Instruments and Systems: Monitoring, Control, and Diagnostics Annotation << Back Turbidimeters with variable gauge length O.V. MELNICHUK, V.S. FETISOV Various problems in the field of liquid media turbidity measurement are reviewed, such as in-line turbidimiters errors caused by dirtying on windows of its optical elements and the problem of wide dynamic range of turbidity. The brief review of the known technical solutions intended for solving the mentioned problems is presented. The idea to adapt gauge length (distance between a light source and a photodetector) of turbidimeters for current values of turbidity with the purpose of error minimization is stated. Proposed turbidimiters are able to realize the automatic recognition of situations when photodetector signal decrease is caused by dirtying of optical elements windows rather than by increase of turbidity of medium. Such solution allows to switch on a cleaning device according to critical degree of windows dirtying. Some results of mathematical modeling are presented. Key words: turbidimeter, ratiometric principle, variable gauge length. Е-mail: melnichukov@mail.ru, fet777@rambler.ru