FREQUENCY-PROGRAMMED ELECTRON-CAPTURE DETECTOR

摘要

Improved circuitry for increasing the sensitivity of an electron-capture ionization detector includes a closed-loop feedback circuit which varies the frequency of pulses which are applied to the detector. The circuit responds to greater concentrations of predetermined compounds such as gases by increasing the pulse repetition frequency and responds to lower concentrations by decreasing the pulse repetition frequency, always tending to keep the current flowing in the detector circuit near a constant preset value. The pulse frequency will then vary directly with the concentration of sampled compound in the detector, and simple frequency-to-voltage conversion devices can be used to signal such concentrations.