Figure 3.

Schematic of the setup for low-frequency calibration of the piezoelectric force transducer. The shaft of the piezoelectric force transducer is attached to the actuator through a tissue clamp. The shaft of a rigidly fixed, calibrated strain gauge (Sensotec Model 31) is attached to the body of the piezoelectric force transducer. Under sinusoidal oscillation at 1.0 Hz, the gain of the piezoelectric force transducer is adjusted to achieve identical dynamic output voltages from both the piezoelectric transducer and the strain gauge.