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LISST Instruments >
LISST-SL
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Sequoia Scientific, Inc. has developed a laser diffraction system for measuring sediment properties in rivers and streams, the LISST-SL (for StreamLine).
The streamlined body is a minimum drag shape. Twin fins below the body orient the LISST-SL facing upstream before insertion. A pitot static tube on top of the body measures river velocity.
The system employs active control of the intake pump that matches river velocity to intake velocity making the sample acquisition isokinetic. Diffracted light is measured in an enclosed electro-optics test section.
Data are transmitted up the USGS B-reel to a ‘topside’ Control Box, equipped with a touch panel display showing depth, temperature, velocity, mean grain size and total concentration in real-time. The detailed size distribution and volume concentration can recovered by offloading and processing the data stored onto the topside control box.
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Depth, velocity, and temperature arestored with each sample. With the included depth data, the system iscapable of delivering sediment flux in the river. Not only is itpossible to measure the total flux; since the LISST-SL measures theconcentration in each of 32 size bins it is possible to measure thesize-dependent flux of suspended sediment across the entire transect.
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Upon startup the touch panel display will initialize the instrument and load instrument-specific calibration files.
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On the Main Menu there are three options: Calibrate (in order to acquire a zscat measurement), Measure (starts a profile), and Setup.
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A step-by-step instruction on how to obtain a zscat with the LISST-SL is displayed. The user must check all three boxes before the 'Collect Background' button appears.
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As soon as the 'Measure' button is pressed the LISST-SL will start sending data to the topside control box. The data are partially processed in order to show total volume concentration and mean grain-size, together with depth, velocity and temperature. The units displayed can be changed from English to Metric in the Setup Menu.
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The Setup Menu allows the user to set the instrument clock, change units, list files and delete files.
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Setting the clock is done via the keypad.
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Units for depth and velocity are changed by pressing the button. The data from the instrument are saved in an ASCII file, ready for import into Excel. The units in the ASCII file will change according to which button was selected when a profile was started.
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A list of the files that have been saved can be accessed from the Setup Menu.
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Related Links
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The system was first successfully fieldtested in June 2004. The first unit was shipped in 2005. For features,details, and preliminary specifications, please download the brochureor
email us
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LISST-SL brochure.
LISST-SL paper.
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2010 NWQMC 7th Nat'l Monitoring Conference
Denver, CO, 25-29 April 2010, booth 304
USGS Nat'l Data Conference
Omaha, NB, 11-13 May 2010
Joint 9th FIS and 4th HMC Conferences
Las Vegas, NV, 27-20 June 2010, booth 207
9th annual StormCon
San Antonio, TX, 2-4 August 2010, booth 421
Ocean Optics XX
Anchorage, AK, 25 September - 1 October 2010
CASQA 6th annual conference
CA, 1-3 Novemb | | |
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