GB777005A - Improvements relating to mass spectrometers - Google Patents

Abstract

777,005. Automatic voltage control systems. GENERAL ELECTRIC CO. June 8, 1955 [June 9, 1954], No. 16485/55. Class 38 (4). [Also in Group XL (a)] The amplitude of the R.F. voltage applied to a mass spectrometer in which resonant ions of different mass are measured as the frequency is varied (see Group XL (a)) is automatically adjusted to the correct value at each frequency for optimum resolving power and sensitivity. The applied R.F. voltage is rectified at 22 and compared in differential amplifier 21 with a reference voltage derived from potentiometer 16, and an error signal is fed to grid 122 of the cathode follower 23 between oscillator 11 and spectrometer 10. The tapping 16a of potentiometer 16 is varied simultaneously with the oscillator tuner 12. In another embodiment the frequency is adjusted successively to preselected values by inserting preset condensers simultaneously. The correct preset resistors are inserted for determining the magnitude of the input to the spectrometer. Preset resistors between an amplifier which follows the spectrometer and a recorder may also be inserted for optimum recording sensitivity. An additional variable condenser may be permanently inserted in the oscillator circuit and operated to sweep the oscillator in the neighbourhood of each selected frequency. An automatic amplitude control circuit may also be used in this embodiment. The oscillator may be tuned by inductances instead of condensers.