A gas sampling mechanism protecting an odor sensor and permeable membrane against direct exposure to the gas molecules of an external environment provides a one-way airflow, and includes an inlet chamber, a pump chamber connected to the inlet chamber, and a pump assembly connected to the pump chamber. The pump chamber can compress or evacuate air inside the pump chamber. An inlet valve is moveably arranged between the inlet chamber and the pump, and an outlet valve is movably arranged between the pump chamber and the ambient.

Provided is a wide-range diaphragm gas meter, comprising a machine core. The machine core comprises a diaphragm chamber, two diaphragms, two diaphragm covers, a valve cover, and a four-axis rotational system. The diaphragm chamber comprises a valve seat and two measuring chambers, and the two diaphragms are located in the two measuring chambers respectively. Each of the diaphragms is connected correspondingly to the four-axis rotational system. A vertical shaft is fixedly connected to one end of a rotating bar, the other end of the rotating bar is hinged to one end of a connecting bar, and the other end of the connecting bar is hinged to a crank. The central shaft of the crank is a third rotating shaft. A central crankwheel is arranged on a central shaft. The valve cover and the central crankwheel are coaxially arranged.