Measuring the Level of Liquid in a Partially-Filled Pipe Via the Ultrasonic Pulse-Echo Method Using Acoustic Modeling

A method for measuring the level of liquid in horizontally oriented pipes was designed, developed and tested. A circuit custom-built for this purpose was used to generate modulated ultrasonic pulses that were applied to a piezo-electric transducer that was used both to launch the acoustic signal and record the returned echoes. The return signal was digitized and transmitted wirelessly to a remote computer for processing where the fluid level measurement consisted of comparing the acquired signal with a simulated signal based upon a model of acoustic wave propagation through the media comprising the set up using cross-correlation with the liquid depth as the free parameter. Laboratory experiments performed with this technique on a steel pipe have shown that it is capable of measuring fluid levels with errors less than 5 mm. Tests on other pipes have been performed, although results were not as accurate. A field test on a pipe in a water tunnel facility successfully determined the presence and absence of liquid in a noisy environment.