Ultrasonic fill level device and method

A fluid level monitoring system includes an ultrasonic interrogation device acoustically coupled to a sidewall of container and produces ultrasound that travels through the liquid along a transverse path and an inclined path . The liquid level is determined by calculating the times-of-flight for the received return signals, where the return signal along the inclined path reflects from the intersection of the liquid level and a sidewall . The device can be a multi-element transducer having a plurality of transducer elements at different angular orientations in a common housing.