Well-Type Manometer (Cistern Manometer)

About the well-type manometer or cistern manometer

The well-type manometer is effectively a U-tube manometer in which one-half of the tube is made very large and takes the form of a well. The change in the level of the well as the measured pressure varies is negligible. Therefore, the liquid level in only one tube has to be measured, which makes the instrument much easier to use than the U-tube manometer. The gauge pressure is given by:

P₁ = hp

It might appear that the instrument would give a better measurement accuracy than the U-tube manometer because the need to subtract two liquid-level measurements in order to arrive at the pressure value is avoided. However, this benefit is swamped by errors which arise due to the typical variations in cross-sectional area in the glass used to make the tube. Such variations do not affect the accuracy of the U-tube manometer.

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