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  • Testing Sequoia’s LISST-­Holo on an Autonomous Underwater Vehicle | Sequoia Scientific
    augmented sensing for interdisciplinary research The April experiment provided an opportunity to test how LISST HOLO may augment sensing capabilities for interdisciplinary research with AUVs Experiment Description The study region is strongly influenced by wind driven coastal upwelling which supplies cold nutrient rich waters to the bay and promotes the growth of microscopic algae Figure 1 Figure 1 Experiment description The map left shows a filament of upwelled water extending across the mouth of Monterey Bay The boxes in the track of AUV Dorado indicate frontal locations identified by AUV Tethys frontal position changed with time Vertical sections of water column properties right are shown for the upper 40 m along the Dorado survey track The April experiment utilized two AUVs in efforts to map and sample the different water types and the boundary front between them AUV Tethys a long endurance AUV autonomously monitored frontal locations and provided this information to AUV Dorado which was equipped with a water sample acquisition system and a larger sensor payload including LISST HOLO The AUVs described environmental and biological changes influencing the detection of microscopic life by a moored autonomous molecular analytical device the Environmental Sample Processor ESP see map in Figure 1 LISST HOLO was deployed on AUV Dorado Plankton diversity imaged by LISST HOLO during the survey shown in Figure 1 is illustrated in Figure 2 A key research goal of the experiment synthesis is to understand the different plankton populations that develop in different water types as well as the frontal zones between them For this purpose information from LISST HOLO images is being integrated with data from other AUV sensors Figure 1 as well as results of molecular analysis of water samples acquired by the AUV Figure 2 A LISST HOLO diversity montage from the Dorado AUV survey

    Original URL path: http://www.sequoiasci.com/article/testing-sequoias-lisst-%c2%adholo-on-an-autonomous-underwater-vehicle/ (2016-02-13)
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  • What are the concentration limits for the LISST-HOLO? | Sequoia Scientific
    limits for the LISST HOLO LISST HOLO concentration limits Sequoia June 7 2011 The article LISST Concentration Limits describes how to compute the upper concentration limits for the LISST instruments However the results in that article does NOT apply to Sequoia s LISST HOLO instrument because the minimum optical transmission that is allowable for the LISST HOLO is 0 8 80 whereas it is 0 3 30 for the rest of the LISST instruments So what are the concentration limits for measurements with the LISST HOLO instrument These can be computed in the exact same manner as outlined in the LISST Concentration Limits article but using an optical transmission of 0 8 instead of 0 3 This yields the following maximum concentrations in mg l for a LISST HOLO with a 50 mm optical path Sauter Mean Diameter Wentworth Grades Maximum Concentration µm Phi mg l 1 95 9 00 Clay 8 3 9 8 00 Very Fine Silt 15 7 8 7 00 Fine Silt 31 15 6 6 00 Medium Silt 62 31 25 5 00 Coarse Silt 123 62 5 4 00 Very Fine Sand 247 125 3 00 Fine Sand 494 250 2 00 Medium Sand 987 Questions to this application note Email us Last Updated 12 11 2011 More in Library Library Articles Technical Papers Standards Our Newsletter Sign up to get the latest news on Sequoia and our products Home Products Product Overview LISST Instruments LISST 100X LISST ABS LISST Portable XR LISST Holo LISST Deep LISST StreamSide LISST STX LISST Hydro LISST Infinite LISST VSF LISST STOKES Optical VSF Sensors LISST SL LISST 25X FlowControl Instruments FlowControl Lab FlowControl Sub Radiative Transfer Models EcoLight S HydroLight Accessories How to Buy Request a Quote Terms Of Sale Support FAQ Downloads Warranty Info Installation Requirements

    Original URL path: http://www.sequoiasci.com/article/what-are-the-concentration-limits-for-the-lisst-holo/ (2016-02-13)
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  • Are some LISST-STX size classes more reliable than others for computing sediment excess density? | Sequoia Scientific
    then we can t get the total suspended sediment concentration by multiplying the volume concentration with the density Why does the concentration in a size class not drop to 0 The standard time for a full settling experiment is 22 hours this should normally ensure that all particles in the column have settled out However if the duration of an experiment is shortened to less than 22 hours then only some size classes will have time to settle out Hence no estimate of settling velocity thus density and TSS of the remaining size classes It can also happen that even if the settling experiment is 22 hours long some particles are still in suspension This is particular so during the summer and in waters with a high biological productivity where small pieces of algal detritus and living and or dead biological matter may be in suspension Such material has a density much lower than then 2650 kg m3 that is commonly used for mineral grains often just a little bit higher than that of the water itself 1050 kg m3 If the particle density is so low then the particles simply will never settle out For example as a rule of thumb a particle with a diameter of 33 micrometer settles roughly at 1 mm s if it is a mineral grain Such a particle has an excess density of 1600 kg m3 2650 kg m3 1050 kg m3 A biological particle with an excess density of e g 50 kg m3 1100 kg m3 1050 kg m3 settles a factor of 1600 50 32 times slower 0 03 mm s Consequently if the smallest size classes in the LISST STX have just a small fraction of biological material in them then the particles will probably not settle out until

