Measuring distance with microwaves

An FMCW radar sweeps its frequency continuously. The echo from the surface returns slightly delayed, so its frequency differs from the transmitted signal. That difference is proportional to distance, and subtracting it from the tank height gives level.

Why 80 GHz

Higher frequency allows a narrower beam, so the signal passes close to nozzles and agitators and gives a cleaner echo from small surfaces. Antenna sizes shrink, and the lens can be fully sealed in PTFE.

Limits

Very low-dielectric media, heavy foam and thick condensate can weaken the echo. In those cases a guided-wave probe, which carries the signal along a rod or cable, is the safer choice.