On the Evaluation of the Sensitivity Coefficient of Strain Sensors

Sensitivity is one of the most important parameters for strain sensors. Appropriate evaluation of the sensitivity is of great significance in developing new strain sensors since, otherwise, misleading conclusions may be made. The estimation of the sensitivity coefficient of piezoresistive strain sensors based on the previously used expressions is highly dependent on the initial resistance R-0 and the sensor type (namely positive or negative). Here, it is clearly displayed that this will result in large inaccuracies in the sensitivity coefficient evaluation. Based on the modified expression by replacing R-0 with the instantaneous resistance R, the data for the sensitivity coefficient reported in literature are re-estimated. The results reveal that most of the so-called records reported in literature of the sensitivity coefficient are overestimated. The highest gauge factor reported so far is corrected from 1 000 000 to only 3313. On the other hand, the sensitivity coefficient for negative piezoresistive sensors is shown to be somewhat underestimated.