Measuring pond water depth from the surface?

abreuma

I'd like to build a floating device to measure water depth from the surface.· Probably a range of 2 to 30 feet but maybe not even that deep.· I haven't stumbled on a good sensor or example of this with a BS.· Seems like it would be easy to find a used fish-finder, cut the water sensor off and interface to a BS.· Does anyone know how those work?

John R.

In essence, they are "Ping [noparse]:)[/noparse]))" sensors. Unfortunately, most of the smarts is usually in the fish finder, not in the actual sensor. This means that you'd have to generate the signal wave, listen for the return, and do the timing to determine the depth. I'm guessing a Stamp is not fast enough for that.

There are some high end (i.e. expensive) "network based" systems where each sensor conditions and then transmits it's readings. These are normally targeted at the "yachting" market (both wind and propeller driven), and are probably not in the price range you're looking for.

I am also interested to see if anyone else as any ideas on this topic.

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John R.
Click here to see my Nomad Build Log

ElectricAye

abreuma said...
I'd like to build a floating device to measure water depth from the surface. Probably a range of 2 to 30 feet but maybe not even that deep. I haven't stumbled on a good sensor or example of this with a BS. Seems like it would be easy to find a used fish-finder, cut the water sensor off and interface to a BS. Does anyone know how those work?

If the pond isn't lined with rocks or cement, you might find that an ultrasonic sensor might have trouble indicating a firm bottom. If there is a lot of debris and ooze, etc. on the pond bottom, your signals might not return as cleanly as you'd wish, and this would be especially problematic for shallow depths. Just something to keep in mind.

sailman58

If you could work with a fixed installation, then use a donut shaped float around a pipe embedded in the bottom. That way you can measure the distance from the sensor at the top of the pipe to the float and subtract from the total length, probably an easier nut to crack!

Ron

Searider

You could also point a Ping sensor down at the surface of the water from a known heigth above the bottom of the pool. Same technique as the donut idea but more gagety.

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Searider

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Larry~

This is a pond?
how much does the depth change?
How do you need to get the info to a computer or go out and get reading?
what is the shore line like, a simple stick close to shore with markings on it would work once depth is measured!
you could use pressure sensors on a 1/4 inch tubing with a weight on the end, a piece of string with a weight on the end.
you could have a string with a weight on the end pulling an encoder wheel and measure the pulses.
make someone go down with the dumb end of a tape measure.

ElectricAye

I'm thinking out loud here: maybe place a pinger at a fixed depth, aim it upwards and measure sound waves bouncing off the water/air interface.

I don't know where your pond is located, but think about ice if it gets that cold sometimes.

If you need high resolution, then you probably need to go with some of the methods others have already mentioned here (floats, etc.) but bear in mind what the wind might do to a float.

fullspeceng

I do a lot of diving and have a depth finding sonar for $100 that I use to find depths while Kayak Diving for Lobsters in Southern California:
http://www.leisurepro.com/Prod/AQUDSS.html

It works fine.

Maybe you can hack it or in worst case read the LCD signals.

BradC

Drop a small pvc pipe in with a weight on one end. Have a sealed pressure sensor on the other end and measure the air pressure.

From my SCUBA days about 3M is one atmosphere, so as a pressure differential 0PSI = no water, 15PSI = 3M and so on..

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If you always do what you always did, you always get what you always got.

kwinn

Brad, a good idea which I tried on a water storage tank. Problem is the air dissolves in the water and eventually the readings are off. You need either a very thin bladder to separate the air and water or a small air pump to displace the water from the tube. I used a windshield washer pump on a timer that ran for a few minutes once a day.

John R.

Here's a couple interensting links:

Fish finder with wireless remote sensor (about $150)

Handheld Depth/Fish finder - might be hackable and only about $60

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John R.
Click here to see my Nomad Build Log

Post Edited (John R.) : 11/13/2009 4:23:22 PM GMT

Phil Pilgrim (PhiPi)

Here is a "smart" depth transducer that outputs an NMEA (4800 baud serial) sentence, similar to what you'd get from a GPS.

-Phil

Nightflight

A couple of links that may be of help/interest... could be adapted for use with parallax microcontrollers I think.· I've been working on my own fish finder using a Lowrance transducer (available separately from the sonar unit).· Want to do more than just the depth measurement though.· Actually want to see suspended objects (a.k.a. fish, structure, etc).

transducer interface (word description only but can be followed)
http://www.sxlist.com/techref/io/sensor/sonar.htm

sonar steered robotic fish (short range solution I'd imagine, since transducer is not excited by a large voltage signal)
http://www.seattlerobotics.org/encoder/200211/autonomous_robotic_fish.html

Nightflight

Duffer

This does not involve a sensor as you had imagined (like a sonor), but depending on your requirements, it might do the job.

A float with an arm of the appropriate length could be anchored or weighted at the bottom of the pond and a pivot devised at the float. Because you know the length of the hypotenuse (the arm) and you can measure the angle of the arm with a shaft encoder or rheostat, calculating the depth under the float is just solving for the side of a right triangle. sin of the angle times the hypotenuse gives you the length of the side under the float or the depth.

Variations in the bottom surface, materials used for the arm and variances caused by wave motion would have to be filtered out, but I think it would work depending on the accuracy that you require.

Duffer