Turbidity Sensors (0 to 4000 NTU)

How a turbidity sensor works

Most water turbidity sensors shine light into the sample and measure how much scatters at 90° to the beam, the principle behind NTU (Nephelometric Turbidity Unit). More suspended particles scatter more light, so the 90° signal rises with cloudiness. Exner's NIR process sensors work differently: absorption sensors measure how much near-infrared light passes straight through, while backscatter sensors measure light reflected back toward the source, both suited to higher-concentration food and beverage streams where a 90° scattered-light sensor would saturate.

How to choose a turbidity sensor

• Range: the S461-LT covers 0 to 10 or 0 to 100 NTU at 0.01 NTU resolution for low-turbidity water such as drinking water or filtered process streams; the S461-TN extends to 4000 NTU for higher-turbidity applications; the Ultra Low Turbidity Sensor targets 0 to 10 NTU specifically for drinking water and swimming pools.
• Measurement method: use 90° scattered light for clear-to-moderate liquids, backscatter (EXspect 271) for high-turbidity or opaque streams, and absorption (EXspect 231) for concentration monitoring in food and beverage.
• Process fit: EXspect 291 reads 0 to 200 NTU or 0 to 50 EBC, useful where a food or beverage process reports in EBC rather than NTU.
• Compact vs standard: EXplore 131 and 171 are compact water-turbidity sensors where space is limited, using the same 90° scattering principle as the S461 series.
• Application: drinking water and filtration duty need low-range, high-resolution sensors; brewing, juice and dairy lines suit the Exner NIR sensors, which read in EBC or FAU as well as NTU.

For solids concentration in heavier sludge streams, see Suspended Solids Analyser.