The Study Of Pipeline Fluid Temperature Measurement Method Based On Ultrasound

The physical basis of ultrasonic temperature sensor is the characteristics of ultrasonic wave velocity changes with medium temperature's variety,realize the mathematical modeling of ultrasonic wave velocity and r medium temperature is the main idea of acoustic thermometer.The time difference method is one of the ultrasonic wave velocities measuring method,how to precise calculation the time of ultrasonic propagation in a medium is the important and difficult in the process of ultrasonic temperature measurement system design.The main research content is as follows:1.In the light of the high precision temperature measurement and quick response demand,using FPGA as the main control chip to the system hardware design,set the ultrasonic output signal driver circuit and high-speed signal acquisition system and realize ultrasonic signal transmission and acquisition of 2 MHz Through RS232 serial communication circuit,sampling data real-time transmission,folks could intuitive view the waveforms and temperature change trend in the upper machine written by LabVIEW program.2.Apply Verilog HDL hardware description language for software design,in view of the different peripheral module and signal processing requirements,from the top down design method will be the function of the system is divided into eight Behavioral level module.Mainly includes: clock management module based on the basis of DCM;combining the DDS and sine wave LUT,control ultrasonic excitation signal output;use a serial port communication of upper machine and lower machine data interaction,designed the command parsing function;use a lot of IP core optimization of the structure of the system,such as FI R digital filter and dual port RAM.In addition,I also designed the high-speed signal acquisition control and system workflow control state machine.3.On the basis of the calculation method of passing zero time difference method,set a precise delay before acquisition signa l.This method optimized the signal storage and data analysis.The design of real-time characteristic wave extraction and passing zero point search algorithm,caused the ultrasonic propagation time measurement precision in nanoseconds.4.After system simulation,debugging and verification,respectively,for a specific fluid static experiment and dynamic experiment was carried out.Then according to the ultrasonic propagation time experimental data analysis results,established the mathematical model of ultrasonic wave velocity and medium temperature.Repeatability and uncertainty analysis results note that the system has reached the design target.