THERMIONIC EMISSION CURRENT CONTROL CIRCIT FOR GAUGE HEAD OF QUADRUPOLE MASS SPECTROMETER OR HOT CATHODE IONIZATION GAGE

摘要

PROBLEM TO BE SOLVED: To prevent a filament from being discontinued by not carrying an excess inrush current when inputting a power source. SOLUTION: When a switch 12 is turned on, a variable current source 10 raises a filament current in accordance with the potential rise of a junction point 50 of a CR time constant circuit 32. When a filament current limiter 30 detects a 0.3A, the filament current is controlled to maintain the value for four seconds (the time constant of CR time constant circuit 32) for preheating a filament electrode 102. After four seconds, switches 24 and 48 are switched to the N-side, the variable current source 10 is controlled based on the magnitude of a thermoinic emission current, the filament current rises and reaches 1.8A corresponding to a desired thermoinic emission current of 0.5 mA to maintain the stationary state thereafter.