When designing a transmissometer or a laser diffraction-based sensor for particle size analysis, an important consideration is the beam acceptance angle.
A transmissometer will measure a – generally small – portion of the forward scattered light: The light that is scattered away from the beam but still within the acceptance angle of the detector. Thus, the transmittance is overestimated, resulting in an underestimated beam attenuation coefficient. This error depends on the optical elements and design of the transmissometer. There is no standard for transmissometer acceptance angle, and each manufacturer may use a different acceptance angle for a particular design. This begs the question: What determines the best detector acceptance-angle choice for a transmissometer design?
Read the – perhaps surprising – answer in our article here!