It is possible to respecify the product (
mass flow controller) corresponding to multiple types of actual process gases and multiple flow rate ranges, even after the
mass flow controller has been shipped. With the
mass flow
rate control device in an initial state,
calibration gas characteristic data is derived by measuring actual flow rate versus a flow rate setting
signal using a
calibration gas, and this
calibration gas characteristic data is then saved to
control unit. Meanwhile, actual gas characteristic data is derived by measuring actual flow rate versus a flow rate setting
signal for each of a plurality of types of actual gas, and this actual gas characteristic data is then saved to a storage medium. Subsequently, prior to operating the mass flow
rate control device, the actual gas characteristic data for an actual process gas is read from the storage medium via a computer, and the calibration gas characteristic data that was saved to the
control unit is read out. The calibration gas characteristic data is then converted to controlled flow rate correction data based on the actual gas characteristic data, and the controlled flow rate correction data is saved to the
control unit. Actual gas flow rate is corrected based on this controlled flow rate correction data.