Appendix D: Technical Reference; Principles Of Operation; Echo Processing; Process Intelligence - Siemens SITRANS LR250 Operating Instructions Manual

Appendix D: Technical Reference

Note:
Where the number follows the parameter name [for example, Algorithm (2.5.7.1.)]
this is the parameter access number via the handheld programmer. See
Reference (LUI) on page 96

Principles of Operation

SITRANS LR250 is a 2-wire 25 GHz pulse radar level transmitter for continuous monitoring
of liquids and slurries
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 LR250 consists of an enclosed electronic circuit coupled to an antenna and
process connection. The electronic circuit generates a radar signal (25 GHz) that is
directed to the horn.
The signal is emitted from the horn, 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
level.

Echo Processing

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.
1)
The microwave output level is significantly less than that emitted from cellular
phones.
2)
Threaded Horn Antenna with extension
See
13.
7ML19985KL01
for a complete list of parameters.
1)
. Radar level measurement uses the time of flight principle to
2)
. This distance is used as a basis for the display of material
SITRANS LR250 (FF) – OPERATING INSTRUCTIONS
Flanged Horn
on page 12 and
Parameter
on page
Page 145