A flow meter for measuring a flow rate of a fluid may include a cartridge containing certain components such as a flow sensor. The cartridge is removable from the flow meter such that it may be replaced with a new cartridge, allowing calibration of the flow meter while enabling the flow meter to continue to be operated with another cartridge in the place of the removed cartridge. The flow meter may be configured to direct fluid flow away from selected components of the flow meter.

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.

Apparatus for determining a measurement error of a displacement volumetric meter, the meter having bellows which in use expand and contract to transmit a fluid. The apparatus including a transducer operable to detect movement of the bellows and to generate a signal which varies in accordance with the movement of the bellows; and a computing device in communication with the transducer so as to receive the signal therefrom, the computing device being operable to determine a flow rate of fluid through the meter based on the signal, and to determine a measurement error of the meter based on the determined flow rate. A corresponding method, meter monitoring device and meter measurement error determining device are also disclosed.

Disclosed is a method of inspecting a flow rate measuring system used in a substrate processing system. The flow rate measuring system provides a gas flow path used for calculating a flow rate in a build-up method. A gas output by a flow rate controller of a gas supply unit of the substrate processing system may be supplied to the gas flow path. In the method, apart from a previously obtained initial value of a volume of the gas flow path, a volume of the gas flow path is obtained at the time of inspection of the flow rate measuring system. Then, the obtained volume is compared to the initial value.