Industry new

What are the factors affecting the accuracy of ultrasonic measurement?

All flow information obtained by the flow meter is obtained by ultrasonic signals. If the ultrasonic signal itself is problematic, both the propagation time measurement and the flow measurement will not be correct.
The signal processing method of the ultrasonic flowmeter can be divided into time domain and frequency domain analysis. In the method of time domain processing, the technical processing is to identify one or several predetermined zero levels in the received pulse, and when the received signal reaches a predetermined amplitude voltage, as a signal reaching flag, and start The zero-crossing detection unit then detects the first zero-level intersection after it as the signal channel time.
When the zero-crossing level is used to detect the ultrasonic propagation time, the signal waveform must be ideal because the detection point must be clearly defined within one pulse period.
In the measurement of gaseous media, the waveform of the ultrasonic signal is difficult to maintain stable. Gases typically require several sound pressures and pressure drops during transport, which can cause air pressure to change in the pipeline. Since the density of the medium varies greatly under different pressures, the acoustic energy of the actual emission and reception changes greatly due to the fluctuation of the pressure at different times of propagation, and finally the signal is distorted due to the fluctuation of the amplitude.
Particles or droplets in the gas also scatter and weaken the signal, and contaminants at the front of the transducer also weaken the signal. At high flow rates, shearing between different velocity layers can pull the signal apart, changing the gas component of the signal shape close to the critical condition, such as carbon dioxide, which can selectively attenuate certain frequency components in the ultrasonic signal, thereby changing the pulse. shape.

PREVIOUS：Instructions for using the five steps of the NEXT：Turbine flowmeter maintenance points introduc