What is Turbidity
Turbidity is a measure of water clarity. Suspended particles—such as silt, algae, plankton, and sewage—can cause water to appear cloudy or murky. These particles scatter and absorb light, hindering its straight-line transmission through the water.
A higher turbidity value indicates a greater number of suspended particles, meaning the water is more opaque and “thicker.” Clear water has low turbidity levels.
Turbidity Measurement Methods
Nephelometric Method (Scattered Light):
- Detects scattered light. The detector is fixed at a 90° angle to the incident light source, capturing light whose direction has been changed by suspended particles.
- Highly sensitive for low-turbidity samples (e.g., drinking water, purified water). It precisely captures the scattering signal from small amounts of particles. Turbidity value is directly proportional to scattered light intensity.
Transmittance Method:
- Detects transmitted light. The detector is in line with the incident light source, capturing the direct beam that passes through the liquid without being blocked by particles.
- More responsive for medium to high turbidity samples (e.g., industrial wastewater, sewage). More particles cause greater attenuation of transmitted light, making this method suitable for quantifying high concentrations of suspended solids.
- Susceptible to interference from the liquid’s own color (colorimetric interference), as color can additionally absorb transmitted light. Common units are JTU (Jackson Turbidity Unit) or FTU.
Why Monitor Turbidity?
Measuring turbidity assesses the physical cleanliness and safety of a liquid by quantifying its suspended solids content. It is an essential foundational parameter in water quality monitoring, industrial processes, and scientific research.
Ensuring Water Safety:
- Turbidity is a key indicator for determining if drinking water and domestic water meet standards. High turbidity water may harbor bacteria, viruses, heavy metals, and other contaminants, increasing disinfection difficulty and posing direct health risks.
Controlling Industrial Process Quality:
- Many industries have strict requirements for liquid clarity. For example, high turbidity in pharmaceutical purified water or electronics ultra-pure water can lead to substandard drug purity or short-circuited electronic components.
Supporting Environmental & Scientific Monitoring:
- In environmental monitoring, measuring turbidity in rivers, lakes, and oceans helps determine if water bodies are affected by siltation, industrial effluent, or sewage, providing data to support ecological management.
How to Select a Turbidity Sensor
SPS-T-SC3 Low-Range Turbidity Sensor: Based on the 90° scattered light principle, it utilizes a laser light source with high parallelism and automatic intensity correction, paired with a high-sensitivity detector.
SPS-T-SC1 Turbidity / Suspended Solids (Sludge Concentration) Sensor: Based on 90° and backscatter light measurement principles for measuring turbidity and suspended solids.
SPS-T-SC4 Turbidity Sensor: Combines 90° scattered light measurement with the transmittance method for measuring turbidity and suspended solids.
Full-spectrum, multi-wavelength, и dual-wavelength sensors also typically use the transmittance method. These sensors are primarily suitable for medium to high concentration ranges and are not ideal for low-range turbidity monitoring. Notably, for treated wastewater that is relatively clean, the measured value may read zero, failing to provide a result.
Selection Comparison Chart:
| Product | SPS-T-SC3 | SPS-T-SC1 | SPS-T-SC4 | SPS-F / M / D |
|---|---|---|---|---|
| Точность | ±2% или ±0,015 NTU | ±5% or ±0.1 NTU | ±3% или ±0,015 NTU | ±3% или ±10 NTU |
| Диапазон | 0-100 NTU | 0-4000 NTU | 0-1000 NTU | 0-1000 NTU |
| Detection Limit | 0.005 NTU | 0.1 NTU | 0.02 NTU | 5 NTU |
| Принцип | Nephelometric | Nephelometric | Nephelometric + Transmittance | Transmittance |
| Установка | Flow-through | Submersible | Submersible | Submersible |
| IP Rating | IP65 | IP68 | IP68 | IP68 |
| Приложение | Питьевая вода | Wastewater / Surface Water | Wastewater / Surface Water | Untreated Wastewater |