Stability and durability of resonant SAW strain sensors

Resonant SAW strain sensing elements used in non-contact torque, force and vibration sensors are investigated from the point of view of their stability and durability. Results of fatigue testing of the SAW sensing elements bonded to metal shafts with a stiff adhesive are presented. They demonstrate the sensor durability and stability of the strain sensitivity up to 13 million strain cycles. Stability of the frequency of the SAW differential resonant sensing elements is also investigated demonstrating an estimated sensor zero drift of 0.8-0.15 microstrain per year.