| 摘要 |
The present invention relates to the measurement of the level of a liquid, and particularly to the measurement of the water level in a borehole. A liquid level measurement device (1) comprises a processor (42) for calculating a liquid level (13), a float (12) and an elongate sleeve (4), the float (12) being free to float inside the sleeve (4) and to move along the length of the sleeve under the influence of a changing liquid level (13') inside the sleeve (4). The sleeve (4) has a plurality of graduations (10, 11) spaced along the length of the sleeve. The float has at least one optical sensor (26, 27, 28; 26', 27', 28') in communication with the processor (42) for sensing the graduations (10, 11) as the float (12) moves along the sleeve (4). The processor (42) is arranged to calculate from the sensed graduations (10, 11) changes in the level (13') of the liquid (14) inside the sleeve (4).
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