Berthold LB 442, Operating Manual

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Section 2 System Description
9
The minus sign signifies that the intensity decreases as the load
increases. Apart from the constant factor, the initial intensity I
0
is
only affected by the product "roh
x
d", where "roh" is the density
of the conveyed material, i.e. the bulk density, and d the path cov-
ered by the radiation in the material.
If we multiply "roh x d", we get the mass per unit of area. This
variable is known as the weight per area and is assigned the unit
g/cm
2
.
The intensity of the radiation is therefore dependent upon
the height and bulk density of the material. The product of
height and bulk density is the weight per area!
If the mass per unit of area is now multiplied by the material
width, the result is the mass over 1 m of the conveyor; multiplica-
tion by the speed results in the desired mass per time unit, e.g.
tons per hour.
Contamination of the product being measured or the pipeline wall
by gamma radiation is not possible at all.
2.3 Measuring Configuration
To be able to cover a certain measuring range continuously, a
measuring configuration must be realized where the dimensions of
source and detector form an optimum geometry covering a meas-
uring field of equal size. The different options that are available
will be described below.
Which of these arrangements is chosen is dependent upon the
conveyor facility. Moreover, construction factors and customer-
specific requirements may have an effect on the instrument selec-
tion. The respective selections are made during the planning stage
and have to be taken into account later during assembly and
commissioning.
A measuring system for the radiometric bulk flow measurement
typically comprises the following components:
a) Radioactive rod source inside a:
b) Shielding container with holding device for detector:
- Measuring frame with shielding container (conveyor belt,
etc.) or
- Holding device with shielding for free fall measurement
c) Detector
d) Evaluation unit LB 442
e) Two-wire cable
f) Tachometer
(Option)
g) Cooling jacket for detector (option)