Last edited by Mitaur
Sunday, May 3, 2020 | History

2 edition of in Situ Optical Beam Attenuance Meter. found in the catalog.

in Situ Optical Beam Attenuance Meter.

Canada. Atlantic Oceanographic Laboratory. Bedford Institute.

in Situ Optical Beam Attenuance Meter.

by Canada. Atlantic Oceanographic Laboratory. Bedford Institute.

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Published by s.n in S.l .
Written in


Edition Notes

1

SeriesCanada Bedford Institute Report bi -- 1973-03
ContributionsLarsen, E.
ID Numbers
Open LibraryOL21892855M

The scattered flux F(θ) can be expressed as a function of the optical assembly parameters of the scattering meter: F (θ) = I (θ)Ω e – cr, (3) where Ω is the viewing solid angle of the photodetector (sr), c is the beam attenuation coefficient (m –1), and r is the distance between the center of the scattering volume and the. Absorption and Attenuation Coefficients Using the WET Labs ac-s in the Mid-Atlantic Bight: Field Measurements and Data Analysis eBook: NASA, National Aeronautics and Space Administration: : Kindle StoreAuthor: National Aeronautics and Space Administration NASA.

Book 1, Collection of Water Data by Direct Measurement. Techniques and Methods 1–D5. Conceptual diagram demonstrating the attenuation of a beam of radiation by. of the principles can be applied to other in situ optical sensors for water-quality studies. Monte Carlo simulations are used to establish a weighting function that describes the collection of angular scattering for the WETLabs AC-9 reflecting tube absorption meter. The equivalent weighting function for the AC-9 attenuation sensor is found to be well approximated by a binary step function with photons scattered between zero and the collection half-width angle contributing to the.

1. Introduction. The volume scattering function (VSF) β(ψ) (units of m −1 sr −1), describes the angular distribution of light scattered from an incident unpolarized VSF and the volume absorption coefficient α(λ) (m −1), provide the most fundamental description of a medium's inherent optical properties (IOPs), as all other IOPs can be derived from them [1–5]. The updated Monte Carlo scattering correction provides excellent agreement with independent absorption and attenuation measurements made with a point-source integrating-cavity absorption meter (PSICAM) and a Laser In Situ Scattering and Transmissometer (LISST, Sequoia Scientific), respectively.


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In Situ Optical Beam Attenuance Meter by Canada. Atlantic Oceanographic Laboratory. Bedford Institute. Download PDF EPUB FB2

Stimulated. in situ fluorescence as well as the beam attenuation coefficient at nm were measured respec- tively with a Sea Tech fluorometer (Bartz et al. ) and a cm-pathlength Sea Tech transmissometer (Bartz et al.

Measurements were also made with prototype. However, in the early days of optical oceanography, it was difficult to measure in situ IOPs other than the beam attenuation coefficient.

On the other hand, it was relatively easy to measure radiometric variables such as the upwelling and downwelling plane irradiances. spectral absorption and beam attenuation meter in the clear natural waters of the Sargasso Sea and to validate these measurements against independent, in situ apparent optical property (AOP) and in vivo IOP determinations.

The development of methodologies for making accurate IOP profiles for this highly demanding environment will lead to an. The design, construction, and use of an oceanographic instrument which measures in situ the optical beam attenuance coefficient of sea water in the range of to m-1 for any one of six defined spectral bands is described.

The instrument is readily calibrated using pure water and has been designed to maintain its calibration over a period of several weeks despite lamp changing and the shocks Cited by: 6. A A A = a --aw ~- Ap+Bv+Ay (3) An optical beam attenuance meter, equipped with interference light filters and a 2o cm cell path length, was used to measure attenuance coefficients at selected wavelength bands of 45o-5oo nm (reported as nm) and 66o-7o0 nm (reported as nm).Cited by: Optical techniques for remote and in-situ characterization of particles pertinent to GEOTRACES Emmanuel Bossa,⇑, Lionel Guidib, Mary Jo Richardsonc, Lars Stemmannd, Wilford Gardnerc, James K.B.

Bishope, Robert F. Andersonf, Robert M. Sherrellg a School of Marine Sciences, Aubert Hall, University of Maine, Orono, MEUSA bLaboratoire d’Oceanographie de Villefranche (CNRS. In the ac-9, the detector for measurement of has an acceptance angle of about 1 deg, and the detector for measurement of has an acceptance angle of about 40 deg.

