If the diesel engine has a superior economic performance, a dependable work, and if the noise and the vibration can be controlled in a lower limit, which usually depends upon its valve train system.

The assemble criterion of sensor for design was advanced. At last, a method of increasing signal-to-noise ratio and reducing flux lower limit value of vortex flowmeter was advanced.

This is a time-domain signal processing method which has a lower signal to noise ratio limit. Therefore, it will have very good future in applications.