MMP20 SONO-DIS (option D)
Page 22
Hauser
9
Working with the SONO-WZ probe
Introduction
SONO-WZ
uses cutting edge radar technology at 1 gigahertz and a probe whose measuring
field penetrates deep into the material to be measured. Plastic and liquid fresh concretes with
a consistence class of F2 to F6 can be measured by hand easily and directly with SONO-WZ.
An automatic averaging function when 4-10 single measurements are taken ensures a
representative measurement of the material mix. Thanks to the structured measurement method,
representative and precise measurement results are displayed within a few minutes.
SONO-WZ
uses the innovative TRIME TDR technology (
T
ime-
D
omain-
R
eflectometry) based on
guided radar waves. Very low-power (10 mW) radar waves (i.e. no potential risk from
electromagnetic radiation etc.) are also used in industrial level measurement. In the TDR
measurement method based on TRIME technology, the radar pulse is attenuated based on the
cement content and type. The EC
TRIME
conductance value in dS/m (decisiemens per meter) is then
used for the assessment of the cement.
Please note:
The measured value can fluctuate considerably in the case of concretes that do not
meet the specifications of DIN EN 206-1 and DIN 1045-2 (e.g. concretes that tend to bleed).
Incorrectly mixed concretes are difficult to measure with the SONO-WZ (but also with the
kiln-drying test)!
Measurement volume of the SONO-WZ probe
In theory, the electromagnetic field lines penetrate the material
to be measured to an infinite depth. However, the SONO-WZ
probes' effective penetration depth, which is relevant for
measurement, is max. 5 cm around the probe surface at the dark
ceramic plate. The field lines around the probe are illustrated in
green in the graphic.
With regard to the intensity of the measuring field, it is
important to consider that in all dielectric measurement
methods, such as TDR, microwave and the capacitance method,
the field line distribution is exponential rather than linear. This
means that the field is most intense directly at the probe in all
the measurement methods, and decreases exponentially the
further the measurement is from the probe head. This is a law of
physics and (unfortunately) cannot be altered by modifications to
the probe design. The consequence for moisture probes is that
larger gravel pieces located directly at the probe head can falsify
a reading. For this reason, moisture probes used in concrete
mixers, for example, average and filter several individual
measurements to achieve an accuracy of +-1.5 liters per m
3
with
the
SONO-MIX
mixer probe for instance. Just like the
application in a mixer, when using the SONO-WZ it is important to consider that larger gravel pieces
located directly at the probe head can falsify a reading. Therefore, when taking measurements with
SONO-WZ the priority is to alter the bedding conditions of sand, cement and large gravel pieces so
that a representative material mix is obtained with several single measurements. This is achieved by
taking several individual measurements with different bedding conditions around the probe head.
