Level Measurement using ultrasound
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This thesis describes the development and performance of a level measurement system based on estimating the round-trip-time of an ultrasonic signal. A new prototype is designed and constructed, built on the foundations of an ultrasonic speed of sound measurement system made by Wema System AS. Tests are performed and data is recorded under noisy conditions, such as vibrations created by a vibration bench at Wema HQ, and also simulated temperature changes, such as the presence of bubbles in the liquid. Different procedures for trigging the transducer is compared in terms of noise resistance and signal strength. Software is developed in Matlab as to detect ultrasonic echoes and estimate the Round-trip-time for the ultrasonic signal as to calculate a level-estimate. Properties related to the success of said software are explored, such as signal strength as a function of liquid level. A software model in k-wave is developed to simulate the ultrasonic signal propagating in an environment similar to that of the system. Finally, tests are conducted with the presence of a diesel layer on top of the DEF. A procedure for detecting a diesel layer on top is suggested, based on experimental data.