manometer
The manometer indicates gas pressure by the rise of liquid in the tube.
Instrument for measuring the pressure of liquids (including human blood pressure) or gases. In its basic form, it is a U-tube partly filled with coloured liquid. Greater pressure on the liquid surface in one arm will force the level of the liquid in the other arm to rise. A difference between the pressures in the two arms is therefore registered as a difference in the heights of the liquid in the arms.
| If the greater pressure is P1 pascals and the lesser pressure is P2 pascals, then: |
| where h is the difference (in metres) in the heights of the liquid, d is the density (in kilograms per cubic metre) of that liquid, and g is the gravitational field strength (in newtons per kilogram). If P2 is atmospheric pressure, then hdg gives the pressure difference between P1 and the atmosphere. |
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