The SONARtrac clamp-on system provides a non-contact, on-line, real-time measurement of the volumetric flow and amount of entrained air/gas present in any liquid-continuous-phase process fluid. The system also provides a measurement of only the liquid portion of the flow by compensating for the amount of entrained gas/air in the process line. Insensitive to changes in magnetite density, the SONARtrac clamp-on system is completely immune to the magnetic properties of magnetite. It does not suffer from abrasive wear (compared with in-line devices) or signal attenuation (as in ultrasonics) associated with medium to high solids contents.