This meter uses non-radioactive ultrasound to help municipal/industrial plants measure and monitor the density of primary, secondary, return-activated and backwash sludge/silt, in pipes, tanks and clarifiers—with no permits or approvals needed. Users can program underflow pumps to automatically shut off before sludge becomes too thin and helps determine flocculent dosages for improved filter press/centrifuge/digester performance, improving outflow available for reuse. Operators may also gain early awareness of breaks in filtration material. Readings are not affected by the color of particulates/fluid. The inline pipe spool-piece sensor is non-intrusive, and simple to install, calibrate and clean. A throw-in style probe is also available.