New operation principle for ultra-stable photo-ionization detectors

Authors: Liess M.1; Leonhardt M.

Source: Measurement Science and Technology, Volume 14, Number 4, 2003 , pp. 427-432(6)

Publisher: Institute of Physics Publishing

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Abstract:

Photo-ionization detectors (PIDs) are suited ideally to be combined with gas chromatographs (GCs). Without a GC, a PID can be used as a cheap unspecific sensor for noxious substances in the air. In this case, the unpredictable slow offset drift of the device leads to a significantly worsened detection limit. The dependence of the sensitivity on ambient humidity further deteriorates the accuracy, so that the usability of a classical PID without GC in practice is highly limited.

We present a new PID design that eliminates the offset and thus offset drift problems and reduces the cross-sensitivity to humidity. It is based on an additional grid that allows modulation of the ion flow in a part of the ionization chamber. This modified PID exhibits a 20 times improved detection limit and a reduction of the cross-sensitivity to humidity from 58% of the signal to 10% of the signal. Further reduction is possible.

Language: English

Document Type: Miscellaneous

Affiliations: 1: Current address: Philips Centre for Industrial Technology, Sensors and Measurement, PO Box 218, SAQ-p 320, Eindhoven, The Netherlands. To communicate with the author use: M.Liess@gmx.net.

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