VEGA VEGAPULS 56 Profibus PA - Manual (Page 25)

VEGAPULS 56 Profibus PA 25
Reference plane
Mounting on dished tank ends
Reference plane
1 /
2
vessel radius
Mounting and installation
Mounting directly on the flat vessel top
Sensor directly on the vessel top
If the stability of the vessel will allow it (sensor
weight), flat mounting directly on the vessel
top is a good and economical solution. The
top side of the vessel is the reference plane.
On dished tank ends, please do not mount
the instrument in the centre or close to the
vessel wall, but approx.
1 /
2
vessel radius from
the centre or from the vessel wall.
Dished tank ends can act as paraboloidal
reflectors. If the radar sensor is placed in the
focal point of the parabolic tank, the radar
sensor receives amplified false echoes. The
radar sensor should be mounted outside the
focal point. Parabolically amplified echoes are
thereby avoided.
Mounting on a dished vessel top
> 10 mm
3.3 Measurement in standpipe
(surge or bypass tube)
General instructions
Pipe antennas are preferred in vessels which
contain many installations, e.g. heating tubes,
heat exchangers or fast-running stirrers.
Measurement is then possible where the
product surface is very turbulent, and vessel
installations cannot cause false echoes.
Through focusing of the radar signal within
the measuring tube, even products with small
dielectric constants (
ε
r
= 1.6 up to 3) can be
reliably measured in surge or bypass tubes.
Please note the following instructions.
Surge pipes which are open at the bottom
must extend over the full measuring range
(i.e. down to 0% level), as a measurement is
only possible within the tube.
It is advantageous to install a deflector below
the end of the tube. The product can then be
reliably detected around the min. level. This is
particularly important for products with a
dielectric constant of less than 5.