The work described consists of investigating an entirely novel technique for measuring the velocity of the flowing components in vertically upward, gas/liquid flows in the “Cap bubble” and “Taylor bubble” flow regimes. The technique consists of mounting an array of 64 axially separated conductivity sensors in a vertical pipe through which an air/water mixture is flowing (water is the continuous component). By cross-correlating the output signals from any two of these conductivity sensors it is possible to obtain the mean Cap bubble (or Taylor bubble) velocity and hence an estimate of the mean gas velocity. The novel element of the work is to demonstrate that by appropriately combining the output signals from the array of 64 conductivity sensors it is possible to determine the output signals that would be obtained from one or more “simulated impedance sensors” that are travelling through the flow at the same speed as the Cap bubbles (or Taylor bubbles). Cross-correlation of the outputs from two of these simulated conductivity sensors, travelling in between the Cap bubbles, allows the liquid velocity relative to these moving sensors to be determined. Since the velocity of the simulated sensors is known, the liquid velocity can be determined. (4 pages)