The weaker beam is collimated and passed through a reference cell containing a high concentration of the target gas before being focused onto the reference detector. This ensures that the laser is locked to the adsorption line of the target compound. The stronger beam then passes through an optical multiplexer to permit multipoint sampling. To maximize sensitivity, two tone FM modulation techniques are used. To enhance detection, the signal sampling sequence involves multiscan averaging.
Extensive software supports data acquisition, display, and analysis.
For absorption paths of a few hundred meters, sensitivities are in the parts per billion range and are somewhat reduced for the shorter path length involved in stack detection. Unisearch Associates Inc. Unisearch Associates Inc. manufactures spectroscopic instruments including FTIR and chemi-luminescence instruments, for environmental monitoring and process control. The company was established in 1080, initially commercializing research from York University. Unisearch operates fully equipped electro-optical laboratories, as well as manufacturing facilities in Toronto, Ontario. Unisearch also provides contract research and development and measurement services to industrial and government clients.