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6.4.5 Volume flow measurement

To determine the volume flow VF in ventilating channels multiply average flow

velocity ¯v by cross-section area CS.:

VF = ¯v

0.36 VF = m

/h, ¯v = m/s, CS = cm

For approximate air volume measurements at air vents and gratings the aver-

age flow velocity can be determined by means of time-based averaging. Or al-

ternatively the average flow velocity can also be determined by single network

measurements as per VDI/VDE 2640 with manual single measurements at de-

fined points (e.g. 13.24 m/s) (see 6.4.3 and Manual 3.5.5).

Continuous volume flow measurement can also as a special case be performed

by means of pure center point measurement. Averaging over several points

can thus be omitted. Volume flow calculation is then based automatically on

the measured value only. Measured value smoothing (see Section 6.4.1) is de-

finitely advisable. The K factor for correcting the flow profile, as factor for the

volume flow channel, should be set to 0.8; (see below).

Volume flow function channel

To show the volume flow data a function channel is required whose reference

channel is aligned to the flow measuring point and / or to the appropriate aver-

age value channel M(t); (see Manual, Section 6.3.4). The easiest way to do this

is to program the measuring range ´Flow´ on the 2nd or 3rd channel of the flow

sensor.

If this channel has not yet been activated, it must be selected in the

RANGE function by pressing and holding down the M key and

programming the measuring range ´Flow´ (see Section 7.7). The re-

ference channel is automatically set to the 1st channel, Flow.

Programming example for a rotating vane as flow sensor:

1st channel e.g. measuring point M01 Measuring range ´S220´ Averaging mode ´Cont´

2nd channel e.g. measuring point M11 Measuring range “Flow” Cross-section 175 cm

Or alternatively the function channel ´Flow´ can be programmed to internal

channels M3 etc.

The reference channel for this measuring point is M01; i.e. the flow sensor

must be connected to M01; (see Section 7.7). The advantage of this variant is

that any flow sensors can be used without the need for additional programming

steps.

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