Appendix A: Technical Reference; Principles Of Operation; Measurement Response - Siemens SITRANS LR460 HART Operating Instructions Manual

Appendix A: Technical Reference

Principles of Operation
SITRANS LR460 is a long range FMCW (Frequency Modulated Continuous Wave) radar
transmitter. Radar level measurement uses the time of flight 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 or dust levels inside a vessel.
SITRANS LR460 consists of an enclosed electronic component coupled to an antenna
and process connection. The electronic component generates an electromagnetic signal
from 24.2 GHz to 25.2 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 material
surface to the reference point on the instrument. This distance is used as a basis for the
display of material level and output.

Measurement Response

The measurement response (response rate) limits the maximum rate at which the
display and output respond to changes in the measurement. Once the real process fill/
empty rate (m/s) is established, a response rate can be selected that is slightly higher
than the application rate. The response rate automatically adjusts the filters that affect
the output response rate.
There are three preset options: slow, medium, and fast.
Related
Parameters
Values
If none of the preset options is satisfactory, the filters can be adjusted individually.
A5E42035355
Response LOE Timer
Rate (minutes)
* slow
medium
fast
SITRANS LR460 – INSTRUCTION MANUAL
Fill Rate
100 0.1 m/minute
10 1 m/minute
1 10 m/minute
Empty Rate
0.1 m/minute
1 m/minute
10 m/minute
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