Appendix D: Technical Reference; Principles Of Operation; Process Variables - Siemens SITRANS LR560 Operating Instructions Manual

Appendix D: Technical Reference

Note:
Where the number follows the parameter name [for example, Algorithm (2.4.5.1.)]
this is the parameter access number via the handheld programmer. See
Reference on page 86

Principles of Operation

SITRANS LR560 is a 2-wire 78 GHz FMCW radar level transmitter for continuous
monitoring of solids in vessels
principle to determine distance to a material surface.
FMCW radar transmits a continuous wave. The frequency of the wave is constantly
increasing: this is known as the sweep. By the time the first part of the wave has been
reflected off the target and returned to the device, the part of the wave that is just being
emitted is at a higher frequency. The difference in frequency between the transmitted and
received signals is proportional to time of flight.
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 LR560 consists of an enclosed electronic circuit coupled to an antenna and
process connection. The electronic circuit generates a radar signal (78 GHz) 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 sensor
2)
reference point
calculating the display of material level.

Process Variables

The Process Variables are sensor value and measured value. Sensor value is the
distance from the sensor reference point (flange face) to the material surface. Since
LR560 does not support Volume, the Measured value can be either Level (distance from
low calibration point to material surface), or Distance (distance from sensor reference
point to the material surface).
1)
The microwave output level is significantly less than that emitted from cellular phones.
2)
Dimensions
See
7ML19985LY01
for a complete list of parameters.
1)
. Radar level measurement uses the time of flight
to the material surface. This value (sensor value) is used as a basis for
on page 12.
SITRANS LR560 (FF) – INSTRUCTION MANUAL
Parameter
Page 137