Patent ID: 8744784

Claim:
A diagnostic mechanism in a differential pressure type mass flow controller, the diagnostic mechanism comprising: a control unit configured with instructions executable by the control unit to: output from a valve control signal output section a signal for making a valve arranged in a flow channel wherein a fluid flows in a closed state; receive at a signal receiving section an inlet side detection signal and an outlet side detection signal from pressure sensors arranged at an inlet side and an outlet side of a differential pressure generating resistive element respectively, the differential pressure generating resistive element arranged in the flow channel; calculate at a diagnostic parameter calculating section a diagnostic parameter for diagnosing an abnormality in the differential pressure type mass flow controller, wherein the diagnostic parameter has a value based on a time-integrated value of a mass flow rate that is calculated based on a pressure at one of the inlet side or the outlet side obtained from one of the inlet side detection signal or the outlet side detection signal, respectively, during an interval while the pressure at one of the inlet side or the outlet side changes from a predetermined first pressure to a predetermined second pressure in a state where the valve is closed; and compare at a comparing section the value of the diagnostic parameter with a previously determined specified value.