The Design Of Helium Ionization Detector

The gas chromatograph (GC) is a kind of fast and efficient analytical instruments. The device has been widely used in life science, chemistry, material science, and environmental sciences. The detector is an important component of the gas chromatograph. Compared with other detectors, the helium ionization (HID) detector is the only intrinsically safe, nondestructive universal detector, is one of the highest sensitivity detector and can produce response to all volatile substance from permanent gas to complex organic molecules without the neon. However, the HID is rarely developed and applied in China. With the rapid development of our semiconductor industry and economy, the application prospect of the HID is broad.The HID has been studied in this paper.The principle of ionized helium is firstly summarized in this paper. Then, the pulse generator controlled is design to improve the Royer converter circuit. And we test the performance of the generator circuit. Based on the pulse generator, we theoretically design the ionization chamber. We design the amplifier circuit with AD549. The amplifier circuit can take 100pA signal amplifier 108 times or 109 times. And we make many tests to the amplifier circuit. We design the A/D circuit (Airborne Digital Computer(ADC)) with AD7799. The analog signal outputed by the amplifier circuit is transformed into the digital signal with the ADC. We design the main control circuit with the LM3S8962 microcontroller. The main control circuit can control circuit of Ethernet and the A/D circuit and realize digital signal processing. The data processed by the main control circuitis is transmitted to the chromatography workstation via Ethernet. We can observe the signal waveform by the chromatography workstation.With the physical environment of the GC9800 manufactured by Shanghai Kechuang, We test the liquor and the nitrogen containing methane with our design. We compared the signal waveform outputed and the standard waveform. Compared with the standard waveform, there are many little interference on the signal waveform. But the prototype components could been completely analyzed with the signal waveform. This means that we have achieved the goal to study the HID.