Water Level measurement using static Pressure
The pressure at any point below the surface
of a liquid and the level of water in height are related directly. Simply, the
pressure at any point below the liquid surface is a measure of liquid level.
Level measuring instruments using static pressure utilize this principle.
Static pressure type level instruments are
normally only applied to open vessels, because they depend entirely on the
static head. Any change in pressure on the surface of the liquid would affect
the calibration, because it would cause a change of static head pressure. The
pressure and Level relation can be summarized using the equation
h=P/ρg
where, h=height
or level
P=pressure due to hydrostatic head
ρ=density of the liquid
g=acceleration due to gravity
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| level measurement using static pressure |
The instruments like a simple U-tube manometer, Bourdon tube, diaphragm type, air bubbler or any low pressure instruments are used to measure static pressure in this type of level measuring instruments.
A typical example for a system where this type of instrument used is the condensate storage tank in power plants. Because of its remote location, and the need of the operator to monitor its level, some type of indirect measurement is required. A differential pressure type is not suitable for this system because of the inability to maintain a constant reference leg. Therefore, the static pressure-system is best suited.
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