Sitron SLU, Installation Manual, Page: 6 / 24

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Fig. 9: Foam on the surface
Fig. 10: Moderately stirred
surface
Fig. 11: Intensely stirred surface
Obr. 12a: Short guide tube
installation
ventilation
holes
sleeves for
mounting
Obr. 12b: Total guide tube
installation
6
During filling, mixing and other processes, foam can develop on the
surface level of the measured liquid. The foam may considerably
absorb the ultrasonic signal which might cause malfunction or
inaccurate reading by the level meter.
(Fig.9). For such cases, it is necessary to set up " S E N S I T I V I T Y "
mode to "high" or contact Sitron for further consultation.
In case of a thin layer of foam, it is also possible to use the directional
horn for improving receipt of the reflected echo.
Scattering or attenuation of the ultrasonic signal can result if the surface
level has been moderately stirred or rippled (by a mixer, coming liquid
etc.). It can result in reduction of the measurement range or unreliable
function of the level meter (Fig.10).
Rotating mixer blades will cause surface agitation, which may result
in false reflections of the ultrasonic signal from the surface level and
unreliable operation of the level meter (Fig.13).(obr.11). For
a rippled or swirling level, you can use the directional
horn to eliminate scattering of the ultrasonic signal.
If the level sensor is mounted to bottlenecks and places with
barriers, or near uneven walls or the filling area, where the
transmission signal could be distorted, we recommend using a
guide tube (acoustic horn). The tube must be made from a single
material with a smooth inner surface (see image 12a, 12b). The
minimum tube diameter must have the dimension "b" according
to image 4 on page 5. After installing, you must perform the
procedure "TEACHING". We recommend consulting with the
Sitron on the construction of the guide tube.
Installation Manual