04/03 347 LB 444
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5.2.5 Installation of Resistance Thermometer Pt 100
A temperature measurement must be carried out such that the measured temperature is
fairly equal to the product temperature at the density measuring location.
The resistance thermometer must not obstruct the path of radiation.
If the resistance thermometer cannot be installed in the pipeline, it may also be mounted
on the outside of the pipeline.
This type of installation requires that the pipeline including the resistance thermometer
must be provided with temperature insulation over a length of 1 - 2 m, ensuring that the
surface temperature of the pipeline at the temperature measuring point is practically
equal to the product temperature. Nevertheless, it may happen, particularly with plastic
or coated pipelines that very sudden temperature changes in the product to be measured
will lead to measuring errors caused by the temperature. Density changes are detected
by the measurement immediately; however, the necessary temperature correction is de-
layed due to the inertia of the temperature measurement. Operating the system with a
rather large time constant may reduce this effect.
Before connecting the resistance thermometer to the detector, a Pt 100 adjustment has
to be performed in the Service menu (see chapter 6 GETTING STARTED).
5.2.6 Installation of Evaluation Unit
When installing the evaluation unit, please keep in mind:
In accordance with explosion protection criteria, the evaluation unit must only be used
outside the explosion protected area. If the evaluation unit - detector system is used in
accordance with fail-safe criteria, equipotential bonding has to be established between
detector and evaluation unit.
Max. permissible ambient temperature for the evaluation unit
Installation in 19” frame 50°C
Installation in wall housing with 1 evaluation unit LB 444 45 °C
Installation in wall housing with 2 evaluation units LB 444 40°C
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