Bar coding scheme for sensing media type and quantity on a rotating supply tube

摘要

In a pen plotter having plotting media supplied in the form of plotting media supply rolled around a hollow tube, this is a method and apparatus for automatically identifying the type of, and measuring the amount of, plotting media contained on the plotting media supply roll. A circular barcode strip is secured to the inner surface of the supply tube and is optically scanned to reveal the identity of the media contained on the supply roll. Said barcode strip's properties allow for the determination of the rotational velocity of the supply roll which, when used in conjunction with other known and easily derivable pieces of information, also allow for the precise calculation of the amount of media remaining on the roll. Knowing the identity of the media on the roll allows the plotter to handle the media in a manner consistent with its properties. Knowing the quantity of media remaining allows both media low and media out conditions to be determined and alarmed.