A resonant tuning fork force sensor with unprecedented combination of resolution and range

This paper presents a double-ended tuning fork (DETF) force sensor with a resolution of 7nN and a range of 0.12N. The resonator has a scale factor of 216 kHz/N, a Q-factor exceeding 60,000 at 3mTorr ambient pressure and a zero-load resonant frequency of 47.6 kHz. The sensor and the complete readout circuit are fully embedded in a compact 65 mm × 52 mm printed circuit board (PCB). The PCB is mounted on a micro-stage and coupled with an off-the-shelf displacement actuator to realize an economical, versatile and robust micro mechanical test frame with unprecedented combination of force and displacement resolutions and ranges.