Abstract: A device that eliminates the baseline instability of Atomic Absorption Spectroscopy monitors by utilizing a dual-source, dual-beam optical configuration. The source of one beam, the measuring beam, is light emission from a hollow cathode lamp which is used to determine the atomic vapor density by conventional atomic absorption principles. The second source, the calibration beam, is an emission which has negligible absorption by the atomic vapor, and passes through the same optical path as the measuring beam. For each light source, one beam passes through the processing chamber before its intensity is analyzed. The intensity of a second beam is determined near the light source to provide a reference signal for ratio measurement. Using conventional signal processing, the atomic vapor density, and thus the deposition rate, can be precisely determined despite changes in light source intensity, window transmission and optical alignment.

Abstract: A method and apparatus for determining the amount and size of particles and bubbles in a liquid process medium. The invention comprises the steps of providing a collimated light source to generate a light beam of a known wavelength, and directing it to illuminate a liquid sampling volume within a cell positioned within a sensor housing constructed to collect the light scattered by particles and/or bubbles within the sample caused by the impingement of the light beam. The scattered light is then separated into forward, and/or right angle and back scattering portions, and converted into separate electrical signals for each scatter direction. Since the scattering coefficient is a direct function of the density of the sampling volume, the presence of bubbles reduces the density and the amount of radiation scattered in the backward direction.