The commonly used unit in engineering is m3/h, which can be divided into instantaneous flow rate (Flow Rate) and cumulative flow rate (Total Flow). Instantaneous flow rate refers to the amount of effective cross-section that passes through a closed pipeline or open channel per unit time, and the substances flowing through can be gas, liquid, or solid; Accumulated flow refers to the cumulative amount of fluid flowing through the effective cross-section of a closed pipeline or open channel during a certain time interval (one day, one week, one month, one year). The cumulative flow can also be obtained by integrating the instantaneous flow rate with time, so the instantaneous flow meter and the cumulative flow meter can also be converted into each other.