PID (photo-ionization detector)

Abstract

The invention provides a PID (photoionization detector). The PID comprises an ultraviolet lamp, an ionization chamber, an analyzed gas inlet pipe inserted into one side of the ionization chamber and an analyzed gas discharging pipe inserted into the other side of the ionization chamber, wherein the lower part of the ultraviolet lamp is inserted into the upper part of the ionization chamber, and analyzed gas enters the ionization chamber via the analyzed gas inlet pipe and ionized under irradiation of ultraviolet light, produces current for data acquisition under the action of an electric fieldin the ionization chamber and is discharged from the analyzed gas discharging pipe. A purge gas inlet pipe is inserted into the lower part of the ionization chamber, so that a gas outlet of the purgegas inlet pipe is located under a window of the ultraviolet lamp, the window of the ultraviolet lamp is uniformly and symmetrically purged and cleaned, and accordingly, the service life of the ultraviolet lamp can be effectively prolonged. Through reduction of the sizes and distances of electrodes in the ionization chamber, the volume of the ionization zone can be reduced, and the sensitivity ofthe detector is improved.

Description

technical field [0001] The invention relates to a photoionization detector for gas detection. Background technique [0002] Photoionization detector (Photo-ionization Detector, PID) is a kind of gas detector, which is widely used in gas chromatography analysis and organic volatile compound (VOC) detection. A photoionization detector consists of a UV lamp and an ionization chamber located below the UV lamp. The gas to be analyzed enters the ionization chamber through the inlet pipe, and the high-energy ultraviolet rays emitted by the ultraviolet lamp ionize the organic compounds or some inorganic substances in the gas to be analyzed. Under the action of the electric field, the ionized positive and negative ions are respectively captured by the collecting electrode and the bias electrode in the ionization chamber, and form a weak current, which is then amplified by the weak current and collected by the data acquisition card for subsequent data analysis. [0003] The long-ter...

AI Technical Summary

Problems solved by technology

Although the gas parallel to the window can clean the window to a certain extent, due to the uneven distribution of the purge air flow on the surface of the window, after a long period of use, along the direction of the air flow, the cleaning degree of different areas on the window will be different.

The window near the purge gas inlet pipe will be relatively clean, but other parts are still more polluted

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