Next, a load resistor was attached to the device and the RMS
power was found. To find the optimal frequency of operation,
the power versus resistance was measured for several frequencies
around the resonant frequency. The frequency which achieved the
peak power was selected. The plot of power versus resistance for
0.1 g acceleration at the optimal frequency for each device at each
angle is shown in Fig. 7. Similar measurements were performed for
0.075 g and the optimal results are listed in Table 2. The table shows
the maximum output power for each device under each operating
condition. Additionally, the power output for the devices was measured
for accelerations from 0.05 g to 0.2 g, with the results plotted
in Fig. 8.