Design of a low cost signal conditioning circuit for self-compensated non contact capacitive type multi threshold liquid level sensor

A novel technique to design a reliable signal conditioning circuit (SCC) for self-compensating capacitive sensor meant for multi threshold liquid level measurements is presented in this paper. The non-contact type sensor for the measurement and control of liquid level is the key to avoid the corrosion of contact sensors due to chemicals and the usage of compensation system. The proposed capacitive, non-contact type sensor employs self-compensation technique whose output is of the order of Pico Farads, which is difficult to process for further control action. To overcome this, it is proposed here to design a reliable and precise signal conditioning circuit. Also, an efficient SCC is developed using Linear OPAMP. Experimental results reveal that the resolution of measurement of liquid level is improved with respect to electrode dimensions and the designed SCC converts the low capacitance output in a significant manner.