Position sensing using an optical potentiometer

A simple optical potentiometer design is proposed for position sensing in large-scale structures during dynamic excitation. It consists of a long thin section of photoluminescent (PL) material with a length appropriate to the maximum expected movement and terminated by two photodiode detectors. The PL material and photodiode assembly are attached to the moving structure, and the material is excited by a light source that is fixed with reference to the moving part of the structure. Some of the emitted light propagates towards the ends of the material, where is it detected by the photodiodes. The intensity of the light in the PL material decays exponentially with increasing distance from the source. The relative movement between the light source and material and therefore the two parts of the moving structure are then deduced from the intensity of the light detected by the photodiodes. Since the potentiometer can be constructed of hermetically sealed components, it is suitable for outside environments.<
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