U type Absolute Pressure gauge
This is a simple U-tube arrangement for the measurement of the absolute pressure.One leg of the tube is completely evacuated and the other open to the atmosphere.
Mercury is used as the manometer fluid. For pressures between 0.03 and about 10 mm Hg, oil manometers are more accurate than mercury manometers, since oil has a much lower density. For example, dibutyl phthalate, which is often used, has a density of 1046 kg/m3 at 20 DegC (PHg=13590 kg/m3). The absolute pressure is given by.
p(in mm Hg )= (poil/pHg )h
where h is the reading of the oil manometer in mm.
U-Tube Manometer
A liquid of know density (mercury, water, light oil,etc.) is placed in the connecting legs of a U-shaped in the glass tube. Each arm is connected to a separate region and the manometer is used to obtain differential pressures. The difference in pressure is given by
delta P = pgh
where h is the difference in the height of the liquid columns.
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