Method and apparatus for measuring gas flow

A gas flow measuring apparatus for measuring a gas flow, comprising:

• a first flow path connected to a flow controller;
• a third flow path connected to the first flow path by way of a second flow path;
• a valve disposed between the second flow path and the third flow path;
• a pressure sensor configured to measure a pressure of a gas filled in the third flow path;
• a temperature sensor configured to measure a temperature of the gas;
• and
• a controller,
• wherein the controller is configured to control the gas flow measuring apparatus to perform processes including:
• measuring a first pressure of a gas filled in a first flow path connected to a flow controller and a third flow path connected to the first flow path by way of the second flow path;
• supplying, after the first pressure is measured, a gas to the first flow path and the third flow path, by way of the second flow path, in a state where the valve is opened by repeating multiple times (i) gas supply to the first flow path through the flow controller, and (ii) stop of the gas supply to the first path through the flow controller, after a predetermined time from a start of the gas supply to the first flow path through the flow controller, and by diffusing the gas supplied to the first flow path to the third flow path by way of the second flow path;
• measuring a gas supply time from a signal for starting the gas supply to the first flow path to a signal for stopping the gas supply to the first flow path, the signals being outputted from a controller to the flow controller when the gas is supplied to the first flow path and the third flow path by way of the second flow path;
• measuring a second pressure and a temperature of the gas filled in the first flow path and the third flow path after the gas is supplied to the first flow path and the third flow path by way of the second flow path using the pressure sensor and the temperature sensor;
• measuring a third pressure and a temperature of the gas filled in the third flow path using the pressure sensor after the gas is exhausted from the third flow path in a state the valve is closed and the first flow path and the third flow path are not connected to each other;
• measuring, after the third pressure is measured, a fourth pressure of the gas filled in the first flow path and the third flow path using the pressure sensor in a state where the valve is opened and the first flow path and the third flow path are connected to each other by way of the second flow path;
• calculating a gas flow of the gas supplied to the first flow path and the third flow path by way of the second flow path through the flow controller based on the first pressure, the second pressure, the third pressure, the fourth pressure, and the temperature;
• calculating an average time of the gas supply time measured by repeating the gas supply and the stop of the gas supply multiple times;
• and
• correcting the calculated gas flow based on a theoretical gas supply time in the controller and the calculated average time.