Smart Filament Emission Controller For Supersonic Gas Chromatography-Mass Spectrometry Using Real Time Digital Signal Processor

摘要

In electron ionization source, electrons are produced through thermionic emission by heating a wire filament, accelerating the electrons by high voltage and ionizing the analyzed molecules. In such a system, one important parameter is the filament emission current that determines the ionization rate, therefore, one needs to regulate this current. On the one hand, fast responses control is needed to keep the emission current constant, but on the other hand, we need to protect the filament from damage that occurs by large filaments current transients and over heating. To control our filament current and emission current, we developed a digital circuit based on a DSP controller that has several modes of operation. We used a smart algorithm that has a fast response to a small signal and a slow response to a large signal. In addition, we have several protective measures that prevent the current from reaching unsafe values.