I had an idea of how to measure the back and forth frequency of the water...
The idea is simple... It consists in an electrolytic cell having two parallel plates gap variable, having special made coil around the cell. The coil will capture the magnetic field derived from the ions movement. A square wave is applied to the cell and the voltage reading across the coil could be interpreted as the ions movement. As the ions are positive and negative they should create a magnetic field that adds up since they are accelerated in different directions. The output wave form will tell about the ions movement if not also extract energy from the electric field itself...
The ions will have a certain speed limit just like a skydiver have limit speed. So the results could become contradicting as constantly moving ions only create magnetic field that is not varying except by its motion! However is a start point.
The analysis must be focused on the electric field force and ion charge mass relation and water density.
Motion can be implemented externally so easy measurements can be done.
The coil could be done following the electric field and when it need to return against the magnetic field it should be more perpendicular... This will raise the chance to capture a signal.