VEGA VEGAPULS 41 4 … 20 mA; HART compact sensor - Manual (Page 4)

4 VEGAPULS 41 – 4 … 20 mA
26620-EN-041227
Product description
1 Product description
Radar sensors usually come with horn or rod
antennas. PTFE rod antennas are suitable for
many applications with chemically aggres-
sive products, but are unsuitable for small
vessels due to their size. Also the reception
efficiency of the rod antenna is lower than that
of the (less resistant) horn antenna. The two
new radar sensors, VEGAPULS 43 with DN
50 and DN 80 process fittings and the de-
scribed VEGAPULS 41 with 1½“ process
fitting, perfectly round out the instrument
series. Horn and rod antennas that protrude
into the vessel belong to the past. The an-
tenna of VEGAPULS 41 consists of a small
40 mm TFM-PTFE cone that is suitable for
chemically aggressive environments. PTFE
has been known as the „Mercedes“ of plastic
materials for many years. They are resistant
to virtually all chemical media, such as e.g.
amines, ketones, esters, acids (sulphuric
acid, phosphoric acid, hydrochloric acid,
nitric acid), alkalis (caustic soda), oxidants,
fuels and oils. These plastics do not become
brittle or age and are suitable for tempera-
tures up to 150°C. The only limits to these
materials are applications with fluorine under
high pressure or with liquid alkali metals
(sodium or potassium), where adverse reac-
tions may occur. The cone acts like a lens
that focuses short (0.15 mW) radar pulses
into a beam and sends them towards the
product. During the pulse intervals, the
cones operate like a unidirectional micro-
phone with optimum reception efficiency. The
intelligent, extremely fast electronics converts
the radar echo into a precise image of the
environment and level, which is then
outputted as a 4 … 20 mA or Profibus signal. Due to their small housing dimensions and
process fittings, the compact sensors are
unobtrusive and, above all, cost-effective
monitors of your product levels. With their
integrated display, they enable high-
precision level measurements and can be
used for applications in which the
advantages of non-contact measurement
could never before be realized.
VEGAPULS radar sensors are perfectly
adapted to two-wire technology. The supply
voltage and the output signal are transmitted
via one two-wire cable. The instruments
produce an analogue 4 … 20 mA signal as
output, i.e. measuring signal.
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 26 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.