A conductivity‐type local void measurement system has been developed. The effects of the sensor tip geometry, the unbalance of the front‐end bridge, the comparator threshold level, and the mass fluxes on the response of the instrument have been studied. The system has been calibrated under air–water two‐phase flow conditions using the quick‐closing‐valve technique. Comparison of the void profiles obtained with the conductivity probe with those obtained using an optical probe confirms the applicability of this system for two‐phase (air–water) flows.