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Manometer
Intermediate
Measures gauge pressure with a U-tube.
A U-tube partially filled with liquid measures pressure differences: ΔP = ρgh. One side connects to the gas, the other to the atmosphere or another gas.
A 20 cm water difference means 1.96 kPa gauge pressure.
Gauge pressure relative to the atmosphere.
In more detail
A manometer measures the pressure difference between two points using a liquid column in a U-tube. The height difference of the liquid gives the pressure difference.
Real-world uses
- Blood pressure cuffs and gas pipelines use manometers.
- Laboratory experiments measure gas pressure in sealed vessels.
- Engineers measure the pressure in a gas line with a U-tube manometer, reading the difference in liquid levels.
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Frequently asked questions
What liquid is used?
Water, mercury or oil, depending on the pressure range.
How is pressure found?
Multiply the height difference by the density of the liquid and g.
What does a manometer measure?
The difference between the pressure being measured and the reference pressure, usually the atmosphere.
Related topics in Fluids & Elasticity
Hydraulic press · Atmospheric pressure · Barometer · Gauge and absolute pressure · Buoyancy · Archimedes' principle