Abstract
A laser-scattering particle size monitor for in situ measurements using optical fibers and two wavelength illuminations is presented. Using this monitor, we can obtain the signal that whether the measuring particle size is within the preset range or not, and whether it is larger or smaller than its range as being out of the range. The sensing head of this monitor is constructed to be compact and easy to handle because it can be set depart from the signal processing units and light sources.
The sensing head is composed of a light illumination probe and two pickup probes set at different angles to detect scattering lights. Two wavelength components of scattered light are detected simultaneously by each pickup probe and guided to a signal processing unit. In the signal processing unit, the value of the ratio of two scattered light intensities is obtained. Then, it is compared to the threshold value in order to get a binary output. The binary outputs obtained by two pickup probes form the binary code pattern, from which it can be determined that whether the particle size is within the desired range or not.
The characteristics of this monitor are discussed in terms of design parameters, such as a pickup probe setting angle and a wave-length difference of illumination lights. The operation of this monitor is confirmed by the experiments using polystylene latex spheres. As a result, it is shown that this particle size monitor is useful, for in situ particle size monitoring in industrial and medical fields.
