Abstract: A pump system and method for controlling and monitoring the aspiration of a liquid and the subsequent dispense of the liquid. As a pump is operated to either aspirate or dispense a liquid, a processor circuit receives input from a liquid air detector to sample the detected conditions in relation to the operation of the pump. In one embodiment, the pump employs a stepper motor, and the processor records information regarding the detected contents of the pathway at intervals correlating to the motor activity. A profile of detector output versus motor intervals is thus created from the point an aspiration cycle is commenced at least until a fluid-to-air boundary is detected, or from the point a dispense cycle is commenced, through an air-to-fluid boundary. Each profile is then compared against a standardized profile to determine if the detected transition occurred at a desired point in the profile.

Abstract: A failsafe apparatus for verifying a volume of aspirated reagent before it is provided to dilute a sample in an automated assay instrument. A pump draws reagent through a tube having a reagent probe disposed at one end. An optical flow detector includes an optical source disposed proximate the tube to illuminate the interior of the tube, and a photodetector oriented ninety degrees about the circumference of the tube from the source to detect reflected illumination from the contents of the tube. The photodetector provides one voltage level with gas/air within the tube, and a second level with a liquid within the tube. A circuit in communication with the detector discriminates between the two levels. The rate at which aspirate is pumped and the volume of the tube from a probe tip inlet to the detector are known constants. Therefore, a given volume of aspirate takes a predictable amount of time to pass from tip to detector.