Design of a capacitive liquidometer applied in automobile

The measurement methods of liquid level are summarized. A cylindrical tube capacitive liquidometer consisting of two tubes is produced. Arithmetic relationship between the liquid level and the capacitance is derived. AD7746 is used to convert the capacitance signal into voltage signal. The voltage signal is then processed by PIC16F877 microcontroller and digitally displayed by the circuit of 1602. It is stated that sensor errors lie in manufacture, structure, and liquid temperature changes. The corresponding solutions are put forward. The calibration is carried out on the instrument to compare the values of the standard capacitance and calculated capacitance and test results are given.