RBH100 series open channel ultrasonic flow meters are designed for continuously monitoring the flow rate and total flow in open channel. It is suitable to measure flow under open channel condition of water conservancy, hydropower, environmental protection and other industrial and agricultural environment. The meter is built in EEPROM module, ensure that total flow will not be lost when power failure. Ultrasonic Open Channel Flow meters use ultrasonic principle to test the liquid height. In accordance with the condition of free flow in the specific weir, with the function of liquid height and flow rate, the micro-computer can work out the corresponding flow. Instruments are also equipped with explosion-proof and anti-corrosion type probe specifically designed for petroleum and chemical department; it can meet explosion-proof area sewage flow measurement requirements of petroleum and chemical department, especially suitable for oil wastewater of flow measurement. explosion-proof class is Ex ia（d）iaⅡBT4.