Current Meter: How to Measure Average Velocity of Flow by Current Meter

(Last Updated On: 02/08/2018)

A current meter is flow measuring device to measure the flow by mechanical or electrical means.

To Measure Average Velocity of water flow, Different Methods can be used in hydraulics engineering. Out of that Pitot tube is already covered in below post.

 Read: Important Tube Gauges Which Are Used to Measure Fluid Pressure

Here I will cover “Current Meter” which is used to Measure Average Velocity of Flow.

This Average Velocity of Flow is required to Measure the River Discharge.

Read: How to Calculate the Discharge Flow of River

current meter

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  • So, Here is the details about Current Meter

It consists of a Wheel containing Blades or Cups which are Rotate by the Flowing Water.

An Electric Current is supplied to Wheel by means of Wire.

A Rotation of Wheel makes and breaks the Electric Circuit, so it causes an Electric Bell to Ring.

Hence the Velocity of Flowing Water is obtained by counting the ringing of the Bell, the Rotation at Wheel.

The Current Meter is suspended by means of a fine cable and lowered to the required Depth.

Hence the Current Meter is free to move about its Horizontal and Vertical Axis.

So that it can adjust itself to the Direction of Water Flow.

  • Rating of Current Meter

So, the process of obtaining the relationship between the number of Electric Signals, Transmitted from Current Meter in unit time, and the Velocity of Flowing Water, Flowing past the Meter is known as the Rating of Current Meter.

By Rating Curve or Rating Table, we can directly obtain the Velocity of Water with the corresponding Signals.

  • Precautions for Rating of Current Meter

01) The Water in the Rating Tank must be allowed to come completely to rest. It should happen after each run and beginning of the next.

02) The Current Meter must not be allowed to approach too closely to the sides or bottom of the Rating Channel.

03) The Rating Channel should not be less than 2 meters wide and 1.5 meters deep. It should be long enough to permit a clear run at a Constant Speed of at least 15 meters.

04)The Current Meter should be supported by the same type of Rod or Cable, which is intended to be used during the Velocity observations in Field.

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