    Original URL path: http://www.sequoiasci.com/article/are-some-lisst-stx-size-classes-more-reliable-than-others-for-computing-sediment-excess-density/ (2016-02-13)
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  • LISST concentration limits | Sequoia Scientific
    limit We must first compute the optical transmission t associated with the concentration limit It is usually recommended that the lower value for the optical transmission is 30 or 0 3 for the LISST Portable XR the minimum recommended is 75 or 0 75 Fortunately the relationship between t and c is given by Beer s Law t exp c L c ln t L where L is the pathlength in m Now for a standard LISST 100X with a path length of 5 cm 0 05m we can compute the beam attenuation coefficient for tau 0 3 c ln 0 3 0 05 24 and thus we find that for a an optical transmission of 0 3 the beam attenuation coefficient will be 24 m 1 This value then becomes our c in equation 1 above and if the particle size is 100 µm we have the following 24 1 13 SSC 100 SSC 24 100 1 13 2124 mg l For a particle size of 33 µm we find SSC 24 33 1 13 700 mg l as expected since the maximum concentration scales linearly with diameter The LISST 100X can be equipped with a path reduction module that decreases the optical path to 1 cm instead of 5 cm and we can now compute what the maximum concentration is in this case Tau is still 0 3 so in order to find the associated c we have c ln tau L ln 0 3 0 01 120 m 1 and for a 100 µm particle we find the concentration to be SSC c d 1 13 120 100 1 13 10 600 mg l 1 The LISST StreamSide has a path length of 5 mm 0 005 m which means that c ln 0 3 0 005 241 m 1 For a particle size of 33 µm we find that the concentration limit is SSC c d 1 13 241 33 1 13 7038 mg l What about the lower concentration limit It is generally recommended that the optical transmission does not exceed 98 0 98 For this value of tau c ln 0 98 0 005 4 m 1 for the LISST StreamSide For 33 µm particles the minimum concentration is therefore c d 1 13 4 33 1 13 116 mg l for 10 µm particles the minimum concentration is 35 mg l Tables The table below shows the maximum theoretical mass concentration in mg l equivalent to PPM by MASS that the LISST would be able to measure as a function of mean particle size in µm and optical path length varying from 50 mm standard LISST 100X to 3 mm standard LISST Infinite Note that the LISST Portable XR has a different transmission limit 75 instead of 30 from other LISST instruments so this figures in this table do not apply to it See the LISST Portable XR Specifications for details Mean particle diameter Wentworth grades LISST Optical Pathlength in mm µm Phi

    Original URL path: http://www.sequoiasci.com/article/lisst-concentration-limits/ (2016-02-13)
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  • LISST Technology Shows What Turbidity Measurements Miss out in a River Profile | Sequoia Scientific
    are blind In reality their sensitivity decreases inversely as grain size d increases i e as 1 d The data below illustrate this The data were acquired during tests of the LISST SL instrument conducted by the USGS at the Cowlitz river bridge in Castle Rock WA USA This instrument employs laser diffraction technology to measure size distribution and concentration The left panel optical transmission equivalent to turbidity shows an apparently vertically mixed water column over the water depth The second panel shows velocity which has a decrease nearer river bed The third panel shows the concentration which unlike turbidity now reveals an increasing concentration toward the river bed Red circles in this panel show data from P 61 physical samples taken by Kurt Spicer USGS at the same time showing a good match The average concentration increases three fold toward the bed again without any indication in turbidity The last panel explains why It shows the particle size distribution with depth The color bar on right shows concentration The horizontal axis is grain size in F units 2 5 to 500 µm It emerges that a vertically constant wash load exists at size F 6 16 µm Coarse particles at F 2 do not exist at the surface but their concentration increases with depth so much so that it dominates the total concentration at the deepest point Because these particles are large turbidity is less sensitive to them and therefore the turbidity signal remains constant throughout All rivers exhibit such vertical structure a structure first described by Rouse in 1937 Turbidity sensors do not respond to it and laser diffraction clearly explains why Furthermore in this case turbidity would be interpreted as a vertically constant concentration whereas in reality concentration increased 3 fold near the bed Finally note the

