hi! we're making a project that can monitor moving water in a river. I wonder if there is any sensor that could measure the velocity and speed of the water in the river?
A web search for "water speed sensor" or "water velocity sensor" turns up several commercial offerings.
Hint: velocity is speed, with added direction indication.
The river water right at the edge of the bank does not move. Water in the deepest part move fastest. What part of the river are you measuring and how are you anchoring your sensor so it does not move?
A paddlewheel on a float that slides up/down on a post.
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Memorize for your uni years:
Speed is a Scalar with one component; Magnitude.
Velocity is a Vector with two components; Magnitude and Direction
For your project, two ideas.
- pick two points of a known distance. Start a timer and drop a float at the start. When the float reaches the end, stop the timer. Calculate distance over time.
- place a bicycle front fork and wheel in the water with just the bottom of the wheel touching the water. Place eight or nine fins on the wheel (depending on 32 or 36 spokes) so at least two fins are in the water. Secure a bolt-and-nut onto one spoke that will contact a counter attached to the fork each rotation. Use the diameter of the wheel, number of revolutions (distance) and time.
- Tie a string to a float. Release the float and start a timer. Stop the timer at the end of the string. Calculate the known distance over the measured time.
Depending on the location of the measurement especially close near shore, the direction changes or even reverses due to tides.
Furthermore, if there are things in the water there will be rotating waters, or slightly sideways.
And as said above the water has different speeds, side vs middle, deep shallow etc.
What is the goal of measuring the velocity?
What do you calculate or conclude from the numbers your get?