Abstract: A hydrophone has a pair of end caps each disposed on a different open end of an air-backed cylinder of a piezoelectric ceramic material. An electrode or lead extends through one of the end caps and into the cylinder, and has a shape and a lateral width that extends across an interior of the cylinder and abuts an inner surface of the cylinder at multiple points.

Abstract: An apparatus for sensing and correcting force levels and vibrational frequencies in a cylindrical grinding machine which has active centers. The active centers have imbedded shear load sensors and imbedded actuators. The sensors provide real time grinding information and allow for a determination of undesirable force levels and vibrational frequencies. The actuators are a pair of piezoelectric stacks disposed on opposing sides of the center body in indentations. A voltage applied by a controller causes the piezoelectric stacks to expand and contract. The action of the piezoelectric stacks causes the tip of the center to laterally displace and apply a lateral force to the workpiece. An AC voltage waveform may be applied for force control. A DC voltage may be applied for displacement; for example, to rapidly remove the workpiece from the grinding wheel or to correct for misalignment between the workpiece and the wheel.