10. Measuring using Measuring-Menus
43
10.4.9
Volume Flow Measurement
The
volume flow
in flow channels can be calcu-
lated by multiplying the average flow velocity
and the cross-section surface. The functions
needed for this purpose can be accessed via the
´User menu´ U3
Volume flow
(see on the right);
these are a flow channel with averaging, the
functions ´diameter´ and ´cross-section´, and a
function channel for volume flow (s. 11.3.10) If
the volume flow channel has not yet been pro-
grammed or if other functions are needed, e.g.
factor or length and width for rectangular cross-
sections, please refer to the help menu
Volume
flow
.
Volume flow
VF = average flow velocity
• cross section area CS:
VF =
. CS
. 0.36
VF = m
3
/h,
= m/s, CS = cm
2
For rough air volume measurements at air vents the
average flow velocity
can be determined by a
time-based averaging
(s. 10.4.5 a. man. 3.5.5).The
rotating vane must be applied at one end, the averaging has to be started and
it is necessary to proceed uniformly over the whole cross-sectional area and to
stop the averaging when the other end of the cross-sectional area is reached.
Alternatively, the average flow velocity can also be determined by single
net
measurements
according to VDI/VDE 2640 (s. 10.4.4 ) e.g. 13.24 m/s).
To display, output, and / or save the number of measuring operations
a special function channel
'n(t)'
is available; (see 11.3.9).
With Pitot tubes, in order to calculate actual velocity, both temperature compen-
sation and atmospheric pressure compensation are required; (see 10.2.5,
10.2.6).
The average velocity
is displayed in function:
Average value: 13.24m¡
Input of the diameter in mm (max. 4000):
Diameter: 0150 mm
Input of the cross section area CS directly in cm
2
:
CrossSection: 0175c¥
Display of the volume flow VF
in a function
Volume flow:
channel
in m
3
/h:
11: 834.¦¢
Output of all function values of the menu by using:
<PRINT>
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 so ´#N´ must be programmed in the designation either in the speed
channel or in the volume flow channel only; (see 11.3.2); this automatically pro-
duces the standard volume flow.
C © REC COM l© ©l R01 * ´´´´´´µµµµ¶
±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±
01: 11.67 mls Volocity
|¹¹¹¹¹¹¹¹¹¸¹¹¹¹¹¹¹¹¹¸¹¹¹¹¹¹¹¹¹¸¹¹¹¹¹¹¹¹¹¸¹¹¹¹¹¹¹¹¹|¹¹¹¹¹¹¹¹¹¸¹¹¹¹¹¹®®®¸®®®®®®®®®¸®®®®®®®®®¸®®®®®®®®®|
5.00 S220 mls 15.00
Damping:
20
Averaging mode:
CONT
Average value:
13.24 mls
Counts:
12
Volume flow:
11: 8343. m
3
/h
Diameter:
150 mm
Cross section:
175 c¥
START MANU M PRINT ESC
