A thorough analysis of sediment dynamics requires the use of precise, high-frequency particle size distribution (PSD) and suspended sediment concentration (SSC) measurements.
Since sediment transport processes can unfold quickly and under shifting hydrodynamic circumstances, accurate in situ measurements are critical for capturing PSD and SSC fluctuations as they occur.
A submersible particle size analyzer measures PSD and SSC directly in the water column, minimizing artifacts and delays caused by discrete sampling. The essential characteristics of a submersible particle size analyzer can help establish its applicability for a specific application.
When these characteristics are compatible with field requirements, such an analyzer can maintain accuracy and stability even as turbidity, flow, and pressure conditions change in real-world aquatic environments.
Key Features of Submersible Particle Size Analyzers
Measurement Range
A good submersible particle size analyzer must detect the entire range of particles found in natural water bodies. The measurement range should be between 0.1 µm and 2000 µm for clay particles, sand grains, and aggregates.
Key Considerations:
- Particle size range- The particle size range is broad enough to include both fine and coarse sediments.
- Suspended sediment concentration (SSC) range- The suspended sediment concentration (SSC) range should be reliable for clear and turbid water, ranging from 0.001 to 100 g/L.
- Measurement consistency- The submersible particle size analyzer must provide consistent results, even when particle densities, concentrations, and flow conditions vary.
A submersible particle size analyzer gives accurate, comparable results in dynamic environmental circumstances due to its large measurement range.
Optical Measurement System
The optical system installed in the analyzer determines how well it detects and classifies particles.
Submersible particle size analyzers often use techniques such as laser diffraction to determine particle size from the angular distribution of scattered light, yielding stable and quantifiable particle size distributions even when sediment loads change rapidly in the field.
Key Features:
- Laser source- A stable, monochromatic laser (usually 635 nm, 10 mW) provides consistent illumination.
- Detector array- A multi-angle detector array with 80 detectors covering 0.0163 ° to 42 ° allows for accurate size resolution.
- Optical path length- Adaptive path length systems adjust to changing turbidity levels, enabling accurate measurements when sediment concentrations fluctuate.
A well-designed optical arrangement determines the submersible particle size analyzer's precision and durability, especially in dynamic, sediment-rich environments.
Depth Rating and Structural Design
Field conditions can be unpredictable, and a submersible particle size analyzer must function reliably under pressure and temperature changes.
What Matters Most:
- Depth rating- The depth rating of the submersible particle size analyzer should surpass the maximum projected deployment depth, with 200 m being a reliable standard for field performance.
- Pressure stability- Hydraulic pressure-compensation chambers and sturdy optical support structures can maintain alignment with rising hydrostatic pressure.
The optical and electronic components of the submersible particle size analyzer are protected by its strong structure, which enables its steady, long-term operation and reliable measurements during extended deployments.
Anti-Fouling and Window Maintenance
Fouling by algae, sediment, and biofilm is one of the most challenging issues in underwater optical measurement, especially for a submersible particle size analyzer. Without mitigation, it rapidly degrades data quality.
Key Features:
- Automatic optical window cleaning- Integrated wipers or scrapers remove deposits during operation.
- Low-maintenance design- Reduces manual cleaning requirements during long deployments.
These features are essential for reliable field performance because clean optical windows help preserve constant data accuracy and save maintenance downtime.
Integrated Environmental Sensors
Integrated environmental sensors enhance the capabilities of submersible particle size analyzers by providing contextual information, such as depth, temperature and conductivity.
Key Integrated Sensors:
- Depth sensor- Provide the vertical position information required for profiling conditions throughout water layers
- Temperature and conductivity sensors- Measure temperature and conductivity of the water to assess water mass properties.
By combining particle and environmental information, users can not only track changes in PSD and SSC, but also monitor commonly used environmental parameters such as depth, temperature, and conductivity.
Data Handling and Power Management
The feasibility of deploying a submersible particle size analyzer in the field is determined by its effective data handling and energy efficiency.
Key Features:
- Onboard data storage- Supports autonomous, long-term monitoring.
- Multiple communication options- Wired, 4G wireless, and offline transmission modes give users more options for accessing, transferring, and managing acquired data.
- Low power consumption- Enables longer deployment without recharge or maintenance.
Well-designed data and power systems in submersible particle size analyzers lessen operating demands while increasing the productivity of each monitoring attempt.
Precision Begins with the Right Analyzer
Image Credit: Bettersize Instruments Ltd.
The features of a submersible particle size analyzer determine its capacity to produce accurate results in dynamic aquatic situations.
Bettersize Instruments' DeepSizer 300 submersible particle size analyzer, with its superior optics, durable structural construction, and integrated environmental sensing, illustrates the capabilities required for constant in-situ sediment analysis.
Using a polarized 635 nm laser and an 80-detector array, it monitors particle sizes ranging from 0.1 to 2000 µm and suspended sediment concentrations from 0.001 g/L to 100 g/L, allowing for small fluctuations in particle populations.
Differential Path Technology and Adaptive Path Technology maintain stable data quality as turbidity levels change, while automated window cleaning ensures optical routes remain clear throughout extended deployments. All of these features provide accurate measurements in challenging settings.
This information has been sourced, reviewed, and adapted from materials provided by Bettersize Instruments Ltd.
For more information on this source, please visit Bettersize Instruments Ltd.