Fill level sensor prototype photos

sensor prototype

Now we can take a closer look at hardware part. It's very simple: two aluminum tubes with plastic spacer on one side. Outer tube grounded, inner wired through spacer by small hole, tight sealed with wire. Spacer must be fully hermetical, especially if  you intends to work with flammable or easy evaporated fluids like gasoline.
Why gasoline? Because it most complicated fluid for capacitive measurements. Gasoline has very low permittivity close to 2 (it means 40 times less than water). Low permittivity leads to low spread of capacitances. It means that filled sensor will have only twice more capacitance than dry one. Literally, we need to measure spread between 20 and 40pF. And sensor copes with it pretty well, shows only 2.5% nonlinearity. It means that kind of sensor can be used for most hard tasks like any types of fuel, refrigerants or even liquid gases.