Cross-sensitivity evaluation for ammonia sensing using absorption spectroscopy in the UV region

This paper describes an optical sensor for the monitoring of ammonia gas. An open path optical technique is used to analyze the absorption lines of ammonia within the ultra-violet region. The optical sensor shows absorption lines comparable to the theoretical ammonia spectra. Cross-sensitivity with carbon dioxide and oxygen gas has been tested and clearly shows that these two gases have no effect on ammonia measurement in the ultra-violet region, between 200 nm and 230 nm. The optical sensor is able to detect ammonia down to 9 ppm with an average error less than 2%. The optical sensor system also shows a fast response time which is less than 4 s.