SITRANS LR200 with mA/HART
Operating Instructions, 05/2019, A5E32337676-AE
171
Technical reference
B
Note
Where a number follows the parameter name [for example, Master Reset (4.1.)] this is the
parameter access number via the handheld programmer. See Parameter Reference
(Page 97) for a complete list of parameters.
B.1
Principles of operation
SITRANS LR200 is a 2-wire 6 GHz pulse radar level transmitter for continuous monitoring of
liquids and slurries
1)
. Radar level measurement uses the time of flight principle to determine
distance to a material surface. The device transmits a signal and waits for the return echo.
The transit time is directly proportional to the distance from the material.
Pulse radar uses polarized electromagnetic waves. Microwave pulses are emitted from the
antenna at a fixed repetition rate, and reflect off the interface between two materials with
different dielectric constants (the atmosphere and the material being monitored).
Electromagnetic wave propagation is virtually unaffected by temperature or pressure
changes, or by changes in the vapor levels inside a vessel. Electromagnetic waves are not
attenuated by dust.
SITRANS LR200 consists of an enclosed electronic circuit coupled to an antenna and
process connection. The electronic circuit generates a radar signal that is directed to the
antenna. The signal is emitted from the antenna, and the reflected echoes are digitally
converted to an echo profile. The profile is analyzed to determine the distance from the
material surface to the sensor reference point
2)
. This distance is used as a basis for the
display of material level and mA output.
1)
The microwave output level is significantly less than that emitted from cellular phones.
2)
Refer to Dimension drawing (Page 152).
B.2
Echo processing
B.2.1
Process Intelligence
The signal processing technology embedded in Siemens radar level devices is known as
Process Intelligence.
Process intelligence provides high measurement reliability regardless of the dynamically
changing conditions within the vessel being monitored. The embedded Process Intelligence
dynamically adjusts to the constantly changing material surfaces within these vessels.
Process Intelligence is able to differentiate between the true microwave reflections from the
surface of the material and unwanted reflections being returned from obstructions such as
seam welds or supports within a vessel. The result is repeatable, fast and reliable
measurement. This technology was developed as result of field data gained over some
twenty years from more than 1,000,000 installations in many industries around the world.
