Ultrasonic Phase Detection Method Of Ultra Low Frequency Vibration Sensor And Its Realization By FPGA

Ultra low frequency vibration is a common physical phenomenon, the vibration of mine derrick, well tower, high-rise buildings, railway highway bridges, dams are such phenomen. This kind of vibration has a very low frequency, 1Hz frequency component is very rich and it might have a large amplitude, and the characteristics of strong destructive power. In the field of engineering technology, test and Research on the ultra low frequency vibration has been the subject of attention. This paper designed a kind of ultra low frequency vibration sensor with FPGA that can achieve ultra-low frequency vibration measurement, the work has great significance.In this paper, the design of ultra low frequency seismic geophone is based on ultrasonic phase method. The detector is composed of a casing, spring oscillator structure, and ultrasonic probe. The main principle is the vibration wave is coupled to the quality block resonance occurs. The target vibration information is derived by using the displacement variation law in the vibration process of the mass block. The mass displacement detection by ultrasonic transceiver sensor estimates the real-time phase difference is obtained.In order to fix the error on ultrasonic measurement results because of the temperature changing causing the ultrasonic wavelength change, this paper puts forward a method of differential measurement, ensuring the total ultrasonic wave processing remaining the same to obtain the real wavelength. In order to meet the full period sampling, this paper presents an ultrasonic signal based on FPGA sampling circuit and sampling signal of homologous ideas. Because the existence of vibration velocity, the ultrasonic receiving end waveform occurrence frequency offset, the traditional phase algorithm is difficult to apply, in order to solve this problem, this paper uses a phase algorithm based on adjacent signal subtraction. And the algorithm is verified by simulation method, the simulation results show that the algorithm itself calculation error does not affect measurement accuracy. Finally, it is concluded that the sensor frequency response curve through the experiment and validate the differential structure can effectively reduce the influence of temperature on the measurement results.