With the continuous development of science and technology, ultrasonic flowmeter applications gradually wide, and are ideal for flow measurement. With multi-beam and digital signal processing technology, the ultrasonic measuring instrument can achieve high measurement accuracy. Unlike conventional turbo meters,  it has no moving parts and therefore requires little or no maintenance. Moreover, it does not block or slow down the flow of gas or liquid in the pipeline.

According to different measurement principles,  ultrasonic flowmeter can be divided into the propagation time difference method, Doppler method,  which is based on Doppler Doppler effect in the sound waves, the detection rate for the drift frequency.  The use of Doppler method of harsh conditions, only suitable for measuring a liquid containing a certain phase.  At present, propagation time difference method is widely used for flow measurement. The velocity of the gas is independent of the speed of sound, only depends on the sound path length of the ultrasonic wave,  the angle between the fluid flow direction and the propagation direction of the ultrasonic wave and the time of the ultrasonic wave propagation in the gas. Ultrasonic flowmeter has a high measurement accuracy.

Ultrasonic flowmeters (hereinafter referred to as USF) are instruments for measuring volumetric flow by detecting the action of an ultrasonic beam (or ultrasonic pulse) on a fluid flow.  This paper focuses on the USF for measuring the liquid flow rate of closed conduits.  70 years with the 20th century,  the development of electronic technology, improving the performance of various models of USF into the market.  It was predicted that the USF measurement principle is the length and time of the combination of two basic quantities, the derived traceability is better,  it is possible to establish a flow benchmark.

Ultrasonic flowmeter is through the ultrasonic flow in the flow of fluid, bearing fluid flow rate information,  the signal processing,  converted into traffic information. Ultrasonic flowmeter compared with the traditional flowmeter, with a small size, measuring range,  easy installation, maintenance-free, zero pressure loss and low initial flow rate, etc.  is an ideal flow juice.  It is capable of accurately measuring the broadband of liquefied petroleum gas (LPG) products without having to be verified as mechanically.  High sensitivity makes it possible to detect any leaks in the pipeline, and can measure and supplement variables that affect measurement accuracy in the field of custody transport.