Flow velocity meter having signal generating module with phase locked loop for generating continuous wave signal

A flow velocity meter is disclosed. The flow velocity meter utilizes a phase locked loop to generate an output signal and outputs the output signal to a current under test. The flow velocity meter receives a reflection signal from the current under test to calculate a speed of the current under test according to a reflection signal and a frequency difference between the output signal and the reflection signal. The flow velocity meter further includes an inclinometer for measuring a depression angle between a water level and a normal direction of the flow velocity meter and measuring a horizontal angle. The flow velocity meter can be adjusted its orientation when being installed according to the measured angles.