I need to measure the level of water inside a tank with a plastic wall about 5mm thick, but since this is just an hobby project I'm in no hurry. I will use a capacitance sensor to detect the water level in a non invasive way, since the water is ultra-pure so I don't want to put any sensors inside the tank.
Water has a high dielectric constant, so it should be easily detected by this method.
I want to use the charge transfer method, like QTouch does, but I don't want to use the library, I don't like the opacity of everything QTouch related, especially those AVR chips that have QTouch peripherals with undocumented interfaces. C'mon, is a touch interface really such a big deal it has to be kept under such secrecy? Please...
Well, sorry for the rant.
I will follow the info in the World version of the QTouch patent, WO0031553 (A1), and this document from Cypress. I also read this thread, seems the poster got it but was afraid to post the code because QTouch is patented.
Should I care about that, since the patent has lapsed in my country and in most of Europe?
Has anyone implemented this method without the QTouch library and could share some useful links?
Regarding the sensor, what shape should it have for best sensitivity? It needs immunity from people moving near the tank.
Finally, here is a pic from the patent, showing exactly what I want to do: