VEGA VEGAPULS 51K…54K 4 … 20 mA; HART compact sensor - Manual (Page 4)

4 VEGAPULS 51K … 54K
21750-EN-031222
Product description
emission - reflection - reception
Meas.
distance
1 Product description
1.1 Function
Ra dio d etecting a nd r anging: Radar.
VEGAPULS radar sensors are used for non-
contact, continuous distance measurement.
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 pulses. 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.
The radar pulses are emitted by the antenna
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 a re-
ceiver. Signal running periods of less than
one billionth of a second must be processed
and the echo image evaluated in a fraction of
a second.
1 ns
278 ns
Pulse sequence
VEGAPULS radar sensors can achieve this
through a special time transformation proce-
dure which spreads out the more than 3.6
million echo images per second into a quasi
slow-motion picture, then freezes and proc-
esses them.
t t
Time transformation
Hence, it is possible for the radar sensors to
process the slow-motion pictures of the sen-
sor 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.