Differential Pressure Sensing Based on Phase Sensitive Detection for Liquid Level Measurement

In this paper, a capacitive differential pressure sensor is characterized as a liquid level measurement system. The sensor is configured as a first-order low pass filter with a cut off frequency at 10 kHz, driven by a sinusoidal signal at 100 kHz. The phase-sensitive demodulation of the signal is performed using a single-tone DFT algorithm, acquiring both excitation and output signals. Each signal is acquired at 10 MSPS and the DFT is computed on 8000 samples. The sensitivity of the proposed instrument is 40 ppm/mm with very good linearity and error as low as +/- 0.3 mm. The measurement characterization of the sensor indicates good performances as low-cost level measurement system.