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11. Measuring with the measuring menus
11.4.9 Volume flow measurement
The volume flow in flow channels can be cal-
culated by multiplying the average flow velocity
and the cross-section surface.
needed for this purpose can be accessed via
the user menu U3
these are a flow channel with averaging, the
functions "diameter" and "cross-section", and a
function channel for volume flow (see 12.3.10).
If the volume flow channel has not yet been pro-
grammed or if other functions are needed, e.g.
profile factor or length and width for rectangular
cross-sections, you can use the wizard menu
.
Volume flow
Volume flow VF = average flow velocity
v
VF =
The average flow velocity
and gratings the average flow velocity can be determined by means of time-
based averaging (see 11.4.5 and Manual 3.5.5). You apply the rotating vane
at one end, start averaging, and proceed uniformly over the whole cross-sec-
tion; when you reach the other end of the cross-section stop averaging.
Or alternatively the average flow velocity can also be determined by means of
single array measuring operations as per VDI/VDE 2640 (see 11.4.4 and
Manual 3.5.5) (e.g. 13.24 m/s).
To display, output and save the number of measuring operations the
function channel ´n(t)´ is also provided (see 12.3.9, 12.3.10).
With Pitot tubes, in order to calculate actual velocity, temperature compensation
and atmospheric pressure compensation must be provided.
The average velocity is shown by the function
Enter the diameter in mm (maximum 2000):
Enter the cross-section surface CS directly in cm
Display the volume flow VF in a
function channel in m
To output all function values of the menu press
Converting to standard conditions
With all flow sensors it is possible to convert the actual measured values to
standard conditions, i.e. temperature = 20°C and atmospheric pressure = 1013
mbar. To do this ´#N´ must be programmed in the designation either in the
speed channel or in the volume flow channel only; this then automatically pro-
duces the standard volume flow.
46
ALMEMO
v
The functions
Volume flow
. CS . 0.36
v
For rough air volume measurements at air vents
3
/h:
®
5690-2M
C © REC COM l© ©l R01 * ´´´´´´µµµµ¶
±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±
01: 11.67 mls Volocity
|¹¹¹¹¹¹¹¹¹¸¹¹¹¹¹¹¹¹¹¸¹¹¹¹¹¹¹¹¹¸¹¹¹¹¹¹¹¹¹¸¹¹¹¹¹¹¹¹¹|¹¹¹¹¹¹®®®¸®®®®®®®®®¸®®®®®®®®®¸®®®®®®®®®|
5.00
Damping:
(see right);
Averaging mode:
Average value:
Counts:
Volume flow:
11: 8343. m
Diameter:
Cross section:
START MANU M PRINT ESC
v
• Cross-section surface CS
v
3
VF = m
/h,
v
Averagevalue: 3.24m¡
Diameter : 0150 mm
2
Cross-section: 175c¥
:
volume flow
11:
<PRINT>
S220 mls
CONT
13.24 mls
150 mm
175 c¥
2
= m/s, CS = cm
834.¦¢
15.00
20
12
/h
3
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