Measuring turbidity below 0.1 NTU is genuinely difficult. The scattered light signal from a water sample at that cleanliness level is barely above the noise floor of most optical detector systems. Any drift in the detector's zero output — from temperature changes, from electronic noise, from trace contamination on the optical surfaces — shifts the apparent turbidity reading enough to produce negative values or meaningless oscillations. The HGY6098 addresses this through design choices in the optical system and through a zeroing protocol that needs to be correctly applied during unit startup and process transitions.

 

The optical geometry matters at low turbidity. A 90-degree scattering angle measurement is standard for turbidity instruments, but at sub-0.1 NTU the signal-to-noise ratio at 90 degrees is marginal on conventional detector designs. Instruments designed for ultra-low turbidity measurement use either a longer optical path length to increase the scattering volume, a more sensitive photomultiplier or avalanche photodiode detector, or a ratio measurement technique that compares forward-scatter to 90-degree scatter — the ratio is less sensitive to source intensity variations than either signal alone.

 

Zero-point drift from temperature changes is the primary source of reading instability at these concentrations. The detector's dark current — the signal it produces when no light reaches it — changes with temperature. If the instrument assumes a fixed dark current value and the actual dark current has drifted due to ambient temperature change, every turbidity reading is offset by the drift amount. At 10 NTU this offset is negligible. At 0.05 NTU it's the dominant error source.

 

The auto-zeroing procedure should be performed whenever ambient temperature has changed significantly, whenever the sample flow has been interrupted for more than a few minutes (which changes the optical surfaces' thermal equilibrium), and during each unit startup before the water quality readings are used for process control decisions. The procedure replaces the sample stream briefly with particle-free reference water — either deionized water from a separate source or the instrument's internal reference — zeros the detector output, then resumes sample measurement. The entire cycle takes less than two minutes on properly designed instruments and resets the baseline to current thermal conditions rather than to whatever temperature existed at the last manual calibration.

 

 

YOYIK, located in Deyang, Sichuan, is a comprehensive power station equipment and accessories company integrating R&D, manufacturing and sales. It is well-known in the industry for its exquisite craftsmanship and strict quality control. The company not only provides key components for thermal power and hydropower stations at home and abroad, but also involves in new energy fields such as wind energy and nuclear energy, showing strong innovation and adaptability. With customized services and global market layout, YOYIK has become a trusted partner of many large projects.

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DFYLMY-2026-06-04-A