Oscillator-based strain gauges employing surface acoustic wave resonators for wireless sensor network

An oscillator based strain sensor was developed. In this device, a surface acoustic wave (SAW) resonator was used as not only a frequency reference for the oscillator but also a sensor head with high sensitivity. Our sensor was applied to the tensile test based on the industrial standard (JIS Z2241). It was confirmed that the shift of the oscillation frequency was proportional to the strain, and the sensor can detect the strain of 10^-6 order. Extraction of this frequency shift was demonstrated using a commercial mixer chip with down-conversion technique. As a result, it was also confirmed that the converted frequency was proportional to the applied strain.