The optical system of a turbidimeter consists of a tungsten filament lamp, a 90° detector for monitoring scattered light, and a transmitted light detector. Modern turbidimeters feature diverse optical path designs, including those employing scattering methods for turbidity measurement and unique 360° × 90° optical path designs. The instrument's microprocessor calculates the signal ratio from the 90° detector and the transmitted light detector. This ratio calculation technique corrects for interference caused by chromaticity and/or absorbing substances (such as activated carbon) and compensates for the effects of light intensity fluctuations, providing long-term calibration stability. The optical system design also reduces drift light, improving test accuracy.
In addition to traditional tungsten filament lamps, modern turbidimeters also use LED light sources, infrared light sources (such as near-infrared light with a wavelength of 880 nm), and even lasers as light sources. Some instruments employ a dual-beam design, automatically compensating for errors caused by light source attenuation, optical window contamination, and temperature drift by comparing the measured light signal with the reference light signal in real time. These designs aim to improve measurement accuracy, long-term stability, and adaptability to a wider range of sample conditions.
