An ultrasonic sensor detects a liquid level. A substrate (707) has an acoustic array (705). An acoustic diversion array (710) can be between a substrate edge (713) and the acoustic array. A sensing region (701) can lay next to the acoustic array opposite the acoustic diversion array. A collimation groove (706) can be in the substrate along a length of the acoustic array next to the liquid level sensing region. Multiple longitudinal folds (801, 802, 803) can run parallel to and between acoustic source and receive arrays. A feed strip (1201, 1202, 1309, 1311) can be used with a bend (1203, 1204) acoustically coupled to the acoustic array and an ultrasonic transducer at another end of the feed strip. The feed strip runs along the entire acoustic array when top fed and runs along part of the acoustic array when fed through a side of a tank (1401).