Electromagnetic radiation from an optical source is directed onto an optical aperture in a metallic structure. By using a measure of the fueling rate, the air side control may, for example, anticipate the future air side needs of the engine, and adjust one or more air side parameters to meet the anticipated future air side needs of the engine. The tension of a seat belt does not affect the weight sensing functionality of the weight sensor and the state of the seat can accurately be determined. Preferably, the anchor is expandable to set in wellbores of various sizes and either cased or uncased.