Measurement of the Opacity of Smoke and Suspensions under Ambient Lighting Conditions

Abstract

An entirely solid state photoelectric meter for the measurement of optical density is described. No light sealing arrangements are required, greatly simplifying the cleaning of the optical cell and facilitating the entry and exit of material when measurements are taken on flowing systems. Ambient light reaching the detector does not interfere with the measurements since the reference beam is coded. This beam is generated by a light emitting diode, avoiding many of the problems of conventional sources. The system has a wide application and its robustness should assure it a position in the field as well as the laboratory. Any change in the intensity of the reference beam can be measured, so the properties of transmissive, reflective or scattering systems may be measured.