If your number .... 100 mL .... or 100 cubic centimeters .... per actuation ...is correct, then the ultrasonic T/R might not be the best choice. A graduated cylinder, or anything of such a small dimension might have peripheral interference from the container walls ....The idea is to detect a distinct echo pulse from the fluid surface .......
A larger diameter cross sectional area would be better....have more of a chance of working properly. ...Apparently there is a dispersion of the ultrasonic wave from the transmitter ..... at some acute angle.
If you were to place a transmitter at some point above a 1 cm diameter cylinder, not within it, and generate a pulse, it may be that there would not be sufficient energy in the reflected wave to be picked up by the ultrasonic receiver.
A larger diameter cross sectional area would be better....have more of a chance of working properly. ...Apparently there is a dispersion of the ultrasonic wave from the transmitter ..... at some acute angle.
If you were to place a transmitter at some point above a 1 cm diameter cylinder, not within it, and generate a pulse, it may be that there would not be sufficient energy in the reflected wave to be picked up by the ultrasonic receiver.