Compensation of excitation light intensity in automated UV detector for sulfur dioxide monitoring

The fluorescence method is one of the excellent analytical methods for monitoring sulfur dioxide in the atmosphere. However, it has several instrumental problems such as zero drift, span drift and stability. The reasons for these problems are the decrease in the incident light intensity of xenon lamp with time and the fluctuation of its pulse-to-pulse intensity. In the present study, we have developed a compensation system consisted of following three components: 1) a monitor by silicon photodiode for incident light intensity, 2) an analog memory for monitoring intensity, and 3) a divider unit. The system has reduced zero and span drifts by about five times compared with those without it. The results have been theoretically discussed.