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SediMeter™
Measures...
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Patented Sensor and Customized Logger
The SediMeter™ sediment instrument is ideal for measuring sedimentation rate, both in terms of sediment accumulation rate, and in terms of sediment settling from suspension. The SediMeter™ reports backscatter values even within the accumulated sediment, why sediment compaction can be detected from the data. This makes it possible to measure also erosion, scour, and resuspension, and distinguish them from compaction. Compaction is of course mostly an issue with cohesive sediment.
The SediMeter™ instrument consists of a computer and a sensor. This sedimeter sensor consists of an array of 36 infrared optical backscatter detectors. The turbidity is measured every 10 mm, and the bottom level is estimated to 0.1 mm in the post-processing software. The sensor is controlled by the LogDator™ computer, which is also available separately as an under-water data logger.
A temperature sensor is included, and two optional sensors can be fitted, e.g., pressure and light. These sensors can be sampled many times per measurement. Potential uses include measuring wave frequency spectra (wave period), and cloudiness.
Model SM2A can be used both as a stand-alone logger and connected to a cable. It has USB, RS-485 (EIA-485, TIA-485), user interface, built-in memory, accepts SD/MMC memory cards, and runs on batteries or external power. The computer software for setup, download, data analysis, real-time monitoring, and internet server, is free. An RS-485 network with hundreds of instruments can be controlled from one computer.
Designed for Cost-Effective Measurements & Monitoring
The instrument is designed based on long experience in collecting and analysing sedimeter data. The goal is overall cost-effectiveness in small as well as large organisations, taking into account all associated costs—not just the price. In environmental monitoring it can be used for continuously measuring the accumulation of sediment spill on sensitive bottoms.
Helcom recommends that monitoring of the sedimentation pattern be mandatory during marine dredging. A network of SediMeters can be used for that purpose as described in our sedimentation monitoring plan. As an example of criteria, the accumulation of sediment spill on mussel banks around Saltholm in Øresund is limited to 10 mm at any given time (i.e., 15 kg/m2). The SediMeter with its resolution of better than 0.1 mm is an attractive choice for such sediment spill monitoring.
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“...recommending that sedimeters be installed to monitor sedimentation on reef tracts..."
Coastal Engineering Administrator in Florida Department of Environmental Protection
"...dredge monitoring ... there is not much out there that is as simple and cost effective."
Senior Environmental Scientist in an engineering consulting company
Application Example: Spill Monitoring
Click to open these photos in a new window (design subject to change; some photos on this page show non-standard features):
The SediMeter reports turbidity in the unit FBU. It is a kind of Formazin Turbidity Units (FTU), similar to the ISO 7027 standard of FNU (Formazin Nephelometric Units). The difference is that the scattered light is measured at 180 degrees rather than 90 degrees, and that the near infrared (NIR) wavelength is 945 nm rather than 860 nm. The somewhat longer wavelength helps decrease the influence of ambient light, as does a new measuring and compensation procedure. The ISO standard—as well as the US standard with unit NTU—of 90 degree scatter are incompatible with measuring very high concentrations—they would report low concentration values rather than high when buried or in thick turbidity currents.
