6
POSITIONING OF AIR VELOCITY SENSOR IN A VENTILATION DUCT
The reliable and accurate measurement of air velocity depends on the correct positioning of the sensor in the ventilation duct.
Accurate measurements are only possible if the air velocity probe is positioned at a location with a laminar (not-turbulent) flow.
The required length of the calming section after a fault is a function of the tube diameter D. For a rectangular channel a x b applies:
INCORRECT
CORRECT
+
<6D
<6D
>3D
>3D
>6D
>6D
>6D
Mounting the sensing probe in the middle of the
channel.
The optimal position is after the filter.
Please note sufficient distance.
Positioning the probe ahead of diffusor, at a place
with high flow rate.
Positioning the probe at a location with a laminar (to-
turbulent) flow.
Turbulent flows are caused by pipe bends, branches,
behind flaps, flans, air heaters, air coolers or cross-
sectional changes.
MAINTENANCE OF THE E+E AIR VELOCITY TRANSMITTERS
Due to the absence of moving parts, the E+E air velocity transmitters 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.
