BERTHOLD TECHNOLOGIES LB 567, User Manual

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Chapter 3. System Description
16 MicroPolar 2 (++) LB 567
3.2
Calculation of Measured Values
The microwave parameters phase and attenuation are calibrated
according to an automatic plausibility analysis.
During calibration, the phase and/or attenuation of a concentra-
tion value (or density value) are assigned through sampling. The
calibration is done automatically and the sampling process is sup-
ported by the evaluation unit.
Which of the parameters (phase, attenuation or both) will be used
for the calibration depends on the size and interference of the
measuring effect. For example, the attenuation is significantly
more sensitive to electrolytic conductivity (salt content).
In many cases, the pure phase measurement is recommended
and the measured value is calculated as follows:
Measured value = A ∙ Phase + C Eq. 3-1
where:
Measured value Concentration / Moisture / Dry matter
A, C Coefficients of the respective calibration function
The LB 567 allows you to calibrate, display and output two con-
centrations: Con1 and Con2. You have to enter the calibration
coefficients separately for concentration 1 and 2. For more infor-
mation please refer to the Software Manual.
Limitations
Weakly bound water can be detected depending on the
strength of the binding. Thus, the measuring effect may be
dependent on the grain size distribution and the chemical
properties of the product being measured, provided this
changes the binding of water to the solid matter.
Walls made of plastic, rubber or insulation materials with fairly
low dielectricity hardly affect the measurement and are cali-
brated at a constant level.
Ice and crystal water cannot be measured because the water
molecules cannot rotate freely (ice and crystal water are dry).
Conductive materials such as graphite or coke cannot be trans-
mitted by microwaves. Metal walls can also not be transmitted by
microwaves. Metal-reinforced conveyor belts may be transmitted
only under certain conditions (see
chapters 4.3.3 Installing the
Horn Antenna ).