Читать книгу Continuous Emission Monitoring - James A. Jahnke - Страница 131

Visible light is used in opacity monitors, where the peak and mean spectral response is required to be between 500 and 600 nm, with less than 10% of the peak response below 400 nm and above 700 nm. This “photopic” region is established so as to be within the visual range of human observing stack exit opacity. Tungsten lamps, green light emitting diodes, and lasers have been used for this application, however green light emitting diodes are the most commonly used today.