It is applicable to the measurement of gas flow in closed pipelines and can be widely applied to the flow rate of non-corrosive gases such as natural gas coal gas inert gas and air. It is an ideal flow metering device for petroleum chemical industrial civil boilers gas pressure regulating boxes scientific research and other departments. As a traditional positive displacement instrument it uses a rotary fixed displacement principle with precision from a pair of precision machined rotors and a robust metering chamber to ensure permanent and high accuracy.