Abstract: An aroma diffuser includes a liquid storage means, an enclosure provided with a mounting cavity, a gas supply means and a seal. The enclosure is covered on a liquid storage mean. The gas supply means and the liquid storage means are both aranged in the mounting cavity and communicate with each other. The gas supply means, the liquid storage means and the enclosure cooperate to form a gas return passage. The seal is arranged between the liquid storage means and the gas supply means, located in the gas return passage and sealingly abuts on the enclosure. The gas return passage can be blocked by the seal, aroma gas produced by the aroma diffuser is prevented from flowing back from the gas return passage into the gas supply means to reduce the concentration of the aroma gas released into the environment and thus to affect the use effect of the aroma diffuser.

Abstract: An ultrasonic measurement system and a measurement method thereof are disclosed.