In addition, entrained air bubbles in slurry streams can lead to significant inaccuracies in density measurements thus leading to appreciable offsets in mass balance calculations. Besides measuring flow from the outside of the pipe, the array based technology has demonstrated the ability to measure the volume of entrained air bubbles in a slurry stream. This information has been used to compensate the density measurement from a nuclear density gauge thus enabling the accurate calculation of true mass flow rates. The principle of operation of this technology, the use of both flow and entrained air measurements to determine true mass flow rates will be detailed. Case studies of applying this technology to minerals processing operations will be discussed.