    Original URL path: http://www.sequoiasci.com/article/lisst-technology-shows-what-turbidity-measurements-miss-out-in-a-river-profile/ (2016-02-13)
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  • LISST-SL velocity thresholds | Sequoia Scientific
    LISST SL Does it need a minimum flow speed in order to sample What is that Absolutely The internal pump in the SL will adjust the intake velocity to match the ambient flow speed in order to make the sample intake isokinetic However it is necessary to maintain a minimum pump velocity in order to avoid settling of particles inside the instrument This cut off velocity where the pump velocity will start to exceed the ambient stream flow speed is 0 5 m s The pitot static tube will still function at speeds lower than 0 5 m s but the sample becomes less and less isokinetic at flow speeds lower than 0 5 m s More in Library Library Articles Technical Papers Standards Our Newsletter Sign up to get the latest news on Sequoia and our products Home Products Product Overview LISST Instruments LISST 100X LISST ABS LISST Portable XR LISST Holo LISST Deep LISST StreamSide LISST STX LISST Hydro LISST Infinite LISST VSF LISST STOKES Optical VSF Sensors LISST SL LISST 25X FlowControl Instruments FlowControl Lab FlowControl Sub Radiative Transfer Models EcoLight S HydroLight Accessories How to Buy Request a Quote Terms Of Sale Support FAQ Downloads Warranty

    Original URL path: http://www.sequoiasci.com/article/lisst-sl-velocity-thresholds/ (2016-02-13)
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  • Operating principle of the LISST-25 constant calibration sediment sensor | Sequoia Scientific
    light scattering by particles It permits separating the scattering from large vs small particles based on the radius where the light appears This is the property that is employed for particle sizing in all our LISST instruments The second property behind the design of the LISST 25 relates to the magnitude of light scattering for a given volume of particles Larger particles not only scatter into small angles as described above they also produce less scattered energy per unit particle volume than smaller particles As an example a single particle of size 100 microns would scatter far less light at its characteristic small angle than 8 particles of size 50 microns would at their characteristic twice larger angle although they have an equal combined volume Any sediment sensor should produce an equal photocurrent for equal volumes of particles regardless of size The LISST 25 achieves this by use of shaped detectors Since smaller particles produce disproportionately large amount of light at large radii the detector is shaped so that light is sensed over a smaller fraction of the full annulus at the larger radius This idea leads to a decreasing angular width of the photo active annulus away from the center This is the origin of the comet shaped particle volume sensor Figure 2 Total particle area concentration is sensed in a similar way but on a separate detector As particles of all sizes produce nearly the same amount of light per unit particlearea in an annulus at their corresponding radius scattering angle on the detector there is only a small variation in the width of the annulus at different radii This produces the nearly constant arc width wedge shaped detector for total area sensing This is seen as the upper detector in Figure 2 Note that the hole in the center of the detector passes the focused laser beam through unobstructed A separate conventional photodiode senses the power in this beam The optical transmission is estimated from the ratio of the magnitude of transmitted laser power in the presence of particles with its value in clear water The accuracy of the estimate of sediment concentration and the estimate of the mean diameter is of fundamental interest This is performed at two levels In theoretical simulations it is possible to synthesize the angular scattering on the face of the detector This simulation is done with assumed Gaussian particle size distributions The mean and standard deviation of the simulated size distribution is varied from the narrowest to the broadest in equal phisize increments The LISST 25 measures particles in the size range of 1 25 250 microns2 The simulation is implemented by dividing this size range into 32 equal phi size bins From the simulated scattering on the face of the detector the response of the special detectors is computed for the estimated mean size and the estimated concentration These parameters are normalized to the corresponding simulated input values so that ideally these ratios should be equal to 1 In Figure

    Original URL path: http://www.sequoiasci.com/article/operating-principle-of-the-lisst-25-constant-calibration-sediment-sensor/ (2016-02-13)
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  • LISST-Portable|XR Videos | Sequoia Scientific
    Conference 2014 Customer List Newsletter Contact Sequoia International Distributors Sequoia Scientific New Product LISST ABS Log In Register Home Products LISST Portable XR Videos LISST Portable XR Videos Below is a list of videos related to the LISST Portable XR Particle Size Analyzer The videos are separated into different groups Introduction How to LISST Portable XR How to make a measurement Advanced Topics More in Products Products LISST Portable XR Videos LISST Portable XR Videos Accessories How to Buy Request a Quote Request Submitted Terms Of Sale Our Newsletter Sign up to get the latest news on Sequoia and our products Home Products Product Overview LISST Instruments LISST 100X LISST ABS LISST Portable XR LISST Holo LISST Deep LISST StreamSide LISST STX LISST Hydro LISST Infinite LISST VSF LISST STOKES Optical VSF Sensors LISST SL LISST 25X FlowControl Instruments FlowControl Lab FlowControl Sub Radiative Transfer Models EcoLight S HydroLight Accessories How to Buy Request a Quote Terms Of Sale Support FAQ Downloads Warranty Info Installation Requirements Responsibilities Warranty Register a Product Returns Contact Support Library Articles Technical Papers Standards About Staff News Events PiE Conference 2014 Customer List Newsletter Contact Sequoia International Distributors News More News PiE 2016 Conference to

    Original URL path: http://www.sequoiasci.com/products/lisst-portable-xr-videos/ (2016-02-13)
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