Hi
I'm working on a water sensor
The application is a pump which has a metallic surface connected to the earth wire. The sensor consists of a metal plate housed in a plastic enclousure mounted on the chassis of the pump. The capacitance measured is the one from the metal plate to the chassis - growing in value when the water is present. The sensor plate is in direct contact with the water
So with pure or low contaminated water we measure the capacitance between the electrodes taking advantage of the dielectric constant of
80 for water.When the water is polluted or is a salt solution we measure the conductance of the water
But, I'm searching for theory/documentation for the conductance of water with a salt solution at different frequencies. I have measured the conductance using a network analyzer and have found that it seems the conductance is lower at higher frequencies. So it seems at very high frequencies (300MHz) the water begins to act as a capacitance again without significant conductance.
But I want to be sure and don't want to measure all kinds of extremes. So does anyone know of theory/books/links to descriptions of the properties of water? (conductance, dielectric value etc)
Thanks
Klaus