A new type ionization vacuum gauge circuit by semi-conductor elements is described here. The advantage of this circuit over a conventional one may be summarized as follows;
(1) The lighter and smaller physical size is obtained.
(2) The value of pressure is indicated digitally by the indicating tube drived by an automatic range selector.
(3) A series regulating transistor operated by the feedback controlling pulse is used to keep the emission current of the ionization vacuum tube constant ; and thus the regulating transistor of a small power type is useful enough to be used, because of the pulsed filament current.
(4) MOS-FETs enable the more senstive detection of ion current up to the degree of a few nanoamps, which is useful to obtain a larger range of pressure lindication.
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