A flow rate assembly can include a housing having a measurement channel extending along the housing axis and through a portion of the housing between the first and second ends of the housing, an outer cup portion positioned at least partly within the housing, and a transducer positioned within the outer cup portion and sealed from fluid flow past the outer cup portion, the transducer having a width perpendicular to the housing axis and greater than the width of the measurement channel, the transducer configured to generate an ultrasonic signal and to direct the ultrasonic signal through the measurement channel.