Meniscus position detector with detector at the focal plane of the lens formed by tube and liquid

摘要

A non-invasive photoelectronic device which determines the location of a liquid column within a transparent tube. The device includes a source of visible light, transmitted as a substantially parallel light beam against a transparent lensing tube which may be a sightglass or a leg of a U-tube manometer located within the light beam. The liquid contained within the tube forms an identifiable liquid column which acts as a highly effective condensing lens to the transmitted light beams with a resultant focus close to the tube. A plurality of optoelectronic detectors are arranged in an array over the portion of the tube to be monitored. Each detector is a phototransistor which is responsive to the large change in light intensity caused by the lensing effect of the liquid-filled tube compared to the non-lensing action of the adjacent portion of the tube.