According to the application examples up to now, it can be seen that most fluid media can be detected by ultrasonic flowmeter. The application scope extends from the original sewage measurement to the measurement of natural gas, air, methane, nitrogen, ammonia, gasoline, air, phosphoric acid and heavy oil; It can even measure nitrogen, purified water and oil-water mixture. In addition, in petrochemical refineries. The combustion optimization of residual gas needs to measure the flow rate by ultrasonic time difference method, and determine the molecular weight of the measured gas by ultrasonic propagation velocity and other measurement results.

However, ultrasound cannot pass through vacuum. The precondition of ultrasonic propagation between sensors is that the measured gas should have at least the specified minimum density. Moreover, when using ultrasonic flowmeter to measure liquid flow, the content of gas and solid in liquid cannot exceed a certain limit, which is mainly due to excessive damping effect (reflection caused by ultrasonic encountering interfering substances). Ultrasonic sensors cannot be applied as follows:

The volume content of bubbles in the liquid is more than 1%;

The volume content of solid particles in the liquid is greater than 5%;

Liquid with viscosity greater than 100X10-4kg/ m pipe diameter.

Like a tuning fork of an organ or harmonica, a blocked part in a pipe (such as a valve spool) can generate a high-frequency sound level signal with a frequency range above 1OOkHz. In order to reduce the influence of blockage components on ultrasonic measurement, the straight-through pipeline must be guided by a non-interference inlet, but due to the friction between gas and pipe wall, gas flow loss will also occur in this pipeline.