| 摘要 |
PURPOSE:To prevent an unstable control action like hunting, etc. by using the value obtained by giving addition/subtraction of the variable value set previously to the detected value of the same control loop system to give a command to one of a rotational frequency controller and a stroke controller having different control characteristics. CONSTITUTION:An injecting amount controller supplies both outputs of a rotational frequency detector 1 and a stroke detector 2 to a controller 5 of a 1-loop controller 14 in the form of a process variable PV through a multiplier 3 and then actuates a rotational frequency controller 6 and a stroke controller 7 with the operating output corresponding to the deviation compared with the set value SVa of flow rate given from a ratio setting unit 4. Here alarm setting units 8 and 9 which are turned on when the operating output of the controller 5 gets out of the set value are added together with analog switches 12 and 13, an adder 10 and a subtractor 11. Then the level of the operating output value is discriminated 8 and 9. If the output value exceeds the set value, the switch 12 is turned on with the switch 13 turned off respectively. Thus the signals underwent addition and subtraction are delivered via an adder 10 and a subtractor 11 which are optionally selected.
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