User Manual

8 VEGAPULS 42 and 44 – 4 … 20 mA
Reflected radar power dependent on the dielectric
constant of the measured product
2
0
0
10
25 %
40 %
5
10
5 %
20
30
40
50
%
4 6 8 12 14 16 18
20
r
t
t
1 ns
278 ns
Time transformation
Pulse sequence
Product description
The radar impulses are emitted by the an-
tenna system as pulse packages with a
pulse duration of 1 ns and pulse intervals of
278 ns; this corresponds to a pulse package
frequency of 3.6 MHz. In the impulse inter-
vals, the antenna system operates as re-
ceiver. Signal running periods of less than
one billionth of a second must be processed
and the echo image must be evaluated in a
fraction of a second.
All products which are electrically conductive
reflect radar signals very well. Even slightly
conductive products ensure a sufficient re-
flection for a reliable measurement.
All products with a dielectric constant e
r
of
more than 2.0 reflect radar impulses suffi-
ciently (note: air has a dielectric constant e
r
of
1).
The signal reflection increases with the con-
ductivity or with the dielectric constant of the
product. Hence, virtually all products can be
measured.
With standard flanges of DN 50 to DN 250,
ANSI 2“ to ANSI 10“ or G 1
1
/
2
A and 1
1
/
2
“ NPT,
the sensor antenna systems can be adapted
to the various measured products and meas-
urement environments.
The high-quality materials can also withstand
extreme chemical and physical conditions.
The sensors deliver a stable, reproducible
analogue or digital level signal with reliability
and precision, and have a long useful life.
VEGAPULS radar sensors can accomplish
this through a special time transformation
procedure which spreads out the more than
3.6 million echo images per second in a slow-
motion picture, then freezes and processes
them.
Hence, it is possible for the VEGAPULS 40
radar sensors to process the slow-motion
pictures of the sensor environment precisely
and in detail in cycles of 0.5 to 1 second
without using time-consuming frequency
analysis (e.g. FMCW, required by other radar
techniques).
Virtually all products can be measured
Radar signals display physical properties
similar to those of visible light. According to
the quantum theory, they propagate through
empty space. Hence, they are not depend-
ent on a conductive medium (as e.g. sound
waves in air), and spread out like light at the
speed of light. Radar signals react to two
basic electrical properties:
- the electrical conductivity of a substance
- the dielectric constant of a substance.