| 摘要 |
Liquid level is measured within a vessel of predetermined height by directing sonic or ultrasonic energy toward the liquid surface from both above and beneath the liquid surface, receiving energy returned from the liquid surface, and developing first and second signals respectively indicative of headspace above the liquid surface and liquid height within the vessel. These first and second signals are compared to the predetermined vessel height so as to identify apparently erroneous first or second signals indicative of a total liquid height and headspace either greater than or less than the predetermined height of the vessel. Level of liquid in the vessel is then determined as a function of the first and second signals not so identified as apparently erroneous. In this way, false signals caused by turbulence at the liquid surface or an inclined liquid surface are automatically discarded, yielding a more accurate reading of liquid level.
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