54733-10BA2L
1 – 96 02.2017
7 Functional Safety Volume 1
7.5.1.3 Density measurement
The measuring system consists of a detector and a radiation source.
These are mechanically positioned such that the beam path runs
through the product in order to detect the product density. The
safety function is to monitor the fill level of the product to be mon-
itored within a defined density measuring range.
Principle of measurement A higher product density reduces the radiation intensity at the
detector. A lower product density increases the radiation intensity
at the detector. The change in radiation intensity is output in the
detector as a continuous signal within the measurement range.
The detector signals the change in density via the analog current
signal. The lower measuring range of the density corresponds to
4mA, the upper range corresponds to 20mA. The PT100 may be
used for temperature compensation.
Signal
"1.2g/cm
3
"
Shielding with
radiation source
Shielding with
radiation source
Radiation path
Pipeline
Pipeline
Detector
Detector
Signal
"1.0g/cm
3
"
Radiation path
Product density "A"
e.g. 1.0 g/cm
3
Product density "B"
e.g. 1.2 g/cm
3
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