Research On Ultrasonic Gas Flowmeters Based On Pseudo Random Code Correlation

Ultrasonic flowmeter is applied widely in industrial measureing filed, because of its advantages of noncontact installation and maintenance with ease. In the filed of natural gas measuring, ultrasonic flowmeter has evident potential and advantages, such as without mobile component, without pressure loss and high precision in measurement. With relevant standards promulgated and practicality explored, ultrasonic flowmeter must be developed at this filed in the future.Pseudo Random code is introduced to the correlation time-difference method of ultrasonic flowmeter. Correlation time-difference method combines traditional time-difference method with the correlation method, and inherits their merits. To ensure the sharp figure, the pseudo random code, due to their variety and simplicity, served as the modulation signals in the proposed method. The simulations were carried out to configure the coded waveform parameters including sequence length, code width and code amplitude.The experimental part of this investigation details how to encode the ultrasonic waveform. Hardware system is composed of the emission, reception and procession of the ultrasonic signal. The emission part is designed of random waveform generator, which can generate Pseudo Random code directly. The reception and procession part is responsible to demodulate Pseudo Random signal from the ultrasonic signal after amplified and filtered, and restricted in the anticipant range.Using the digital random wave generator, carry through the coding characteristic experiment on the SensComp ultrasonic transceiver piezoelectric transducer. By means of sampling the coded ultrasonic signals and correlating them through mathematic software, compared the results of different coded manners, such as Barker-sequences, m-sequences, and L-sequence. The system finally got verified on the gas flow facility at the Process Detect and Control laboratory in Tianjin University.