Development and Calibration of a Resistivity Probe for Measurement of Air Concentration and Bubble Count in High-Speed Air - Water Flows

In this paper, the development of a resistivity probe for measurement of air concentration and bubble count in high-speed air water flow is described. One advantage of this type of probe is in its ability for real time measurement. The sampling frequency of the new probe is increased up to 250 kHz with 72 seconds sampling time. Polarization of the probe tip was noticed in this research work and the probe circuit was designed to avoid it. Sensitive microampere meters were installed on the probe to detect possible weak leakage currents. Electronic tests were performed to check the probe circuit, as well as more than 30 laboratory tests in air-water flow to set the threshold voltage of the probe circuit and to test its accuracy.