| 摘要 |
A liquid level system comprising: a frame having a measuring surface; an observation tube having a first end, a central portion and a second end and a longitudinal axis, the observation tube being filled with a liquid sufficient to create a positioning bubble within the observation tube and the observation tube mounted to the frame such that the longitudinal axis of the observation tube is at a predetermined angle relative to the measuring surface; a first light source mounted to said frame in a position such that the light emitted from the first light source is directed at the observation tube; an electric power source affixed to said frame and electrically connected to form a circuit with the first light source for energizing the first light source.
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