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SediMeter SM3
The SediMeter measures a vertical turbidity profile and calculates sedimentation and erosion with millimetre precision.
Instrument for Sediment Monitoring: Siltation, Erosion, Scour, Deposition
The Lindorm SediMeter is a "sediment meter". It measures a 35 cm long vertical turbidity profile - using 36 optical backscatter detectors (OBS) - through the bottom, and calculates the level with micrometer resolution. The SediMeter is ideal for erosion and sedimentation measurements. The SediMeter can be used for detect when erosion happens, analyze siltation, and measure sedimentation rate, the latter both in terms of sediment accumulation rate, and in terms of sediment settling from suspension. It can be used to get real-time data on the dynamics of the sea floor, and it is ideal for monitoring sediment spill from dredging in real-time.
The patented sedimeter sensor consists of an array of 36 infrared optical backscatter detectors. The turbidity is measured every 10 mm, and the bottom level is interpolated with a resolution of 0.001 mm. This may seem like an exaggeration, but it allows for the detection of change on a very minute scale, and thus of qualitatively correlating processes (waves, currents, dredging spill) to sediment accumulation and erosion on the bottom. It has been found that the sedimentation of as little as 100 g/m2 can be detected (see this video).
There is also a dedicated 37th turbidity sensor mounted 11 cm higher up than the array of 36 OBSes. The calculated level, along with this turbidity, can be measured as "burst samples", up to 20 times for each measurement, at an interval of between 1 and 16 seconds. Thus the memory holds up to (20 x 16,384 =) 327,680 level and turbidity measurements. The turbidity data from the array of 36 OBSes is only saved once per measurement, though, and the same is true for temperature and battery data.
The SediMeter offers several deployment options. Both models, SM3A and SM3B, can be used either as a stand-alone logger, or connected to a cable, or both. The instruments support RS-485 at 9600 and 115,200 baud, and has a built-in rechargeable battery. The protocol supports daisy-chain networking, with hundreds of instruments along a single cable stretching over several kilometers. Radio telemetry can be used from a buoy to land, or via a satellite link. The required software is free.
Applications
Monitor... | In... | For... |
Sediment Accumulation | Channels | Navigation Safety |
Sedimentation | Bioherms | Dredging Spill Monitoring |
Siltation | Reservoirs | Environmental Monitoring |
Silt Deposition | Coral Reefs | Environmental Impact Assessment |
Resuspension | Lakes | Pollution Monitoring |
Scour | Rivers | Engineering |
Erosion | Shores | Environmental Management |
Near-Bed Turbidity | Seas | Research |
Common Specifications for SM3 |
|
Data | |
Data output | Turbidity at 36 + 1 levels (FBU), Bottom level (cm), Temperature (cK), Battery voltage (mV) |
Turbidimeter principle | 180° optical backscatter (OBS) |
OBS wavelength | 945 nm (NIR) |
OBS detectors | 36 for sediment level + 1 for turbidity and cleaner operation |
OBS spacing | 36 at 10 mm + one at 110 mm |
Bottom level accuracy | ±2 mm (for a well defined the bottom) |
Bottom level resolution | 0.1 mm |
Thermometer location | Between OBS #36 and #37 |
Thermometer resolution | 0.1°C, calibrated to ±0.5°C |
Logger | |
Measurement interval | User selectable from 1 second to 24 hours |
Burst samples | Up to 20 subsamples per measurement |
Burst channels | Level, and #37 turbidity |
Burst interval | 1 to 16 seconds |
Memory capacity | 16,384 measurements |
Communication | |
Computer interface | RS-485 (a.k.a. RS485, TIA-485) |
Baud rates | 9600 baud; 115,200 baud (9600,N,8,1 after RESET) |
Network | Up to 255 units in a daisy-chained cable |
Protocol | LogDator Communication Protocol ver. 3.0 |
Power | |
Input voltage range | 5 V ≤ Usupply ≤ 15 V |
Charge time | ca 16 to 20 hours |
Current, charging | Imax ≈ 110 mA |
Current, on-line monitoring | Iaverage ≈ 10 mA |
Battery life | Over one year |
Battery type | Lithium (NiMH on special order) |
User interface | |
Power status LED | Blue light when external power is connected |
Battery charging LEDs | Red for charging, green for full, both for error |
RS-485 LEDs | Yellow for listening, green for transmitting |
Measurement indicator LED | One blink per measurement |
Magnetic reed switches | Reset CPU; Battery charging error override |
Recommended accessories | |
Mounting hardware | Anchor, holder tube, and handle to screw it down |
Cable | USB to SediMeter cable, 1.8 m or 5.0 m standard lengths |
Blind plug | Protects UW connector when used stand-alone |
Software (free) | SediMeter.exe ver 3, and driver for the USB cable |
Environmental | |
Depth rating | 45 m (150') standard |
Temperature | From 0ºC to 50ºC, not exposed to direct sunlight |
Optical liquid medium | Purified saturated oil, odorless, combustible |
RoHS | *Lead in shuttle counterweight is exempt from prohibition |
Model versions
The SM3B is the first SediMeter with a built-in cleaner. This can enable it to operate for months on end, even in fouling environments.
Unique Specifications for SM3B |
|
Cleaner | Yes |
---|---|
Length | ca 760 mm |
Mass | ca 380 g + ca 230 g shuttle* |
Diameter | 15 mm sensor 20 mm motor house 60 mm shuttle |
Battery Capacity | 1800 mAh |
Connector | Bottom end |
The SM3A offers the slimmest SediMeter ever, the entire instrument fitting inside the holder tube, including logger, battery, and under-water connector.
Unique Specifications for SM3A |
|
Cleaner | No |
---|---|
Length | ca 700 mm |
Mass | ca 140 g |
Diameter | 15 mm |
Battery Capacity | 550 mAh |
Connector | Top end, under-water pluggable |