This a high precision and high accuracy type of manometer. It is used to measure the minuscule amount of pressures with high accuracy.Its configuration is inclined and this makes it more accurate than other types of manometers.It is used where manometric properties of liquids are very close.
If the manometer, instead of being vertical, is set at an angle θ to the horizontal, then a pressure difference corresponding to a vertical difference of levels x gives a movement of the meniscus s = x/sinq along the slope.
If θ is small, a considerable magnification of the movement of the meniscus may be achieved.
Angles less than 50 are not usually satisfactory because it becomes difficult to determine the exact position of the meniscus.One limb is usually made very much greater in cross-section than the other. When a pressure difference is applied across the manometer, the movement of the liquid surface in the wider limb is practically negligible compared to that occurring in the narrower limb. If the level of the surface in the wider limb is assumed constant, the displacement of the meniscus in the narrower limb needs only to be measured, and therefore only this limb is required to be transparent.