US Patent 7215252 Proximity sensor

A proximity sensor includes an antenna having a resonant frequency selected to correspond to a resonant frequency associated with a selected dimension of an item of interest. In one example, the antenna is selected to have a resonant frequency corresponding to a resonant frequency associated with the width of a turbine blade. The amount of electromagnetic coupling between the item of interest and the antenna provides an indication of the proximity or distance between them. Several embodiments for incorporating such a structure into a gas turbine air seal are disclosed.