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A Novel Signal Processing Method Based on Cross-correlation and Interpolation for ToF Measurement

High-precision time-of-flight (ToF) measurement is the key to flow rate measurement of ultrasonic gas flowmeters. At present, the measurement accuracy of cross-correlation method, which is one of ToF measurement methods, depends on the high-speed ADCs. However, these high-speed ADCs, which have high cost, cannot be applied to low-power embedded systems and meet the practical requirement for actual industrial applications. To improve the accuracy and resolution of difference of ToF(dToF) measurement under the premise of satisfying the low-power, this paper proposes a novel signal processing method based on cross-correlation and interpolation. The echo signal is sampled by ADC in low-power embedded system, and the cross-correlation calculation is performed after digital filtering. Cubic spline interpolation is applied to improve the accuracy and resolution. The effectiveness of the proposed cross-correlation combined with interpolation method was verified and discussed. Experiment results show that this proposed method can significantly improve the resolution of dToF and the accuracy of ultrasonic gas flow rate measurement. This method provides a new tool and illuminates a good potential for real-time and high-precision flow rate measurement in low-power embedded systems.