The new constructed logging tool is equipped with an injector enabling to create a colour mark in the streaming water. A pair of photometric sensors is located in the vertical distance 0.05 m and 0.1 m above and below the special outlet nozzle of the injector.
The probe is capable of measuring vertical flow velocities in the range 0.0001 - 0.01 m/s or vertical flow rates in the range of 0.001 – 0.1 l/s. The function of the tool was verified in the laboratory and in the borehole measurements.