Abstract: A bubble detection system for use in a fluid delivery line leading to a patient for automatic delivery of a fluid. The system monitors a parameter indicative of compressibility of the fluid being delivered and compares that monitored parameter with a known value of the same parameter using a relatively incompressible fluid. If the fluid being delivered is more compressible by a predetermined amount, the system recognizes the existence of a bubble and stops the further movement of fluid toward the patient and reduces the pressure in the fluid delivery line upstream of the bubble to prevent the bubble from progressing further toward the patient. The parameter may include pressure in the fluid delivery line, force required to deliver the fluid or motor current in the event an electric motor is used in delivering the fluid.

Abstract: A rotation-sensing device for providing output signals that correspond to rotary hand movement made about the device by an operator is disclosed. The device comprises a cover member including an outer surface having a generally cylindrical, longitudinally elongate, non-rotatable protusion carried thereon. The protrusion projects outwardly from the outer surface and is provided with an outer periphery thereon. The device further includes a plurality of generally longitudinally elongate, circumferentially spaced, sensing means which are positioned adjacent the outer periphery of the protrusion and are responsive to the rotary hand movement of the operator for providing output signals corresponding to such movement. In addition, the device includes means coupled to the sensing means for leading the signals generated in the sensing means away from the switch device.