Mass flow controller

A mass flow controller, comprising:

• a flow sensor which outputs a flow rate signal corresponding to a flow rate of a fluid,
• a flow control valve which controls the flow rate of said fluid by adjusting an opening degree of the valve,
• a flow rate setting means to which a flow rate setting value of said fluid is input, and
• a control means which outputs a valve opening degree signal to said flow control valve, and
• said mass flow controller performs flow rate control at an action position where said fluid acts at different flow rates depending on supply periods,
• wherein said control means is configured so as to:
• in a first period from a first time point that is a time point when a first setting value that is a flow rate setting value other than zero is input to said flow rate setting means to a second time point that is a time point when it is judged that said fluid has reached said action position, output said valve opening degree signal to said flow rate control valve such that a flow rate measured value determined based on said flow rate signal is larger than said first setting value,
• in a second period from said second time point to a third time point that is a time point when a second setting value that is a flow rate setting value smaller than said the first setting value is input to said flow rate setting means, output said valve opening degree signal to said flow rate control valve such that said flow rate measured value coincides with said first setting value,
• in a third period from said third time point to a time point when said first setting value is next input, output said valve opening degree signal to said flow control valve such that said flow rate measured value coincides with said second setting value, and
• repeatedly execute a control cycle consisting of said first period, said second period and said third period one or more times.