Sensitivity enhancement of piezoelectric force sensors by using multiple piezoelectric effects

The sensitivity enhancement of piezoelectric force sensors is investigated based on multiple piezoelectric effects in this paper. At first, theoretical analysis showed that multiple piezoelectric effects had an influence on the piezoelectric force sensors. Secondly, a practicable method was adopted to perform the experimental validation and quantify the influence of multiple piezoelectric effects. In the method, different capacitors whose capacitances became much larger than that of the piezoelectric quartz sensor were in parallel with the quartz sensor. With the method, the details of the sensitivity enhancement of piezoelectric sensors were obtained. Experimental results showed that the sensor sensitivity increased from 4.00 pC/N to 4.07 pC/N when the capacitance of parallel capacitors was increased from 500 to 1000 and then 5000 times of that of the sensor. The force sensor sensitivity was improved by 1.75%. However, the nonlinearity and repeatability error of the force sensor were markedly increased with increasing the capacitance of the parallel capacitor. The method demonstrated that the piezoelectric force sensor sensitivity could be enhanced to a certain extent in the practical engineering, but it also brought some negative effects. Finally, further analysis indicated that multiple piezoelectric effects influenced the sensitivity by changing the piezoelectric coefficient. The well-known piezoelectric coefficient d11 of the quartz could actually reach 2.35 pC/N.