Turbidity Analyser uses light in the near-infrared (NIR) range from 730 to 970 nm. A precisely defined, constant light beam penetrates the liquid sulphur. Light scattered from particles in the medium is detected by eight hermetically-sealed silicon photodiodes at an angle of 11°. Simultaneously, the unscattered light is detected by a reference photodiode. If sulphur turbidity reaches an unacceptable level, the flow can be automatically recirculated or switched off.