An ultrasonic sensing device includes an ultrasonic signal transmitting element and an ultrasonic signal receiving element. The ultrasonic signal transmitting element is configured to produce ultrasonic waves. The ultrasonic signal receiving element is configured to receive ultrasonic waves. The ultrasonic signal transmitting element and the ultrasonic signal receiving element are positioned at a same plane. A distance between the ultrasonic signal transmitting element and the ultrasonic signal receiving element is adjustable. The ultrasonic signal transmitting element is capable of emitting ultrasonic waves having a conical shape.
