Mobile distance measurement in water.

[grayt]

Looking for an existing production device or one that can be modified to alarm once a pre-determined distance between two devices has been exceeded.

Distance will be less than 50m.
Devices will be mobile.
Must function in salt water.
Accuracy +/- 10%
Smaller the better.

Other ideas welcome. (Am already reviewing

http://www.bluesoft-inc.com/)

 

[IRstuff]

sonar comes to mind...
Do both objects need to know?


TTFN

 

[grayt]

Both instances need to remain active and able to go into an alarm state if the other moves out of range. I have been thinking along the lines of short range wireless network or similar.

 

[IRstuff]

Radio does not propagate in salt water...

Were you intending to keep part of it above water?

TTFN

 

[grayt]

No it will be below water however than range can be reduced to about 20 meters. My understanding was it was a range limitation rather than a total inability to function.

My thinking was directed to wireless by the several manafacturers who are producting short range radio equipment for divers. (

http://www.suunto.com/pls/suunto/suunto2.pubmainpage.frameset)

as well as the some of the clubs I saw when researching, who are devoted to radio control Submarines (Fresh and Salt water)

Any ideas welcome however.

 

[joecontrol]

This may be to simple of an answer but here goes, why not a tether them with a coil on one end and a limit switch on the other end then it is adjustable. Well this is just a simple suggestion i am not sure if it is possible with the tether it may get in the way of what you are working with.


Well good luck,Joe

 

[toma]

Does it need to be a non-contact sensor? If not, I have a few ideas.

 

[wsmith]

Radio communications IS possible with submerged antennas but usually impractical for non-military use; a 2.4 GHz device certainly won't work. If you can use a floating wire antenna or better yet a whip antenna atop a float tethered to each of your underwater objects then the bluesoft product can be made to work. If this is not the case then you need an acoustic device.

Problem is most commercial acoustic positioning systems are likely overpriced and oversized for your application. The cheaper end of the APS market includes:

http://www.ore.com/lxt.htm

http://www.link-quest.com/

see TrackLink 1500LC

http://www.desertstar.com/newsite/positioning/pilot/pilot.html

The above products are designed for a surface ship to track range and bearing of one or several underwater targets rather than for two underwater vehicles to track each other. Note that false alarm rates and outliers can be high even with a top of the line APS.

Some diver hand held devices might be better suited to your application - one place to check is

http://www.rjeint.com/.

Dive Scan (

http://www.rjeint.com/pdf/dive_scan.pdf)

looks promising if you can overcome a few hurdles: need to aim in general direction of other target; must fiddle with the electronics to key on and if you want a digital output; and most importantly the other underwater vehicle must be big and reflective otherwise this device won't pick it up.

Do you have more details on your application to help narrow the search? Which radio controlled submarine clubs were you looking at?

 

[grayt]

The application is for disabled divers. Divers need to remain within a few meters of each other however disable divers and inexperienced divers pose special problems. The idea was to provide an audible alarm is 1 diver moved out of range of another.

I was going down the acoustic path and the links you provided were excellent.

One of the sites was

http://www.subcommittee.com/