Hach-Lange SONATAX sc - Manual (Page 9)

9
General information
2.4 Functional principle
In a tank where solid materials in water (or another fluid) can settle
to the bottom, there is a boundary between the settled solids and
the clear phase above. The distance from the water surface to the
bottom is the sludge level. The sludge height is the distance from
the tank floor.
More precisely, the sludge level (or the sludge height) indicates the
place in a tank where (viewed from the water surface) the solid
content first exceeds a defined limit. This limit value depends on the
application. It will, for example, be higher in a pre-thickener of a
wastewater treatment plant than in its final sedimentation, where
the overlying fluid should be clear water.
The SONATAX sc measures the sludge level via an echo signal
(refer to
Figure 2 ) of an ultrasonic pulse. This echo signal is shown
in the probe menu SENSOR SETUP > TEST / MAINT > SIGNALS
in the echo list (refer to
ECHO LIST on page 26 ). The depth and the
echo strength are specified at the ultrasonic transducer in digits
(1 digit approximately 1 µV).
Echos from layers that are further away are quieter (weaker) than
those which are closer. The SONATAX sc compensates for this
attenuation. The result is indicated on the SONATAX sc as a profile.
The data is found in the probe menu SENSOR SETUP > TEST /
MAINT > SIGNALS in the profile list (refer to
PROFILE LIST on
Figure 2 Functional principle