Sonar help plz!!

[hotice121]

Hi all

I have been searching around everywhere trying to find information on writing a program to control a 200 kHz transducer through water but never really find much.

The kind of information I am trying to collect is the depth of the lake and what is on the bottom I believe this can be done by measuring the strength of the return echo.

I have found the following blog but i have read many different places that calculating through water is very differnt to air https://www.best-microcontroller-projects.com/pic-sonar.html.

I also believe you have to do some sort of calculation to remove any anomalies??

I have also found a bit of information on using IC's rather than a PIC to control the transducer but this will only give me time of the response and not the strength of the return echo...Unless im wrong.


Any help or sample code would be very much appreciated as im getting a bit stuck.

Many thanks for your time.

J

 

[ericgibbs]

hi and welcome.

Using a 200KHz sounder its fairly easy to measure water depth, but to determine the 'bottom structure' requires analysing more than just the strength of the echo.

If you download the pdf from this link it will give you a good insight into what you have to examine about the 'echo pulse' to give an indication of the reflecting surface structure.

A company called Roxann produced a 200KHz sounder that indicated the bottom conditions.
**broken link removed**

Whats the maximum depth of lake, is it fresh water or salt.??

https://www.google.co.uk/url?sa=t&r...Dy1mmKpGEhH6Oes-Q&sig2=0gc1De3M88niz775ptGXDw

 

[hotice121]

Hi thanks for the quick reply.

The maximum depth will be approx 25 meters and will always be in fresh water.

We want to be able to identify the following different types of bottom
-mud& sand
-gravel/hard bottom
-weed

 

[ericgibbs]

Hi thanks for the quick reply.

The maximum depth will be approx 25 meters and will always be in fresh water.

We want to be able to identify the following different types of bottom
-mud& sand
-gravel/hard bottom
-weed

hi,
A 200KHz transducer pulse power of approx 80Watts will give good depth results down to 80mtrs, this will allow a pulse rate of 10ppsec

For a depth of 25mtr, 40Watts at 20pps, with a pulse width of 100uS to 200uSec.

I know that the 'Roxann' system can differentiate between mud, sand and shingle bottoms,, [weed I have never tried.]

Read the pdf in that link and you will see that the 'echo' envelope does contain some information about the bottom conditions.

I would suggest you first build the 200KHz transceiver and then find 'bottoms' with the required parameters.
The receiver should have TGC [timed gain control] settings, to allow for the attenuation of the signal levels at increasing depths.

If you attach a scope or better still a echo sounder paper trace you will have a record of the different bottoms.

EDIT:
I should ask you what is the beam width of your transducer...?
8 degree is more for depth working and 2.5degree will give a sharper echo response [which you want]