Photo-ionization detector for volatile gases

摘要

The PID includes an ultraviolet (UV) lamp for transmitting a UV light through an optical window into an ionization chamber to ionize volatile gases. An ion detector is disposed in the ionization chamber to detect the produced ions. The ion detector comprises a pair of interdigital electrodes which produce an electrical field that is perpendicular in direction to that of the UV light propagation. A pump is also incorporated into the PID to circulate gases into and out of the ionization chamber. The direction of the circulation is perpendicular to the direction of the electrical field as well as the direction of the UV light propagation. Because the aforementioned directions are perpendicular to each other in three dimensional space, the ion detector of the present invention may be sensitive to concentration ranges up to about 10,000 ppm of ionizable gases.