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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
Video