Analog water level sensor? anyone?

[puuukeey]

Hi, I'm actually an engineer in a COMPLETELY different sense. I'm an audio/computer engineer. but I want to measure fluid waves for a creative application.

I was hoping someone could point me to a relatively cheap method of sensing fluid levels in the analog domain. I need to sense either 0 to14 ft or 0 to5 ft. depending on the context (pool or ocean) I need very accurate resolution. I'll take anything but sub millimeter would be preferable. I have a sensor input box, which takes 0-5v and I've done some research and the closest thing I can find is a 1300 dollar capacitive sensor which digitizes all of it's information.


I guess I'm kind of looking for the capacitive part and not the digital part.

anyone ever heard of something like this?

 

[sreid]

One way is to pump air down a tube and measure the air pressure with a pressure transducer. More details if this seems appropiate.

 

[puuukeey]

That is certainly an ingenious way to do it. I'm a bit turned off by the idea of putting something mechanically between the shape of the wave and the input but I does seem like it would logically work.

do you think I could accurately turn an ocean wave to sound (adjusting for speed of course) using this method?

 

[dpc]

What type of frequency range and response time do you want? Typically liquid level transducers try to smooth out the sloshing and wave action to determine an "average" level. Trying to measure sub-millimeter level over the ranges you indicate will put you down in the noise level for most off-the-shelf level transducer.

Typically for water, it is common to simply use a pressure transmitter to measure the water pressure, e.g.:

http://www.ttiglobal.com/Product.aspx?ProductID=18625

And if you spend a little time search Eng-Tips, you will find the longest thread in the history of instrumentation devoted to measuring down-hole level of a well or something (I'm trying to erase it from my memory).

 

[MacGyverS2000]

One word... lasers

Dan - Owner

http://www.Hi-TecDesigns.com

 

[melone]

Are you trying to measure the height of a moving wave in real time?

 

[jraef]

Ultrasonic level transducers are the answer for you. Their "filtering" can be turned down so that you can get raw data. No contact with the water, analog output, simple to implement.

Milltronics (now owned by Siemens) makes the best IMHO. To be fair, I am a Siemens employee but that is an entirely separate division. I used Milltronics for years long before Siemens bought them. 2 versions worth considering:

https://pia.khe.siemens.com/index.aspx?Nr=11159

https://pia.khe.siemens.com/index.aspx?Nr=11157

 

[puuukeey]

Are you trying to measure the height of a moving wave in real time?

yes


jraef ,
I called siemens this afternoon and they said that the sampling rate was to low which didn't make much sense to me, but I guess it's digital

 

[roydm]

As an audio engineer you could try this.
Drop a weighted insulated wire into the wave (teflon insulated wire is the best Make sure you insulate the end well or double it back to the surface. Now you have a variable capacitor that is proportional to the immersion depth (one plate is the water, the other the wire.
Use the capacitor in an audio oscillator or some other circuit that will measure the value.
Now you have a capacitance level transmitter. It may not give you the accuracy you asked for but will have very fast response.
If you need more capacitance use more lengths of wire or a probe with large surface area.
Good Luck
Roy

 

[itsmoked]

Nice one Roy.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[sreid]

An ultrasonic type that would probably do the job.

http://www.gavazzionline.com/pdf/UC80CND60AKM1TR.pdf

 

[BigInch]

Why not just make a function from some Airy nth order wave equation and slowly (and/or randomly) vary the wave heights and periods over time and start generating virtual ocean waves? Most near shore waves have a period of 6 to 8 seconds.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

 

[btrueblood]

...wasn't there a HUGE post string awhile back about all the myriad ways to make an electronic liquid level sensor?

 

[puuukeey]

Thank you all so much for so many suggestions. every one is being examined carefully.



As for virtualization, I think it might get low frequencies approximately right, but not the high ones. Also not directly come from nature, chaos, speed boats etc. artsy fartsy crap.

I'm hoping you can hear the tides if I speed it up enough.


Also The idea was dual purpose. Liquid obviously doesn't operate like the skin of a drum or a string. I thought it might be cool to get in an oddly shaped pool and do cannon ball Rhythm tracks!

 

[BigInch]

Ya. I figured you were doing it for the natural aspect, but thought it sounded good anyway.

They're putting some rather realistic physics modeling behind some OGL visual water surface simulations and getting very realistic results, if you're interested.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

 

[OperaHouse]

The oscillator method is easy and commonly used. A friend bought one for the foam filled gas tank of his race car and it was only about $65. They can be made with a dual 555 chip (gasp, can't believe I recommended that) creating a variable pulse width. The RMS value of this is rectified for an analog voltage. A beat frequency method like a metal detector could also be used.