OPTIMISATION OF A POLARISATION NEPHELOMETER

作     者：Oshlakov, Victor G. Shcherbakov, Anatoly P. 

作者机构：RAS Siberian Branch VE Zuev Inst Atmospher Opt Tomsk Russia 

出 版 物：《LIGHT & ENGINEERING》 (Light Eng.)

年 卷 期：2021年第29卷第2期

页      面：87-95页

核心收录：

主　　题：polarization nephelometer non-isotropic scatterer scattering matrix elementary volume elementary light beam approximation error LED encoder microprocessor precision position control motor power bridge pulse-width modulation PID controller 

摘      要：An analysis of the influence caused by polarization nephelometer parameters on the scattering matrix measurement accuracy in a non-isotropic medium is presented. The approximation errors in the actual scattering volume and radiation beam by an elementary scattering volume and an elementary radiation beam are considered. A formula for calculating the nephelometer base is proposed. It is shown that requirements to an irradiation source of a polarizing nephelometer, i.e. mono-chromaticity and high radiation intensity and directivity in a wide spectral range can be satisfied by a set of high brightness LEDs with a radiating (self-luminous) small size body. A 5-wavelength monochromatic irradiation source, with an emission flux of (0.15-0.6) W required for a polarization nephelometer, is described. The design of small-sized polarizing phase control units is shown. An electronic circuit of a radiator control unit based on an AVR-Atmega 8-bit micro-controller with feedback and drive control realized by means of an incremental angular motion sensor and a software PID controller 2 is presented. Precise and smooth motion of the radiator is ensured by standard servo-driven numerical control mathematics and the use of precision gears. The system allows both autonomous adjustment of the radiator s reference positions and adjustment by means of commands from a personal computer. Both the computer and microcontroller programs were developed with the use of free software, making it possible to transfer the programs to Windows-7(10), Linux and embedded Linux operating systems. Communication between the radiator s position control system and the personal computer is realised by means of a standard noise immune USB-RS485 interface.