| 摘要 |
<p>A differential pressure transmitter (42) is used to measure the level of settled water (14) residing below a process fluid (12) and at the bottom of a tank (10). The pressure transmitter (42) measures a pressure difference between a pressure tap (48) of the tank located below an upper level of the higher specific gravity settled water and a second pressure tap (24) of a reference column (22, 86, 88) containing only lower specific gravity process fluid and opening to the tank (10) at a level (26) above the settled water. The differential pressure is a function of the specific gravity or density of the water (14) and a pressure head of the waterc (14). Utilizing the differential pressure and specific gravity data the height of the water (14) in the tank (10) can be determined. The reference column (22, 86, 88) is capable of being purged to remove any water or other impurities. A portion of the reference column (22, 86, 88) extends at least as high vertically as the lighter fluid (12) in the tank (10). The reference column can be a separate column (86, 88) that can be closed off from the tank (10) to permit the differential transmitter (42) to sense differential pressure changes due to level changes of fluid in the tank (10).</p> |
