Airflow Instruments AV 30 Panduan Petunjuk Pengoperasian - Halaman 5

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The instrument will function satisfactorily in an angular position but

should not be used in airstreams which are smaller than the entire face

area of the measuring head (113mm diameter). The AV30 is calibrated

for use in free air conditions. For smaller airstreams TSI Instruments

Ltd. thermal type anemometers are recommended.

4.2

Checking air velocity or volume flow rate over larger areas.

When checking air velocity or volume flow rate over larger areas, a

number of 'spot' readings should be taken and recorded to give

coverage over the whole area.

When taking 'spot' readings, it should be noted that quite large

variations might be observed between individual readings. In general,

the more readings taken, the more accurate the result will be. It does

not matter if the positions of the readings overlap somewhat, so long as

they are equally spread to cover the entire area.

5. Use on Grilles

Note: See Comments under section 7 'Possible sources of error'. Avoid

intrusion of the hand, arm or handle of the instrument into the face area of

the grille. The blockage effect created by this would cause artificially high

velocity over the remainder of the grille, leading to additional errors.

Better measuring conditions can be obtained on grilles with adjustable

direction vanes if the vanes on the grilles are temporarily straightened

before making measurements. This should not significantly affect the flow

rate so long as any built in dampers are not accidentally disturbed. It is

advisable to use the aperture, not the surface area of the grille in any flow

calculations.

The instrument is suitable for both supply and extract grilles, and the

procedure for both is the same except that the measuring head must be

rotated through 180

Whilst it is acceptable to hold the anemometer head against the grille in

extract it is usually recommended to hold it slightly away from the grille

face on supply to avoid excessive turbulence and any vena-contracta

effects.

to align the direction arrow correctly.