Microwave and Radar Gauges

Microwave switches are beam-breaker-type point sensors with an accuracy of 13 mm (0.5 in.) and with pressure and temperature ratings up to 28 bar (400 psig) and 300°C (600°F). Pulse-type radar gauges have ranges up to 200 m (650 ft) and are accurate to 0.5% FS, whereas frequency-modulated carrier wave (FMCW) units have errors from 1 to 3 mm (0.04-0.125 in.). Their pressure and temperature ratings are up to 80 bar (1,200 psig) and up to 400°C (750°F). 

Frequency modulated carrier wave (FMCW) radar transmitters. (Courtesy of Thermo Measure Tech Inc.) 

The beam-breaker technique is useful for detecting large and abrasive materials such as coal, minerals, wood chips, and vegetable pulp. It is also useful for detecting very light materials such as dry sawdust and powdered materials in fluidized beds. This technique can also be considered for use on difficult-to-handle liquids that are viscous, toxic, or hazardous because the detector is isolated from the vessel contents. 

Post- Oil Energy Technology After the Age of Fossil Fuels 

FMCW radar level gauges are the primary tank farm radar devices because of the inherent accuracy. Pulse transmitters are not suitable for tank farm inventory and custody transfer applications. The combination of foam and low-dielectric material can cause errors or provide an insufficient signal strength on the return signal. 

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