Liquid level using capacitive sensors

[iykedapotential]

Hi,
I am dong a project on liquid level using capacitive sensors. I need help on how to go about it and also to connect it to a microcontroller that will display the depth of the liquid in an LCD. the major problem is the calibration.

thanks.

 

[jiripolivka]

The first condition is that the sensed liquid must be low-conductivity so only the capacitance is varying.
The sensing capacitor is made as two parallel electrodes, strips or wires.
The calibration is done with a particular liquid and level range using a capacitance meter.
Then you must make your capacitance meter that will output the analog data to your display.

Use an oscilloscope to measure the capacitance-meter test frequency, and design your sensing circuit for the same frequency.

The sensing circuit can use a pulse generator and audio voltmeter if you connect your sensing electrodes in a "voltage divider", so the output amplitude is driven by capacitance changes. You can use a DVM with AC Volts range for it.
Or you can use the sensing capacitor in a multivibrator, so its frequency will change with capacitance. Then you will need a counter or a frequency meter to read he result.

All above can be made a weekend project. Good luck!