Hi All,
I need to be able to measure distance underwater between points with a distance of 50 meter . So I'm thinking something as simple as a sonar should work. One sends a ping the other one receives it and replies back. Is this approach feasible? Can anybody recommend sonars I can use?
OR
any other solution.Please suggest

Thanks,
Ashok

 

hi ashok,
Go to your local yacht chandlers shop and look at the small 150KHz boat mounted transducers.
They will work ok over a 50mtr underwater distance.

Is it fresh or salt water.?
E

 

hi ashok,
Go to your local yacht chandlers shop and look at the small 150KHz boat mounted transducers.
They will work ok over a 50mtr underwater distance.

Is it fresh or salt water.?
E

Hi,

Thanks for reply,
We are not looking for ready made product.we are planing to design our custom board so can u suggest me any design circuits which we can implement.


Thanks,
Ashok

 

hi,
We need to know which type of transducer you plan to use and its frequency.
Also the required accuracy, pulse rate etc.... in fact we need a draft specification from you.

I did not suggest buying a ready made product, but a ready made transducer.
E

 

hi,
We need to know which type of transducer you plan to use and its frequency.
Also the required accuracy, pulse rate etc.... in fact we need a draft specification from you.

I did not suggest buying a ready made product, but a ready made transducer.
E

Hi,
i am not from RF background so don't know how to select transducer.
can u help on selecting transducer and addition circuit design like micro controller ,interfaces which is suitable for our project.
below attached our block diagram.
Thanks,
Ashok

 

hi,
You originally said 'sonar', which is ultrasonic sound, to measure distance between points.
Now you say RF , Radio Frequency to measure between multiple points.

I would recommend that you post a draft specification explaining the application and budget cost for the project.

E

 

As Errigibbs said, a spec would really help us to help you. Measurement under water can get quite complex depending on what it's for and how accurate you need to be. Measuring a depth from surface to seabed is quite straight forward, measuring a distance from point A on the seabed to point B on the seabed is way different. Using a 'ping' or sound bounce back time (sonar) will give you the distance of whichever object it hits first, it's also effected by the salinity (density) of the water, sound travels slower in fresh water and faster in salty water so an object 50m away may give you a distance return of 55m in fresh water and in salty 45m, also water density doubles for every 33 feet of depth. RF is rather more accurate but still wont give you exact distances point to point. The most accurate measurement is Ladar (sometimes known as LiDAR), which is basically laser radar, it works on the same 'bounce back' principle as sonar and RF but is way more accurate and not effected by water density.

 

Is it by any chance that the responding devices (I asume them sitting on the bottom) would be fitted with transducers?
If so, transducers certified for 50 meters depth. Those in the boats they are hardly submerged more than say one meter or two.

 

water density doubles for every 33 feet of depth

Not so. It's pressure that doubles. Water is not very compressible, so its density is practically constant unless under really extreme pressure.