| 摘要 |
PURPOSE:To prevent the overheat of a filament and thereby to improve the reliability of an apparatus by monitoring constantly the flow rate of a sampling gas in a nuclear reactor or the like, and by controlling a current to the filament of an ionization detector in accordance with the flow rate. CONSTITUTION:A differential-pressure detector 7 which collects sodium particles in a gas by filters and determines the concentration of the particles from a change in a differential pressure before and behind the filters is provided, and a signal 12 of the differential pressure between the filters is given to a comaprator 13 to be compared with a reference voltage signal 14. Moreover, a magnet switch 17 is incorporated in a circuit 18 supplying a current to a transformer 22 which feeds a filament 8 of a sodium ionization detector, and an operation of feeding from a power source 16 is controlled to be made and broken through the intermediary of the switch 17. A power supply to the filament 8 of the sodium ionization detector is interrupted by the switch 17 when the differential- pressure signal 12 falls below a reference voltage, the circuit 18 is thereby opened, and thus the power supply to the transformer 22 is discontinued. |
