A CMOS liquid level to frequency converter with calibration circuits for detecting liquid level of intravenous drip

In this paper, a CMOS liquid level to frequency converter with calibration circuits for detecting liquid level of intravenous drip is newly proposed. A calibration technique is proposed in the work. Another innovation is that the outputs of the proposed chip are directly digitized, they could be easily sent over a wide range of transmission media, such as PSN, radio, optical, IR, ultrasonic, and etc. Before performing the proposed calibration circuits, the maximum linear error is 46.44% After calibration, the maximum linear error is reduced to 2.04% The liquid level range is 32 steps, and the corresponding output frequency range is 3.14 to 58.14 kHz. The chip area is 2 × 1.96 mm². The proposed chip is suitable for devices of measuring liquid level, such as device of detecting liquid level of intravenous drip.