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261:, floating dock or fish pen. Tilt current meters have the advantage over other methods of measuring current in that they are generally relatively low-cost instruments and the design and operation is relatively simple. The low-cost of the instrument may allow researchers to use the meters in greater numbers (thereby increasing spatial density) and/or in locations where there is a risk of instrument loss.
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similar, but the housing is designed such that the meter hangs from the attachment point. In either case, the housing tilts as a function of its shape, buoyancy (negative or positive) and the water velocity. Once the characteristics of a housing is known, the velocity can be determined by measuring the angle of the housing and direction of tilt. The housing contains a
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Travel time instruments determine water velocity by at least two acoustic signals, one up stream and one down stream. By precisely measuring the time to travel from the emitter to the receiver, in both directions, the average water speed can be determined between the two points. By using multiple
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scattered back from particles within the water column. The ADCPs use the traveling time of the sound to determine the position of the moving particles. Single-point devices use again the
Doppler shift, but ignoring the traveling times. Such a single-point Doppler Current Sensor (DCS) has a typical
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that records the orientation (angle from vertical and compass bearing) of the Tilt
Current Meter. Floating tilt current meters are typically deployed on the bottom with a lead or concrete anchor but may be deployed on lobster traps or other convenient anchors of opportunity. Sinking tilt current
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Tilt current meters operate under the drag-tilt principle and are designed to either float or sink depending on the type. A floating tilt current meter typically consists of a sub-surface buoyant housing that is anchored to the sea floor with a flexible line or tether. A sinking tilt current is
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consisting of an anchor weight on the ground, a mooring line with the instrument(s) connected to it and a floating device to keep the mooring line more or less vertical. Like a kite in the wind, the actual shape of the mooring line will not be completely straight, but following a so-called
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Travel time meters are generally more accurate than
Doppler meters, but only record the velocity between the transducers. Doppler meters have the advantage that they can determine the water velocity at a considerable range, and in the case of an ADCP, at multiple ranges.
235:), it is possible to evaluate the variability of the averaged horizontal flow by measuring the induced electric currents. The method has a minor vertical weighting effect due to small conductivity changes at different depths.
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is used to estimate the through-flow through the gateway and the complete setup can be seen as one huge current meter. The physics behind: Charged particles (the ions in seawater) are moving with the
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Marchant, Ross; Stevens, Thomas; Choukroun, Severine; Coombes, Gavin; Santarossa, Michael; Whinney, James; Ridd, Peter (2014). "A Buoyant
Tethered Sphere for Marine Current Estimation".
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if the top buoy is above the sea surface) the shape of the mooring line can be determined and by this the actual depth of the instruments. If the currents are strong (above 0.1
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Lowell, Nicholas S.; Walsh, David R.; Pohlman, John W. (2015). "A comparison of tilt current meters and an acoustic doppler current meter in vineyard sound, Massachusetts".
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Mechanical current meters are mostly based on counting the rotations of a propeller and are thus rotor current meters. A mid-20th-century realization is the
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There are two basic types of acoustic current meters: Doppler and Travel Time. Both methods use a ceramic transducer to emit a sound into the water.
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Dewey, Richard K. (1 December 1999). "Mooring Design & Dynamics—a Matlab® package for designing and analyzing oceanographic moorings".
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which drops balls into a container to count the number of rotations. The
Roberts radio current meter is a device mounted on a moored
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524:"Mooring Design & Dynamics - A Matlab Package for Designing and Testing Oceanographic Moorings And Towed Bodies"
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This article is about a type of oceanographic instrument. For an instrument to measure electric current, see
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Propeller-type current meter. The revolutions of the propeller per time interval are counted electronically.
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velocity range of 0 to 300 cm/s. The devices are usually equipped with additional optional sensors.
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current meters rotate around a vertical axis in order to minimize error introduced by vertical motion.
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in the magnetic field of the Earth which is perpendicular to the movement. Using
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526:. Centre for Earth and Ocean Research, University of Victoria. Archived from
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Doppler instruments are more common. An instrument of this type is the
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2015 IEEE/OES Eleventh
Current, Waves and Turbulence Measurement (CWTM)
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or a non-anchored ship's actual position to the position predicted by
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paths, the water velocity can be determined in three dimensions.
382:. Atlantic Oceanographic & Metereological Laboratory at NOAA
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and transmits its findings via radio to a servicing vessel.
356:. National Oceanography Centre, Southampton. Archived from
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A buoy deploying a
Roberts radio current meter, c. 1960
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Lagrangian and
Eulerian specification of the flow field
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by mechanical, tilt, acoustical or electrical means.
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This novel approach is for instance employed in the
403:"New England/Mid-Atlantic | NOAA Fisheries"
380:"Florida Current Transport - Project Background"
16:Device for measuring the flow in a water current
290:) and the mooring lines are long (more than 1
269:Current meters are usually deployed within an
294:), the instrument position may vary up to 50
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340:relevant passages online at Google Books
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66:is located, this is the basics for the
242:Tilt Current Meter Operating Principle
401:Fisheries, NOAA (September 1, 2021).
326:C. Reid Nichols, Robert G. Williams,
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74:: The observer can be either in the
481:IEEE Journal of Oceanic Engineering
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177:Acoustic Doppler current profiler
124:passing a resting current meter.
96:measure the displacement of an
354:"Monitoring the MOC at 26.5°N"
328:Encyclopedia of Marine Science
58:, one distinguishes different
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587:Oceanographic instrumentation
562:10.1016/S1369-9350(00)00002-X
342:, accessed online 01-26-2012.
330:(2008), Infobase Publishing,
257:meters may be attached to an
186:over a depth range using the
179:(ADCP), which measures the
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229:Faraday's law of induction
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50:Different reference frames
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448:10.1109/CWTM.2015.7098135
278:. Under the influence of
221:submerged telephone cable
217:electromagnetic induction
207:Electromagnetic induction
501:10.1109/JOE.2012.2236151
378:Meinen, Christopher S.
62:depending on where the
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582:Physical oceanography
271:oceanographic mooring
259:oceanographic mooring
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493:2014IJOE...39....2M
233:Maxwell's equations
154:Ekman current meter
148:Rotor current meter
522:Dewey, Richard K.
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80:Lagrangian drifter
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457:978-1-4799-8419-0
352:Duchez, Aurélie.
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556:(1–4): 103–157.
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192:sound waves
42:device for
576:Categories
534:2012-09-25
364:2012-09-18
314:References
184:velocities
142:Mechanical
92:Lagrangian
82:) or in a
78:(as for a
487:(1): 2.
466:32839642
302:See also
276:catenary
168:Acoustic
162:Savonius
120:measure
116:Eulerian
64:observer
509:2832210
489:Bibcode
274:(half-)
122:current
101:drifter
56:physics
21:ammeter
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215:where
38:is an
505:S2CID
462:S2CID
282:(and
129:Types
452:ISBN
407:NOAA
388:2012
332:ISBN
284:wind
247:Tilt
158:buoy
105:buoy
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