Another way to account for scattering in absorption measurements is to place the entire measurement chamber inside an integrating sphere. The simple principle of the beam transmittance or attenuance meter is to produce a parallel beam of light, which, after passing a water path of fixed length, impinges on a detector, usually a photocell.

The performance of the meter is improved by high collimation of the beam. With an optical system of the type shown in this chapter, the divergence is minimized so as to become negligible. Assuming a conversion factor to beam attenuation of m 2 g −1 (based on the compilations of Gardner et al.,Hill et al., ), the lowest and average c p at nm are expected to be of the order of m −1 and m −1, respectively.

Oceanographic lidar profiles compared with estimates from in situ optical measurements Article (PDF Available) in Applied Optics 52(4) February with Reads How we measure 'reads'. The emphasis of our research is to develop methods for making accurate and precise IOP measurements made with a WETLabs AC-9 spectral absorption and beam attenuation meter in the clear natural waters of the Sargasso Sea and to validate these measurements against independent, in situ apparent optical property (AOP) and in vivo IOP determinations.

The principle of a beam transmittance or attenuance meter is to produce a parallel beam of light, which, after passing a water path of fixed length, impinges on a detector, usually a photocell.

The performance of the meter is improved by high collimation of the beam with an optical system of the type. The calibration of beam attenuation meters by means of a water standard measured with a two-pathlengths device is discussed.

It is shown that the particulate scattering to attenuation ratio can be assumed to be constant to the same accuracy that the shape of the volume scattering function can be assumed to be constant in sea water.

An optical Solution for Simultaneous in-situ Sea Water Salinity and Turbidity Measurements. several issues impact the laser beam attenuation measurement, while the measurement of salinity is. Inherent Optical Properties Measurements and Protocols: Beam Transmission and Attenuation (v) is a document that serves as a comprehensive overview of beam transmittance concepts and the calibration, measurement and analysis protocols for the state-of-the-art technologies that measure the attenuation of dissolved and particulate matter in water.

F(u) can be expressed as a function of the optical as-sembly parameters of the scattering meter: F(u) 5 I(u)Ve2cr, (3) where V is the viewing solid angle of the photodetector (sr), c is the beam attenuation coefficient (m21), and r is the distance between the center of the scattering vol-ume and the photodetector (m).

The irradiance E in Eq. The design and calibration of a proposed in situ spectral absorption meter is evaluated using a laboratory prototype. The design includes a silver coated (second-surface) glass tube, a tungsten light source (stabilized by means of optical feedback), a monochromator, and a solid state detector.

The device measures the absorption coefficient plus a portion of the volume scattering function. Winters, G. & Buckley, D. In situ determination of suspended particulate matter and dissolved organic matter concentrations in an estuarine environment by means of an optical beam attenuance meter.

In-situ particulate optical scattering. Bulk beam attenuation coefficients at nm (c()) were measured with an ac-s spectrophotometer (WETLabs, Seabird-Scientific) for underway samples (AMT Laser In Situ Scattering and Transmissometer (LISST) attenuation data, with the two instruments having in-water scattering collection angles of ; and ; respectively.

Several studies have examined various aspects of the absorption and attenuation meter designs including optimization of flow-tube diameter and reflecting ma. WET Labs underwater absorption and attenuation meters (ac-9 and ac-s) measure both the spectral beam attenuation [c (lambda)] and absorption coefficient [a (lambda)].

The ac-s reports in a continuous range of nm with a band pass of 4 nm, totaling approximately 83 distinct wavelengths, while the ac-9 reports at 9 : Nobuaki Ohi.The beam attenuation serves as a proxy for particulate matter and is a key parameter in visibility algorithms for the aquatic environment.

It is well known, however, that the beam attenuation is a function of the acceptance angle of the transmissometer used to measure it.

Here we compare eight different transmissometers with four different acceptance angles using four different deployment.attenuation in the wavelength region between and nm. The meas-urement is performed in situ, with-out sampling or sample pre-treatment, thus preventing errors due to sampling, sample transport and storage etc.

A measurement cycle takes between 20 and 60 s, making possible a high meas-uring frequency and detection of rapid changes.