On the problem of developing of the ultrasonic fixed liquid level sensors

Abstract

A new method of the liquid level sensing in pipe-line is described. The Lamb waves with slow increasing frequency were excited in the pipe wall. The covering curve of the Lamb waves as a time function was stored and FFT carried out. There are several harmonic frequency lines in spectrum of the empty pipe. Some of the lines disappear in pipe filled with liquid. It may be explained as the influence of the radial longitudinal waves resonance in liquid and increasing attenuation of the Lamb waves in wall. The ratio of the harmonic and unharmonic parts of the spectrum shows a great decreasing, when the liquid level coincides with the point of transmitting/receiving of the Lamb waves and may be used as an output signal. References 6. Figures 3.