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 mm 2 . The proposed chip is suitable for devices of measuring liquid level, such as device of detecting liquid level of intravenous drip.

In this paper, a calibrated liquid level sensor transducer for detecting rainfall of botanic garden is newly proposed. The output signal is a pulse stream, it could be easily sent over a wide range of transmission media, such as package switch network, radio, optical, infrared, ultrasonic, and so on. Another innovation is that a calibration method is proposed to easily adjust parameters to calibrate various liquid level sensors. By collocating with a liquid level sensor that has a range of 3.97 to 123.34 mm, the corresponding output frequency ranges from 3.12 to 57.25 kHz. After calibration, the measured maximum frequency error is 1.46%. Measurement results have successfully verified all the functions and performance of the proposed calibrated liquid level sensor transducer and confirmed it to be applied on detecting rainfall of botanic garden. The proposed calibrated liquid level sensor transducer is suitable for devices of detecting liquid level.Index Terms-Rainfall, liquid level sensor, liquid level sensor transducer.