| 摘要 |
<p>An improved method and apparatus for monitoring particulates in stacks or ducts(2) utilizes transmissometer/particulate monitor of the type which has an optical assembly containing a solid state light source (30) of visible light such as a light-emitting diode or a solid-state laser. The light source (30) emits a collimated beam that is split, part of which is focused onto a reference detector (33) that monitors the intensity of the light source, while the other part is directed to a beam-steering apparatus that causes the beam to accurately pass through a gaseous sample to a desired location such as a retro-reflector (20). A position-sensing detector (32) is used in a closed-loop manner to control the beam-steering apparatus. The ratio of the total energy of the detected light beam, relative to the reference detector output, is used to determine the opacity of the gaseous sample for the purpose of providing a basis for correlation to particulate loading of that portion of the particulates that are of a size comparable to the wavelength of light. The correlation to particulate loading is enhanced by a feature of the invention which measures the angular distribution of forward-scattered light to provide information as to the particle size distribution of the particulates. In addition, by steering the beam such that the intensity of scattered light at a preferred scattering angle of 2 to 3 degrees is measured, a measurement may be made that provides a signal that is proportional to the total concentration of particulates independent of the size distribution. <IMAGE></p> |
