The design principle of TD-200 adopts tungsten filament lamp light source, and TD-201 adopts 400-700nm visible LED light source. The measurement principle of 90 degree scattering Angle conforms to EPA and IS07027 specification. Precision optical window, with optical compensation, automatic bubble removal, sand settling principle design to ensure long-term stability and accuracy of measurement. Suitable for turbidity monitoring of tap water, terminal water, reuse water, swimming pool, R0, pure water, etc.