Abstract: A level detector comprises an array of light emitting devices mounted in a line parallel to an array of light receiving devices, the arrays being mounted within a housing capable of internally reflecting light from the emitting devices to respective receiving devices unless the respective parts of the level sensor are immersed in liquid. The outer internally-reflecting surface of the housing is preferable a continuous straight-line surface along the direction parallel to the arrays.

Abstract: Medical infusion apparatus comprises a housing in which a standard flexible liquid reservoir is disposed. A constant-force spring applies pressure to the reservoir to force liquid out of the reservoir and along a conduit to a patient. The spring is energized by the opening of a lid of the housing which permits replacement of the reservoir.The liquid flowing out of the reservoir passes through a molded conduit part which is configured so that it is positioned at a predetermined location with respect to a flow monitor. The flow monitor injects a pulse of heat, and detects the rate at which the heat pulse travels along the conduit. A microprocessor uses the sensed flow rate to control a stepper motor which regulates fluid flow by squeezing the conduit via a spring-biased member. The apparatus has active and standby modes in which the monitor is operated respectively more and less frequently.