Palladium-silver mesowires are prepared by electrochemical decoration of graphite step-edges with a good control of the alloy composition and wire diameter. As-prepared arrays are used for hydrogen sensing and demonstrate extended detection capabilities up to the whole concentration range of H(2) depending on the alloy composition. At low silver content, low hydrogen concentration is detected but the sensing window is narrow because of sensor saturation. The sensing window is advantageously extended to higher hydrogen concentrations for quantitative measurements up to pure H(2) flows with Ag-rich alloys. The mechanism responsible for these behaviors implies the statistical distribution in surface composition rather than the structural characteristics and stability domains of the corresponding hydride phases.