A fluid proximity sensor for surface measurements having a measurement chamber (210) with a measurement nozzle (205), a reference chamber (220) with a reference nozzle (225), and a diaphragm (215) forming an interface between the reference chamber and the measurement chamber. A shroud (280) that encloses the measurement nozzle and reference nozzle provides a peripheral gap (295) between the shroud and a work surface (290) being measured. By connecting either a partial vacuum supply or a partial fluid supply to the shroud, the internal shroud pressure can be raised or lowered and thus the gain-frequency operating regime of the proximity sensor optimized. Movement of the diaphragm in response to differential pressure changes can be sensed by optical, capacitive or inductive means (275).