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公开(公告)号：US3805074A
公开(公告)日：1974-04-16
申请号：US32040173
申请日：1973-01-02
Applicant: TEXAS INSTRUMENTS INC
Inventor： MC CORMACK K
CPC classification number: G01N21/3504 , G01N21/39
Abstract: An apparatus for monitoring air pollution sources, such as, for example nitrous oxide (NO), sulphur dioxide (SO2), or sulphur trioxide (SO3) is disclosed. The apparatus includes a tunable diode laser as a transmitter of infrared energy. The diode laser is tuned in a periodic fashion such that the laser light emission wavelength is scanned through an absorption line of a pollutant gas. The tuning effect is produced by driving the diode laser with a current which is the sum of a d.c. and an a.c. current. The laser energy is transmitted to a beamsplitter. The beamsplitter divides the energy between a sample path and a reference path. The sample path may be an open air path or include a sample cell; the reference path contains a cell having a known concentration of the pollutant gas being monitored. A chopper is provided to alternately sample the radiation passing the sample and reference cells to a detector which produces an a.c. signal whose peak to peak difference value contains the information of the difference in concentration levels of the contaminant in the reference and sample paths. A feedback circuit is provided to feed-back a d.c. current, equivalent to the time difference between the offset in the center point of the diode emission and the center of the contaminant absorption line, to the laser drive circuit to provide automatic lock onto the center of the contaminant absorption line.
Abstract translation: 公开了一种用于监测空气污染源的装置，例如一氧化二氮（NO），二氧化硫（SO2）或三氧化硫（SO3）。 该装置包括可调二极管激光器作为红外能量的发射器。 二极管激光器以周期性方式调谐，使得激光发射波长通过污染气体的吸收线扫描。 调谐效应是通过以二次电流的总和驱动二极管激光器产生的。 和a.c. 当前。 激光能量传输到分束器。 分束器在采样路径和参考路径之间划分能量。 样品路径可以是露天路径或包括样品池; 参考路径包含具有被监测的已知浓度的污染气体的电池。 提供斩波器以将通过样品和参考细胞的辐射交替地采样到产生等离子体的检测器。 峰值差峰值包含参考和样品路径中污染物浓度水平差的信息。 提供反馈电路以反馈直流。 电流，相当于二极管发射的中心点的偏移与污染物吸收线的中心之间的时间差，提供给激光驱动电路，以提供自动锁定到污染物吸收线的中心。
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