VEGA VEGAPULS 45 Profibus PA - Manual (Page 18)

18 VEGAPULS 42, 44 and 45 – Profibus PA
24908-EN-041227
Surge pipes which are open at the bottom
must extend over the full measuring range
(i.e. down to 0% level), as measurement is
only possible within the tube. The tube inner
diameter should be max. 100 mm or corre-
spond to the size of the antenna horn.
3.3 Measurement in standpipe
(surge or bypass tube)
General instructions
Measurement in a standpipe is preferred in
vessels which contain many installations, e.g.
heating tubes, heat exchangers or fast-run-
ning stirrers. Measurement is then possible
when the product surface is very turbulent,
and vessel installations can cause no false
echoes.
Due to the concentration of the radar signals
within the measuring tube, even products
with small dielectric constants (
ε
r
= 1.6 up to
3) can be reliably measured in surge or by-
pass tubes. Note the following instructions.
max max
min
min
Pipe antenna system in the tank
Type label
Vent hole
ø 5 … 10 mm
Surge pipe welded
to the tank Surge pipe in the
socket piece
without deflector with deflector
Rod antenna mounted directly in vessel opening
As an alternative to socket mounting, the
screwed antenna can also be mounted in
round vessel openings (threaded holes).
Mounting and installation
Screwed antenna with antenna extension on socket
piece
≤ 250 mm
Screwed antenna on 1½“ mounting boss
≤ 135 mm
Reference plane
Screwed antenna
The screwed antenna is used mainly on very
small vessels. The antenna fits into even the
smallest vessel connection openings (1
1 /
2
“
socket). The socket must not be longer than
135 mm (when using a longer antenna, not
longer than 250 mm).