| 摘要 |
PURPOSE:To detect the abnormality of a fluid control means and a controller itself by monitoring the fluctuation state of operation for a prescribed period of time from the start of the control of a mass flow controller with a sequence controller and detecting the abnormality of the mass flow controller. CONSTITUTION:A sequence controller 1, in which a set value for a flowrate and the allowable range and monitoring time of the flowrate are set, monitors the fluctuation of a gas flowrate within the monitoring time set immediately after starting gas supply and detects the abnormality of gas flowrate. When a mass flow controller 2 is abnormal, a set flowrate range (set value + or -2%) is not reached within 15 seconds and the abnormality is detected by the sequence controller 1. The fluctuation which occurs at the early stage of the supply of gas is not judged as abnormality because it remains within 15 seconds the same as that in a normal case. That is, the abnormal operation caused by the abnormality of the fluid control means 18 detected but the abnormal operation caused the other factor is not detected. |
