DEVELOPMENT OF A NONCONTACT LIQUID-LEVEL MEASURING SYSTEM USING IMAGE-PROCESSING

This paper describes how the authors developed a liquid level measurin g system designed to directly analyze images of liquid surfaces. This measuring system is based on the principle that the contour of the ima ge of a slanted metal strip placed in a liquid shows an inflection poi nt on the liquid interface. This liquid level measuring system using i mage processing is useful in automatically measuring the levels of wat er, oil, liquefied gases, and alcoholic beverages. Among the features of this measuring system are: (1) it is of the noncontact type, so tha t there is no need to install a sensor or other high-precision devices close to the liquid to be measured; (2) it can be installed in a way not affected by the liquid; (3) the scale and the liquid surface can b e analyzed on an image basis directly, so that periodic recalibration is unnecessary; (4) deviations in measurements can be easily detected by visually checking the monitor screen; (5) images from more than one camera can be processed with a single image processor to reduce total costs. (C) 1998 Published by Elsevier Science Ltd. All rights reserve d.