Educational instruction for definition of air movement by anemometers

Air movements in ventilating apertures define speed of movement of atmospheric air with anemometers: 1 type (at the speeds from 1 to 50 m/s) and 2 type (0.5-10 m/s) (fig. 1). Work vertically established anemometer of 1-type does not depend on the wind direction; anemometer of 2-type need to focus accurately at the axis wind direction.

Fig. 1. Anemometers

(a – second type; b- first type)

For definition of speed of air movement you have to write down initial indicators of dials of the counter (thousand, hundreds, tens and units), having disconnected it from anemometer at the research place (for example, in an alignment of ventilating aperture). In 1-2 minutes of single rotation include simultaneously the tachometre and stop watch. In 10 minutes the counter disconnect, read new instruments of dials and count speed of rotation (quantity of divisions of the scale of anemometer – see formula A):

А = ,

where: N₁ - indications of scale of the device before measurement;

N₂ - indications of scale of the device after measurement;

t - duration of measurement in seconds.

On value "A" divisions/seconds under the schedule (everyone anemometer has the individual schedule according to factory number of the device, which is applied to anemometer), find speed of movement of air in m/s.

Appendix 3

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