Study And Implementation Of Signal Processing Method Based On Time Domain For GWRLG

Guided wave radar level gauge (GWRLG) is widely used to measure level in industrial production. For low measurement precision of the domestic signal processing methods commonly adopted, a novel signal processing method is proposed to deal with echo profile, and signal processing system is developed to realize real-time measurement.For gross error caused by wrong identification of surface echo, first-order derivative is performed, and multiple feature parameters are computed, and assembled in different ways to constitute judgment conditions for the surface echo. The reference curve is then combined to remove spurious echoes and obtain the surface echo, which improves the accuracy and reliability of identification of surface echo, and reduces gross error.For too many calibration points and low measurement precision problem, pre-processing is preformed to eliminate disturbances of noises. The point with the minimum slope is selected on the surface echo as the positioning point for timing, and linear interpolation is performed to determine start so as to achieve good linearity. A second order Lagrange interpolation is performed on the positioning point, a median average filtering is performed on multiple calculation results and 3-point 3-segments calibration are imposed to reduce non-linear error.Based on the hardware platform provided by a domestic company, a signal processing system with low power consumption MCU MSP430F5418A as the core is developed, realizing the real-time measurement. To verify the effectiveness of method proposed, repeated experiments were conducted on different medium under different environment. In the case that theoretical error is 2.682-4.023 cm depending on the hardware platform, based on 3-point calibration, the blind area for water is 15 cm, the precision is less than 1cm, the repeatability is 4 mm, and strong disturbances can be overcome. For media of small dielectric permittivity like oil, the precision is less than 2.5 cm. For long distance measurement up to 8 m, the precision is less than 0.7%. The experiments results show that, method proposed has improved the measurement accuracy, and real-time measurement for different medium under different conditions can be realized.