Quantitative dispenser for a liquid.

摘要

A quantitative dispenser for a liquid includes a pipette (3) having a downwardly directed nozzle (4) which serves to pick up and deliver a predetermined quantity of a liquid, and a mechanism for moving the pipette (3) downwards to dip the lower end of the pipette (3) into the liquid supply. A detector (10) is provided for detecting for reflection of light which is projected downwards to the surface of the liquid while the pipette is moved downwards to approach the surface. A control circuit is connected to the detector (10) to determine the stop point for the downwardly moving pipette with the aid of information received from the detector (10). The detector (10) has a spot type reflection sensor (32) having a light convergent optical element (34,36) with a focal point at a certain distance below the detector (10) whereby the stop point of the downwardly moving pipette (3) is determined so as to correspond to a point of maximum intensity of the incoming reflected light.