The design, construction, and operation of a high‐resolution electron‐energy‐loss spectrometer featuring a position‐sensitive resistive anode detector and differential pumping are described. The position‐sensitive detector provides a 66‐fold increase in acquisition speed over a single‐channel spectrometer. The differential pumping provides pressure isolation of 105between the spectrometer elements, except the lenses, and the sample region. An optically isolated multicomputer‐based control and data acquisition system provides complete spectrometer control and automated sample cleaning and characterization. The spectrometer, together with a differentially pumped supersonic molecular beamline, permitsinsitumeasurements of the interaction of a wide range of gas molecules with solid surfaces.