Measuring method for the exact size of air bubbles in a liquid flowing through a hose and an electrode of a capacitance sensor and a capacitive sensor for carrying out of the measuring method

摘要

Before the medium is going to be pumped into the hose, this hose is placed between the sensing heads of the sensing electrodes of the capacity sensor of special design, which allows to measure only changes of permittivity of the environment inside the inserted hose. Physical qualities of each pumped medium are different, therefore it is necessary to calibrate the limit values of permittivity inside the pumping hose for specific conditions of pumping. This is achieved by repeated input and output of the pumped medium into the zone between the sensing heads of the capacity sensor, which results in obtaining statistically accurate values of permittivity of completely filled hose and permittivity of completely empty hose, however with wetted inner walls. Measured permittivity of pumped medium with however large air bubbles must lie between the limit values of calibrated permittivity. The pump's linear characteristics, in given case the unique relation of the angular displacement of the impeller to the volume of pumped-out medium, allow easy calculation of the size of possible air bubbles passing through the capacity sensor by means of linking-up the start and end of measured change of permittivity with the volume of pumped-out medium, i.e. with the angular displacement of the pump impeller.