Abstract: The present invention is directed to a valve that has an orifice closing member adjacent to an orifice through which fluid can flow, a displacement member having a first portion and a second portion, where the first portion is adjacent to the orifice closing member when the valve is in an open position, a first magnet and a second magnet where the first and second magnets are sufficiently proximate to the displacement member to exert a magnetic force on the displacement member, and an actuator for generating a magnetic field to move the displacement member toward the first magnet, cause the first portion to press against the orifice closing member, and cause the orifice closing member to close the orifice.

Abstract: A photo-acoustic flow meter for use in dialysis is described, that uses an optical beam to generate an acoustic signal in the fluid for which the flow rate is to be measured. The phase angle of the acoustic signal changes when traversing upstream and when traversing downstream. The phase difference between the acoustic signals received upstream and downstream, compared with a reference source signal is measured, and it yields the flow rate of the fluid.