My problem is that I need a sensor which is used to find the river bed depth. I tried using HC-SR04 ultrasonic sensor placed in air, the signal got reflected at air-water interface, working just like level detector. So I decided of placing the sensor in water to serve the purpose.
Can I place the sonar or ultrasonic sensor in water with waterproofing?
Will it give a solution to my problem?
I am also looking for some sort of material that is "transparent" to ultrasonic for waterproofing. Please recommend me a material that is transparent to ultrasonic.
I have tried with the latex rubber wrapped around the tx & rx. The ultrasound doesn't pass through the material. I have even tried whether the material is reflecting the ultrasound and it does reflect. Please suggest me with any other material that fetch a solution to the problem.
Place the ultrasonic sensor at one end of the stick, looking at the other end. Put the 'other' end into the water until it touches the bottom. Subtract the water surface measurement from the length of the stick and you will know the depth.
I used to work with a guy in charge of river measurements for a mining company. This is actually a seriously hard problem, if you want to measure with any accuracy for a period longer than a week. Even with a budget over 6 figures, it's a really difficult problem.
I need to measure the soil depth in order to know about the erosion (scour) that has taken place due to water flow of river around the pier or pillar of bridge.
Sorry for not mentioning this previously. What you said might be correct for still water. I don't think so the water level goes down if the soil is eroded. Generally the water level will be same even after erosion takes place .
Please suggest me if there are any other methods to solve this problem.
I don't think so the water level goes down if the soil is eroded.
Not entirely true, but the bottom level certainly does go down as soil is eroded, so the difference between "surface level" and "bottom level" increases.
The point about surface level is moot if someone builds a dam downstream, so perhaps a dock or other fixed structure would be a better reference.
I too like the idea. My requirement is for continuous monitoring of scour depth. I used the way he suggested with some support around the stick. It works well when the soil get eroded, means the stick had gone down. But when the soil settles back the stick never lifted up back again because of its own weight, which yields wrong results about scour depth.
However, I will be trying with some other material to find the solution. Please suggest me with any other ideas.
You need a hydrophone, or underwater ultrasonic transducer. Something made to be used in water.
An ultrasonic transducer is made to couple sound efficiently to and from air. Anything you do that ends up with it in water is going to be horribly insensitive.