| 摘要 |
PURPOSE:To previously take a preventive step, by generating an alarm signal before an optional time for the filament to be broken in an electron gun. CONSTITUTION:An electric current flowing in a filament 1 is measured by a current measuring circuit 8 and output to a recorder 10 to allow the recorder 10 to record a calibration curve of time aging for an output voltage proportional to the current value till the filament 1 is disconnected. A comparator circuit 9 compares an output of the current measuring circuit 8 with that of a reference voltage generating circuit 11, and the display element of a display circuit 12 is turned on when the output voltage of the current measuring circuit 8 comes to be at most the output voltage of the reference voltage generating circuit 11. |
