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Open-File Report 2005-1001

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U.S. Geological Survey Open-File Report 2005-1001
USGS East-Coast Sediment Analysis: Procedures, Database, and GIS Data skip menu

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Rapid Sediment Analyzer

Video Length: 1 minute, 53 seconds
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VIDEO FRAME
NARRATIVE
Full view of rapid sediment analyzer.
 The Rapid Sediment Analyzer, or RSA, is a settling tube suitable for the analysis of sand-sized material.
Close-up of rapid sediment analyzer.
 This model is equipped with a differential pressure transducer and calculates a size distribution based on the change in pressure with elapsed time. Other RSA’s are equipped with balances that can measure changes in weight with time.
Sample being introduced to micro splitter.
 A micro splitter is used to obtain a representative 7 to 8-gram subsample.
Sample placed in tablesppon being dampened with water.
 The sample is placed in a tablespoon and dampened with water by pipette to prevent trapped intergranular air from impeding the settling process.
Sample manually being spread into thinner layer on tablespoon.
 The sample should then be manually spread into a thinner layer to facilitate rapid disaggregation upon impact with the water surface.
Sample being introduced into settling tube of rapid sediment analyzer.
 Care must be taken to introduce the entire sample simultaneously into the middle of the settling tube. If the entire sample is not entered simultaneously, the sample will take longer to settle out of suspension and the calculated distribution will be finer than actually present. If the sample is not entered directly into the center of the settling tube, density currents may form along the tube wall allowing the sample to settle more rapidly and this results in a calculated distribution that is coarser than actually present.
view of sand grains settling in tube.
 The sand grains settle according to Stoke’s Law; pressure decreases as the grains settle past the lower transducer port.
View of analog signal recorded by computer.
 The analog signal from the transducer is amplified and logged on a computer equipped with an analog-to-digital converter. A typical analysis time is approximately 2 minutes.
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