| 摘要 |
A hypsometric liquid such as water is supported in a closed chamber on a tubular column of mercury, the mercury being exposed in a manometric manner to atmospheric pressure so that variations in the atmospheric pressure increase or reduce the height of the mercury column. Also, an increase in pressure applied to the hypsometric liquid reduces the height of the mercury column since the liquid rests directly on the mercury. The hypsometric liquid is heated in a controlled manner to produce a vapor that exerts pressure on the liquid and the mercury column. As the temperature is increased by the heater, the mercury moves down the tube until it reaches a constant or fixed level at which sensor electronics adjust the power to the heater so that the top of the mercury column remains exactly at this fixed level. The pressure on the liquid is determined by measuring the temperature inside the hypsometric chamber. Atmospheric pressure is essentially equal to the hypsometric chamber pressure plus the pressure equivalent of the mercury column.
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