| 摘要 |
A differential fluid level detector is disclosed for sensing the presence of a fluid medium at first and second preselected levels. The detector includes a light emitter, a longitudinally extending light transmitting body of a predetermined length in excess of the difference between the first and second preselected levels in optical communication with the light emitter for transmitting emitted light along a longitudinal light emission path, a light refracting means in communication with the light emitting means through the light transmitting body and at least one light sensor. The light refracting means includes first and second light refracting body portions which are respectively disposed at longitudinally spaced positions along the light transmitting body corresponding to the first and second preselected levels and each including a light refracting body portion bounded at least in part by a surface portion at an oblique angle with respect to the longitudinal light emission path. The respective surface portions define first and second external reflective interfaces adapted to communicate with the fluid to effect transmission of the emitted light into the fluid when each respective interface is in communication with the fluid and to effect internal reflection of the light when each respective interface is not in communication with the fluid along a predetermined light reflection path through the light transmitting body. The light sensor is disposed in optical communication with the predetermined light reflection path.
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