Velocity measurement using current meter

This Presentation is an introduction to current meter device specially how to measure flow velocity using current meter,its types and methods used in field.

1. Velocity measurements Using Current-Meter

2. Contents of Presentation
•Defining Current-meter
•Common Types
•Principle of Current-meter
•Methods of Supporting for Current-meter
•Working and rating of Current Meters
•Method's of measuring Velocity
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

3. Current Meter ( an introduction)
•ThefirstcurrentmeterwasdesignedbyR.Woltmannin
1787.
•Acurrentmeterisaninstrumentusedtomeasurethevelocity
offlowingwater
•Acurrentmeterisoceanographicdevice(meansspecially
designedtoworkwithfluidsi.e.water
•Asitisfreeinwater,itcanadjustitselfinthedirectionof
flow
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

4. Current meters ( some common types)
Price type AA current meter on a
round wading rod ( depth ≥2.5ft)
Pygmy Current Meter (depth <2.5ft)
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

5. Some Other Types..
Electromagnetic Current Meters
•No moving parts
•Electromagnetic current meters produce voltage
proportional to the velocity
•Their use near metallic objects is still a limitation.
Original Woltmann Current Meter
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

6. Principle of operation
•Theprincipleisbasedupontherelationbetweenthespeedofthewater
andtheresultingangularvelocityoftherotor.
•Greaterflowvelocitymorerotationofpropellers
•Thenumberofrevolutionsoftherotorisobtainedbyvariousmeans
dependingonthedesignofthemeter
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

7. Methods of Supporting Current-meters
For Shallow depths
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

8. For Greater Depths
From Bridge From Boat
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

9. Via Cable and pulley
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

10. Electricallyoperatedcablecarwith
currentmeterandsoundingweight.
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

11. Working and rating of Current-Meters
‘’The rate of rotation of the wheel depends on the velocity of flow’’
Inordertodeterminethevelocityofthewaterfromtherevolutionsof
therotoroftherotating-elementcurrentmeter,arelationisestablished
betweentheangularspeedoftherotorandthespeedofthewaterwhich
causesittoturn.Thisrelationisknownasthecurrentmeterrating
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

12. Rating in Old Times
Bridgesdonotoftenoffertheright
conditionsforstreamgauging
RatingEquation
V=a+bn
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

13. •Anewtrendwasintroducedthenthemanufacturerusedtoprovide
ratingtablesandequations,itisstillused
•Byknowingthenoofrevolutionpersec(n)specificratingequations
areusedwhicharederivedbythemanufactureraftercertain
experimentationsontheproduct
Note:digitalCMareavailablenowwhichgivesthelinearvelocityofflowdirectly
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

14. Methods of Measuring Velocity
•One point Method Flow depth < 3m
•Two point Method Flow depth 3m-6m
•Three point Method Flow depth > 6m
Note:Other methods like five points and six points are also available
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

15. The 0.6 depth method
Velocity observations are made at a single point at 0.6 of the depth from
the surface and the value obtained is accepted as the mean
•The value of the method is its essential reliability, the ease and speed of setting the
meter at a single point
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

16. The 0.2 and 0.8 depth method
•Velocity is observed at two points at 0.2 and 0.8 of the depth from the
surface and the average of the two readings is taken as the mean
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

17. Three point method
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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar

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Presented By : Muhammad Bilal, Civil Engineering Dept UET
Peshawar