Gas supply device capable of measuring flow rate, flowmeter, and flow rate measuring method

A flowmeter for measuring a flow rate of a flow controller, the flowmeter being attachable to and detachable from a gas supply system, the gas supply system comprising:

• the flow controller that controls a flow rate of a flowing gas;
• a first shutoff valve provided downstream of the flow controller;
• a second shutoff valve provided in a first flow passage communicating with a downstream side of the first shutoff valve;
• a branch flow passage that branches from the first flow passage between the first shutoff valve and the second shutoff valve;
• and a fourth shutoff valve provided in the branch flow passage,
• the flowmeter comprising:
• a fitting that is attachable to and detachable from the branch flow passage on a downstream side of the fourth shutoff valve;
• a third shutoff valve provided in a continuous flow passage connected to the fitting;
• a pressure sensing device for detecting an internal pressure of the continuous flow passage;
• a temperature sensing device for detecting an internal temperature of the continuous flow passage;
• a volume measuring tank connected downstream of the third shutoff valve and having a known volume;
• and
• an arithmetic and control unit,
• wherein the arithmetic and control unit obtains a passage volume by applying Boyle's law to open and closed states of the third shutoff valve, the passage volume being controlled by the first shutoff valve, the second shutoff valve, and the third shutoff valve with the fitting connected to the branch flow passage, and calculates a flow rate of the flow controller by using the passage volume and detection values obtained by the pressure sensing device and the temperature sensing device.

A flow measurement method for measuring a passage volume with a volume measuring tank and measuring a flow rate of a flow controller by an rate-of-rise (ROR) method using the passage volume, the passage volume being controlled by a first shutoff valve, a second shutoff valve, and a third shutoff valve, the first shutoff valve being connected downstream of the flow controller, the second shutoff valve being provided in a first flow passage communicating with a downstream side of the first shutoff valve, the third shutoff valve being provided in a flow passage that branches from the first flow passage between the first shutoff valve and the second shutoff valve, and the volume measuring tank being connected downstream of the third shutoff valve and having a known volume,

• the flow measurement method comprising:
• a first step of closing the first shutoff valve and opening the second shutoff valve and the third shutoff valve to exhaust a gas through the second shutoff valve;
• a second step of closing the second shutoff valve and the third shutoff valve;
• a third step of opening the first shutoff valve to pass a gas at a set flow rate through the flow controller, and then closing the first shutoff valve and detecting a first pressure in the first or second flow passage;
• a fourth step of opening the third shutoff valve and detecting a second pressure in a flow passage controlled by the first shutoff valve, the second shutoff valve, and the third shutoff valve;
• and
• a fifth step of calculating the passage volume controlled by the first shutoff valve, the second shutoff valve, and the third shutoff valve by Boyle's law using the first pressure, the second pressure, and the known volume for volume measurement.