Piezoelectric sensors have been previously used for continuous structural health monitoring using impedance spectroscopy. However, three important issues still remain to be investigated for efficient design of such sensors, namely (i) the effect of sensor geometry on sensitivity of impedance based damage detection, (ii) the selection of frequency band for continuous health monitoring, and (iii) identification of damage quantification metric. In this study, we address these issues and report the results on aluminum beam subjected to mechanical fatigue. A commercially available Materials Testing Machine was used in order to perform a load controlled fatigue test (250-1350 lbs @ 20 cycles/sec) on a notched aluminum beam. Sensor geometry was optimized with the help of damage index metric based health monitoring. Next, optimized geometry was selected to further study the selection of frequency band with a new approach based on number of peaks in the impedance signature under identical testing conditions. The results of this study provide a benchmark for designing the sensors for structural health monitoring. © 2011 Copyright Taylor and Francis Group, LLC.