One of the main calibration services of African NMIs (National Metrology Institutes) isthe measurement of tapes and rules. This is mainly regulated by legal metrology and OIML(International Organisation of Legal Metrology) specifications are therefore referenced.Specifically, OIML R-35 is the standard to which rules or line scales must conform. Theaccuracy of most African NMIs systems however, cannot prove conformance to thisspecification. This article will detail the development of a new, cost effective, linescale calibration system, which will have accuracy better than the specificationprescribed. The system was locally developed and its design is based onoff-the-shelf components and open source software. It is alsoready-for-upgrade to an absolute system. The system and details of theline detection algorithm will be presented.
