Emerson Rosemount Apex, Reference Manual

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Reference Manual
00809-0100-4731, Rev FA
April 2003
1-3
APEX
™
and APEX Sentry
™
Radar Gauge
OVERVIEW
The APEX and APEX Sentry Radar Gauges use a radar signal to measure
the level of liquid in a vessel. Because the radar gauge is mounted on top of a
vessel and its components do not contact the product, it is a dependable
alternative to a standard insertion device that can become broken or corroded
when inserted into the process. The APEX Radar Gauge also works well in
turbulent, aerated, solids-laden, viscous, or corrosive liquids, and thick pastes
or slurries.
The advanced 24 GHz frequency technology in the gauges significantly
increases the reliability of your level measurement for a wide range of tank
level applications. The gauges use radar technology based on frequency
modulated continuous wave (FMCW) transmission of microwaves. Radar
(microwave) signals are sent from the gauge to the surface of the material
and reflected back to the gauge receiver. The receiver evaluates the
frequency difference between the transmitted and returned signals. The
gauge analyzes the signals to determine the distance to the product surface.
The 24 GHz frequency and advanced electronics allow the radar gauges to
use a small antenna and maintain a narrow beamwidth. The small, lightweight
antenna simplifies installation while the narrow beamwidth allows unwanted
echoes from vessel obstructions such as agitators, heat exchangers, filling
pipes, baffles, thermowells, and intermittent filling streams to be avoided. The
narrow beam also increases mounting flexibility because the gauge can be
mounted on existing flanges located close to tank walls.