VEGA VEGAPULS 51K…54K Profibus PA - Manual (Page 4)

4 VEGAPULS 51P … 54P
24890-EN-041227
Product description
t t
1 Product description
1.1 Function
Ra dio d etecting a nd r anging: Radar.
VEGAPULS radar sensors are used for non-
contact and continuous distance measure-
ment. The measured distance corresponds
to a filling height and is outputted as level.
Measuring principle:
emission – reflection – reception
Extremely small 5.8 GHz radar signals are
emitted from the antenna of the radar sensor
as short impulses. The radar pulses reflected
by the sensor environment and the product
are received by the antenna as radar ech-
oes. The running period of the radar pulses
from emission to reception is proportional to
the distance and hence to the level.
VEGAPULS can achieve this through a spe-
cial 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.
The radar pulses are emitted by the antenna
system as pulse packets with a pulse dura-
tion of 1 ns and pulse intervals of 278 ns; this
corresponds to a pulse package frequency
of 3.6 MHz. In the pulse intervals, the antenna
system operates as a receiver. Signal run-
ning periods of less than one billionth of a
second must be processed and the echo
image evaluated in a fraction of a second.
Hence, it is possible for the VEGAPULS 50
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 (air), and they
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.
1 ns
278 ns
Time transformation
Pulse sequence
Meas.
distance
emission - reflection - reception