Each PZT was swept with 0-150V 11Hz triangular wave.
Time series data for 0.2sec was recorded for each PZT.
The swept voltage at the resonances were extracted and the fringe number was counted.
Some hysteresis is seen as usual.
The upward/downward slopes are fitted by a linear line.
The average displacement is 11.3nm/V for PZT1 and 12.7nm/V.
The PZT response was measured with a FFT analyzer. The DC calibration was adjusted by the above numbers.