Endress+Hauser Solitrend MMP20, Operating Instructions Manual

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Solitrend MMP20 (Option D) SWZ probe
Hauser 25
8 SWZ probe
8.1 Introduction
The SWZ probe uses radar technology at 1 GHz and a probe whose measuring field
penetrates deep into the material to be measured. Plastic and liquid fresh concrete with a
consistence class of F2 to F6 can be measured by hand easily and directly. An automatic
averaging function, with 4 to 10 single measurements 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.
The probe uses TDR technology (Time-Domain-Reflectometry) based on guided radar
waves. Very low-power (only 10 mW) radar waves (i.e. no potential risk from
electromagnetic radiation etc.) are also used in industrial level measurement, for example.
In the measurement method, the radar pulse is attenuated based on the cement content
and type and used as an EC-T conductance value in dS/m (decisiemens per meter) for the
assessment of the cement.
Please note that the measured value can fluctuate considerably in the case of concrete
that does not meet the specifications of DIN EN 206-1 and DIN 1045-2 (e.g. concrete
that tends to bleed). Incorrectly mixed concretes are difficult to measure!
8.2 Measuring volume
A0040930
 15 Measuring field of the SWZ probe
In theory, the electromagnetic field lines penetrate the material to be measured to an
infinite depth. However, the probe's 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 the graphic. With regard to the intensity of the
measuring field, it is important to consider that in all dielectric measurement methods the
field line distribution is exponential rather than linear. This means that the field line is
most intense directly at the probe head in all the measurement methods, and decreases
exponentially the further the measurement is from the probe head. 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 l/m³ with the
mixer probe for instance. Just like the application in a mixer, when using the SWZ probe it
is important to consider that larger gravel pieces located directly at the probe head can
falsify a reading. Therefore, when taking measurements with the SWZ probe, 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 single measurements with different bedding conditions around the probe
head.