μm. Furthermore, the range of the deviation caused by a temperature change of 10 °C was reduced by approximately 90% when an additional whistle-type sensor was used as a temperature compensator, for an input displacement of 200 μm.