+GF+ 2298 Bedienungsanleitung Seite 17

Instruction manual
Gases / Steam
In a closed (especially outdoors,
exposed to direct sunlight) tank,
vapors/gases above the liquid
may reduce the millimeter-
wave signal transmission.
4.1.2 Flow measurement applications
The instrument can be used for open channel flow measurement with the flumes and weirs.
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The distance of the sensor from the surface must be adjusted, taking into account the maximum level to be measured and the
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proximity linearization error curve.
The sensor must be positioned on the longitudinal axis of the restricting element at a location determined by the characteris-
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tics of the restricting element. This point is marked on Parshall flumes.
Foam may form on top of the flowing liquid which may affect the measurements. The liquid's surface must be exposed in front
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of the sensor to obtain a good echo.
The sensor must be fixed so that it cannot move.
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The correct construction of the upstream and downstream sections of the measurement channel is of utmost importance for
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the accuracy of the measurement.
The accuracy of volume flow measurement based on the level change also depends on the size and design of the restrictive
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element (channel or weir) used and the surface quality of the flowing liquid (ripple, foam). Therefore, flow measurement accu-
racy is necessarily lower than the accuracy achievable with level measurement.
The sensor must be protected from direct sunlight by a cover to prevent the sensor from exceeding the maximum permitted
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temperature.
Empty Tank
Especially in the case of tanks
with convex or conical bottoms
or tanks with equipment (e.g.,
heating element, mixing
paddle) at the bottom, the
device may indicate an
incorrect level when draining
completely. It is because the
tank bottom or objects at the
bottom of the tank scatter or
reflect the millimeter waves
emitted to a certain extent, or
the lower signal level of the
scattered radiation interferes
with itself in the tank. At least
100 mm (3.9") of liquid must
cover these interfering devices
or the convex or conical tank
bottoms for a reliable measu-
rement.
Temperature
The sensor must be protected
from direct sunlight to avoid
exceeding the highest permit-
ted temperature.
Type 2298 80 GHz Radar Level Sensor
Foam
Foam on the measured surface
may prevent millimeter-wave
level measurement. The sensor
should be mounted in a position
below where the formation of
foam is the smallest.
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