A multi-phase converter has a plurality of switching circuits each controlled by a phase controller and each providing a switched output voltage to an output node of the converter. The toilet is flushed, the actuator lever opens the flo-control valve stopper by means of linkage to the flush lever. The oscillations or waves may be caused from longitudinal, shear, andor Raleigh waves in the object to be tested. Next, the determined value is used to determine a churn value. Finally, the control unit verifies whether the provided signal corresponds to a signal expected by the control unit.