Given the success of online shopping platforms and e-commerce technology, there is an increasing necessity to quickly and safely package different types of items. Addressing this necessity requires technology to accurately measure items at a high speed. Existing studies, however, lack in terms of reproducibility and the diversity of the items measured. In this paper, we present a novel approach for item measurement, targeting automated packaging systems that make use of belt conveyors. In particular, leveraging a scenario-driven approach and an automata-based control design, we describe in detail the creation of a real-world prototype for belt conveyor-based item measurement. Experimental results obtained for this prototype demonstrate that it is possible to measure different types of items (boxes, books, household items) with a mean error of less than 3.02mm and a standard deviation of less than 2.34mm, for a maximum conveyor belt speed that is less than 0.5m/s and a maximum calculation time of 20ms.