Abstract: In order to increase the accuracy of frequency calculation for the density sensor based on the resonance theory, interpolated Fast Fourier Transform algorithm (FFT) algorithm which is based on the existing FFT and more adjusts the actual situation is introduced. The effect of frequency changes and the noise on results of frequency calculation is also analyzed. Comparative analysis for the commonly used windows is made through Matlab, and Rife_Vincent window is chosen finally. In addition, experiments have been carried out on the hardware system designed. The experimental results confirm that the calculation error is less than 0.1 Hz by means of the interpolated FFT algorithm with Rife_Vincent window. The results also test and verify that the method has very high accuracy and is easy to realize.

Key words: ⁺Liquid density measurement, Resonant sensor, Frequency calculation, FFT algorithm, ⁺Window function