MOUNTING GUIDELINES FOR AIR VELOCITY MEASURING DEVICES
For accurate measurement results it is of paramount importance to place the sensing probe at a location with low turbulence, such as
after filters, rectifiers, heaters or coolers. Turbulence appears after obstructions like fans, bends, junctions or section changes in the
duct (diffusers / confusers), so the probe shall be placed far enough from these. The minimum length of the settling zone (straight duct
section without obstructions whatsoever) between the probe and the source of turbulence depends on the diameter of the duct. An
“equivalent diameter” D
gl
can be defined for a rectangular duct with dimensions a · b:
The following pictures supply guidelines for correct installation of air velocity transducers with respect to location and to minimum
recommended settling zones.
+
<6D
<6D
>3D
>3D
>6D
>6D
>6D
Install the sensor in the middle of the duct.
The preferred position of the sensor is after a filter.
Place the sensor in front of the diffusers at a position with high air
velocity.
Place the sensor at a position with laminar (non turbulent) flow.
Turbulence appears after fans as well as after bends, junctions, air hea-
ter, air cooler, filters, flaps or diameter changes in the duct.
MAINTENANCE OF THE E+E AIR VELOCITY SENSORS
Due to the absence of moving parts, the E+E air velocity sensors are not subject to wear. The construction (shape, dimensions and
materials) of the hot film air velocity sensor is per se highly insensitive to dust and dirt. No maintenance is required under normal
environmental conditions. For operation in polluted environment it is advisable to periodically clean the sensing head by washing it in
isopropyl alcohol, preferably in an ultrasound cleaner. Alternatively shake it gently few minutes in a pot with isopropyl alcohol and let it
dry free. Do not touch or rub the sensor and do not use any mechanical tools for cleaning.
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