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Equal Column Liquid Manometer

This is one of the oldest methods of measuring differential pressure. In its most basic configuration it consists of two identical vertical tubes partly filled with a liquid. These tubes are connected together at the bottom. Pressure is measured by determining the change in height between the two tubes and is scaled according to the density of the liquid. Thus different fluids will give a change in the pressure range.

Typical fluids used are water and mercury.

The method is very accurate however is limited to lower ranges of pressure. It is rarely used today, however it used to be used quite extensively as a calibration standard for low pressure instruments and control valves. This role has now been taken over by highly accurate calibration tools. The following diagram depicts an equal column liquid manometer. It shows a glass tube bent into a "U" shape. This tube is partly filled with the fluid and a pressure scale is located between both tubes.

The Principle of an equal column "U" tube manometer
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