| 摘要 |
PROBLEM TO BE SOLVED: To extend the life of a potentiometer (a variable resistance).SOLUTION: Venturi valves 103A, 103B acting as local discharging valves from a fume hood 101 are installed and an air quantity control device 107 is installed with respect to the venturi valves 103A, 103B. The air quantity control device 107 changes set air quantities Q, Qfor the venturi valves 103A, 103B by adjusting a discharging air quantity Qcalculated in response to a position of a sash 105 while changing its adjustment rates α1,α2 at a prescribed interval T until the position of the sash 105 is changed next time after the position of the sash 105 is changed. This avoids a situation in which the target shaft positions for the venturi valves 103A, 103B change while the sash 105 remains at the same position and wearing of a potentiometer (a variable resistance) for detecting the shaft position proceeds at a specific position. |
