54
Hotline: +49 2953 73-211
Fax: +49 2953 73-250
Wöhler DC 100
PRO
factor in Equation 7,1 (see Section 7). The device must not be tipped after
zeroing.
An overpressure at the socket marked with the
+ sign
and an underpressure
at the socket marked with the
– sign
causes a positive differential pressure
to be displayed (see also Figure 2.2). When the differential pressure exceeds
1200.0 Pa, the device automatically switches to the higher measuring range
up to 10000 Pa with a resolution of 1 Pa. When the value falls below 1100 Pa
in this measuring range, the display switches back to a resolution of 0.1 Pa.
3.3 Flow rate measurements based on Prandtl
The flow rate of air in m/s can be measured with a Prandtl’s tube. This mea-
surement is activated when the ± key is repeatedly pressed in the
Signal
menu until the text “Prandtl” or “Max precision Prandtl” appears with the unit
of measurement “m/s”. In max-precision mode the max-precision pressure
signal with 0.01 Pa resolution is used as
∆
P in Equation (3.1). This means
that a flow rate from 0.1 m/s can be detected. The smoothing effect can be
set with the ALPHA value in Equation 7.1.
The total pressure of the tube is connected to the + overpressure socket
and the static pressure to the – underpressure socket on the DC 100
PRO
(see
Figure 3.3). First of all the device must be “zeroed” in a medium at rest (
P=0
).
Then the probe is inserted into the gas or air flow, as parallel as possible and
with the tip facing the flow, and the measured values are read off. The current
flow rate v is automatically calculated with Equation (3.1). According to Equa-
tion (3.1) the air density
ρ
in Equation (3.2) depends in turn on the absolute
air pressure p
cur
and the current temperature
ϑ
act
The pitot factor S takes into
account the geometry of the used tube and can be set under the menu item
Setup —> Pitot factor
. It is 1.00 for tube type L and 0.93 for type S.
Equation. 3.1
Equation 3.2
3. Signal menu, 4-Pa-test
