Research Into Ultrasonic Flowmeter For Wind-speed In Air-conditioning Ducts Based On FPGA

Accurate measurement of wind speed parameters in air conditioning andventilation ducts, is the foundation of large-scale air-conditioning and ventilationequipment control system. This paper takes precise ultrasonic velocity measurementin air-conditioning ducts using way as the main goal. Based on the comprehensiveanalysis of principle, the main advantages and disadvantages in various pipe velocitymeasurement, research into the time-difference ultrasonic velocity measurementsystem, using a FPGA chip as the core unit, of air conditioning ducts. Provide a newapproach for the development of practical new air conditioning ducts anemometer,which promote the development and application of measurement and controltechnology, has important academic value and practical significance. The main workincludes:⑴Analysis and comparison the characteristics of Pitot tube, hotline mass flowmeasurement which based on the principle of thermal heat exchange membrane andthe ultrasonic flowmeters etc. Analysis the details of the ultrasonic velocity measure-ment method in pipeline, proposed a FPGA-based time-difference ultrasonic velocitymeasurement system design in wind speed measurement, verified the accuracyrequirements of all the functional component of the measure-system.⑵According to the design requirements of each functional module, accomplishultrasonic transmitter driver circuit, processing circuit for received signal, tem-perature measurement circuit and other system peripheral circuit design. Against thephenomenon that the received signal is affected by interference from higherharmonics when using square wave as ultrasonic probe drive signal. Proposed to use ahigh pressure single cycle sinusoidal signal driving the ultrasonic probe ultrasonicsignal transmitting, and from the perspective of system security, a low voltage powersupply design uses ultrasonic transmitter driver scheme is developed.⑶Based on control tasks of the master chip(FPGA) and system measurementprocesses, A module partition for logic control is applied on the FPGA chip, andsystem operation control timing is given. Combining ultrasonic receiving signalactual and FPGA chip features, proposed a method to determine the arrival time ofultrasonic signal, developed a FPGA-based high-precision phase discriminator andtiming modules design, achieved ultrasonic propagation time acquisition and precision measurements.⑷By changing the channel length of the ultrasonic wave propagation, carried outan ultrasonic propagation time measurement experiment to verify the high-precisiontime measurement function.