| 摘要 |
PROBLEM TO BE SOLVED: To properly control a flow rate so as to provide a calibration gas at a desired concentration even if supply of a constituent gas is in a low flow rate area. SOLUTION: A mass-flow meter 4 is arranged in a supply system of the constituent gas, and according to a signal equivalent to a measurement error by this mass-flow meter 4, measurement sensitiveness of a mass flow controller 2 for the gas constituent is corrected. Therefore, even if the constituent gas flow rate is low, a flow rate error is less and a calibration gas of a desired concentration can be obtained.
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