AbstractA major challenge of prototype air-water flow measurement is the limited endurance of fragile phase-detection needle sensors in a high-momentum flow with risks of debris damage and particulate erosion. In the present study, a thick-tip conductivity probe is manufactured with sturdier needle sensors than the commonly used laboratory-sized probes. The large sensor tip had low chance to pierce small air bubbles and water droplets, leading to deterioration in the signal output quality, which prevents derivation of basic air-water flow properties using the conventional signal processing technique. To extract valid phase information from the low-quality signal, calibration experiments were conducted in laboratory with reference to a regular-sized probe, to explore a proper signal processing method for the thick-tip probe. The method was validated, and the thick-tip probe was deployed in a field hydraulic jump measurement, allowing for access to the air-water flow characteristics of the prototype D-type jump with a Reynolds number of 1.88×106. Despite the effort of signal calibration and compensation, the use of the thick-tip probe does not guarantee accurate bubble size measurement and requires higher sampling frequencies. Therefore, probes with fine sensor tips are still preferable in prototype measurement.