Ahlborn ALMEMO 2390-5 Manual de servicio descargar pdf (Pagina 2)

Selecting the Right Flow Sensor

Sensor: Advantages Disadvantages

Thermoanemometer very small air flows can also

be measured (e.g. draft

measurements), non-direc-

tional measurement is pos-

sible

sensitive sensor electronics,

sensitive with regard to mech-

anical stress and contamina-

tion, sensitive with regard to

turbulent flow, high current

consumption, limited ambient

temperature

Rotating vanes high accuracy at medium flow

velocities and medium ambi-

ent temperatures, insensitive

to turbulent flow

sensitive sensor electronics,

sensitive to mechanical

stress, depending on direction

Pitot tubes copes with high flow velocities

and rough operating condi-

tions, high operating temper-

atures possible, easy to clean

highly depending on direction,

low flow velocities cannot be

measured, depending on tem-

perature,limited accuracy,

sensitive to turbulent flow

Positioning The Air Velocity Probe

The correct position of the sensing probe is the main condition for reliable and

accurate measurement of the air velocity.

Turbulence appears after fans as well as after turns, junctions or section

changes in the duct. Reliable measurements are only possible if the probe is

placed far enough from such places. The minimum distance is a function of

the duct’s diameter.

The equivalent diameter of a rectangular duct a x b is:

2 a b

a + b

3-5-2 ALMEMO

Sensors

1 2 3 4 5 6 7 ... 23 24

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Ahlborn ALMEMO 2390-5 Manual de servicio Pagina 2