| 摘要 |
An optical sensor (40) that provides a monotonic level-dependent output signal that varies smoothly and at an easily detectable rate over the entire length of the sensor includes first and second spaced waveguides (45, 50) extending along an axis, with each extending between its respective first and second ends. The first waveguide does not have surfaces contacting the liquid along the first waveguide's length. The second waveguide has at least a longitudinally extending portion of an outer surface in optical contact with the liquid. One or more web portions (50a, 50b, 50c) extend along and between both waveguides so that some of the light traveling along the first waveguide is coupled through the web portion(s) into the second waveguide. Light is injected into an end of the first waveguide (52), allowed to travel along the first waveguide, with a portion leaking into the second waveguide. Light is detected (55), with the amount representing the level of liquid.
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