Gain control for a quadrupole mass spectrometer

In a quadrupole mass spectrometer wherein a gaseous mixture is sequentially scanned to obtain a measurement of the relative abundance of each component thereof, control means for automatically compensating for variations in ionization, gas transportation and detection efficiencies of said gaseous mixture to continually obtain an accurate analyzation, said control means comprising:

• first amplifier means for generating an ion detection signal representative of each component in said gaseous mixture as established through the scanning of the gaseous mixture;
• demultiplex means for converting said ion detection signal for each component into a corresponding output signal in synchronization with the sequential scan of the gaseous mixture;
• channel means for communicating said output signal to an indicator means to inform an operator of said relationship of each component in said gaseous mixture;
• adjustment means associated with said channel means for modifying the output signal of a known gas sample presented to an ionizer to calibrate said indicator means;
• first resistor means connected to said channel means for reducing each of said output signals to produce a proportional output signal corresponding to the concentration of each gas in the gaseous mixture;
• junction means connected to said first resistor means for combining said proportional output signal of each of said components to produce a component signal;
• second amplifier means connected to said junction means for increasing the amplitude of said component signal;
• second resistor means associated with said second amplifier means for controlling the gain of the component signal;
• comparator means connected to said second amplifier means for comparing said component signal with a reference signal to establish an error signal;
• and
• integrator means having a ramp amplifier and a capacitor means responsive to said error signal for establishing a gain signal for proportionally modifying each of said ion detection signals from said first amplifier means in a manner such that the component signal is brought into equalization with said reference signal in a series of uniform steps.