Gebrauchsanweisung / Instructions for Use - SCHMIDT
®
Flow Sensor SS 20.225
15
3 Mounting instructions
General information on handling
The
SCHMIDT
®
Flow Sensor SS 20.250
is a precision instrument with
high measuring sensitivity. Therefore, avoid applying mechanical force to
the probe tip.
The protective cap should be place onto the sensor head every time the
sensor is handled mechanically (installation, dismounting, transport).
Avoid mechanical stress on the sensor head as best as possible
in to prevent irreversible damage.
Mounting position
The flow measuring sleeve (heater) must always be in the middle of the
flow channel to provide good measuring results.
The sensor must also necessarily detect
the temperature of the medium, i.e. the
temperature measuring sleeve must be in
direct contact with the medium (but not
with the wall). This results in a minimum
immersion depth MID = 58.5 mm (see right).
The sensor head (including its temperature measuring sleeve)
must be completely immersed in the air flow. If not, the measured
value can be strongly distorted.
To achieve the maximum measuring sensitivity, the sensor head should
be mounted pointing upwards or horizontally. A sensor head pointing
downwards should be avoided, because this increases the lower measur-
ing range limit (nominally 0.06 m/s).
The sensor should not be installed near heat sources as this may result in
measurement errors. Therefore, it should always be installed, for instance,
upstream of any heat exchanger that may be present.
Flow characteristics
To reach the accuracy specified in its data sheets, the sensor has to be
positioned in a straight conduit and at a place with undisturbed flow profile.
Correct measurements require laminar
12
flow with as low turbu-
lence as possible.
An undisturbed flow profile can be achieved if a sufficiently long distance
in front of the sensor (run-in distance L1) and behind the sensor (run-out
12
Here the term “laminar” means an air flow low in turbulence (not according to its physical
definition saying that the Reynolds number is < 2300.
Temperature measuring sleeve
Heater
9.3
MID
Ø
9
