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Absolute measurement method (SG)
With the absolute measurement method, the prevailing total pressure on the level sen-
sor is determined (= air pressure + hydrostatic water pressure). To compensate for
the influence of fluctuations in air pressure, a second data logger is positioned on the
surface as a barometer.
Advantage:
very robust, impervious to ambient humidity
Disadvantage: no integrated air pressure compensation
Absolute/absolute measurement method (A/A)
Total pressure and air pressure are each determined by means of a pressure sensor
(A/A technology) and are calculated mathematically in the device by subtracting the two
measured values. A sensor cable without a capillary tube is used for this measurement
method, and this is why AA systems are highly resistant to the ambient humidity prevail
-
ing at the measuring point.
Advantage:
very robust, impervious to humidity or flooding
Disadvantage: slight reduction in measurement accuracy because of measurements
by two sensors
Level measurements in closed receptacles
For level measurement in closed receptacles/vessels,
the internal pressure in the vessel is measured instead of
the air pressure. The A/A measurement method is usually
selected on account of the humidity prevailing inside the
vessel.
Air pressure
Internal
pressure
Water
pressure
