Endress+Hauser Solitrend MMP40, Operating Instructions Manual

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Diagnostics and troubleshooting Solitrend MMP40
26 Hauser
9 Diagnostics and troubleshooting
9.1 Optimizing the material flow
For accurate measurement results, certain limits must be respected with regard to the
installation and environmental conditions, and the associated bulk density of the material
being measured. Furthermore, there must be a sufficiently thick layer of material covering
the sensor.
If the material flow is too fast, the level of material above the surface of the sensor can be
too low. A hopper chute with guide plates can concentrate and increase the level of
material above the sensor head. Ideally - particularly in the case of wet sand - the guide
plates have a PTFE coating so that no material can stick to them. The sensor requires a
layer of material of at least 35 mm. There are installations where the amount of material
is too low or too spread out to ensure sufficient material flow over the sensor. In such cases
it may be necessary to "concentrate" the material flow so that material accumulates above
the sensor as it flows. The diagram below shows an example of a possible unit where the
material is concentrated at the side of the sensor and above the sensor.
A0037430
 18 Example: "Concentration of material"
In addition, in the case of non-homogeneous material flow it is possible to use the filter
functions, with upper and lower limits, that are implemented in the sensor to filter out
"wrong" measured values.
9.2 Difference between measured moisture value and
laboratory value too large during initial
commissioning
The sensor is usually precalibrated with Cal14 (air/water 0 to 100 %) upon delivery. In the
case of sand and gravel applications, the sensor is precalibrated upon delivery (if the
application is known and specified beforehand) with the Cal1 calibration curve (universal
calibration curve for sand/gravel).
During initial commissioning, the measured moisture value should match the
laboratory value, which is determined using another method, with an accuracy of at
least +/-1 %.