WEEGSCHAAL.

摘要

An optical detection system for a spring scale includes an apparatus for generating a moire interference fringe pattern and detecting the pattern movement to measure scale tare deflection and thereby determine the load weight. One of a pair of ruled parallel grating sets is fixed while the other is mounted to the tare structure in alignment with the fixed set. A lamp projects the interference pattern upon a photodetector array. The placement of a load upon the scale deflects the tare structure which results in a linear movement of the projected fringe pattern across the photodetector array and the resultant sequential generation of weight indicative signals. To compensate for variations in the spring constant of selected scale springs, the linear tare deflection required to provide movement of a given number of interference fringes past a reference is adjustable. This adjustment of effective spring constant is achieved by varying the angle of the gratings of the movable grating set.