Ahlborn ALMEMO 2390-5 Manual de servicio descargar pdf (Pagina 19)

Rotating Vanes

3.5.4 Rotating Vanes

For flow measurements the ALMEMO

sensor range provides the rotating

vanes FV A915-Sxxx with an exchangeable snap-on head or the type FV

A915-MA1 with a fixed measuring head. They are especially suitable for use in

air conditioning. The air velocity can be activated and displayed with the correct

scaling and dimension by every ALMEMO

measuring instrument.

Measuring Principle

The flow velocity is determined by means of a

frequency measurement. The flowing medium

initiates the movement of the rotating vane. By

an inductive pulse count, which is performed us-

ing a microcontroller and is integrated in the AL-

MEMO

connector, the revolutions of the rotat-

ing vane are measured and displayed as

velocity.

Measurement

To obtain correct measuring data with a rotating vane measuring probe the

shaft of the rotating vane must be aligned in parallel to the flow direction. If the

measuring probe is slightly moved in the air flow, the value indicated at the in-

strument will change. The measuring probe is correctly placed in the air flow,

when the indicated value is at maximum. When flow measurements are per-

formed using rotating vanes there can be measuring situations with a very in-

homogeneous flow profile:

- Measurement at air outlets:To obtain correct measuring data the measure-

ment must be performed some distance away from the grill-screen and

large rotating vanes must be used allowing the measured values to be in-

tegrated and averaged over the larger measuring head. If smaller rotating

vanes are used it is necessary to average either spatially over individual val-

ues or over a specific time.

- Measurements at air intakes:To obtain defined flow conditions in a fixed

cross section the rotating vane is positioned in a measuring hopper.

ALMEMO

Manual 3-5-19

1 2 ... 14 15 16 17 18 19 20 21 22 23 24

Sin comentarios

Ahlborn ALMEMO 2390-5 Manual de servicio Pagina 19