An embodiment includes determining a temperature change of a fluid-ejecting substrate, and determining a mass of fluid ejected from the fluid-ejecting substrate from the temperature change of the fluid-ejecting substrate. The vehicle is simple and compact. A pair of spaced wheel assemblies is provided including a bracket having a lower portion connected to the upper door frame and an upper portion carrying a pair of rollers received by the roller mounting portion. The detection logic is expandable to detect future protocols.