| 摘要 |
PURPOSE:To check quickly and accurately a flow by providing a gas flow controller, a flow designating means, a difference calculating means calculating the difference of flow between the gas flow controller and a flow setting means, a check value setting means and a comparator means so as to attain supervision always and checking with a prescribed condition at all times even if the flow changes. CONSTITUTION:The flow is designated to a mass flow controller 1 by a potentiometer 14. The flow output of the mass flow controller 1 is inputted to an operational amplifier 16 via resistor 12 and the designated flow is given to the amplifier 16 via resistor 13, and the difference of flow is calculated. Potentiometer, 17a, 17b set respectively a positive and a negative limit of the flow difference, comparators 18a, 18b compare respectively the limits with a flow difference output 20, the result is ORed by an OR circuit 21, and when either output exceeds the limit, an output 19 is logical '1' and an error signal is outputted. Since terminals 22a, 22b of the potentiometers 17a, 17b are connected to the output of the potentiometer 14, the check condition is set by the percentage of the designated flow. |
