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[DPRG] Water pressure sensors recomendations?

Subject: [DPRG] Water pressure sensors recomendations?
From: Ed Paradis legomaniac at gmail.com
Date: Mon Apr 9 14:36:08 CDT 2012

In the UTD AUV project, we had luck using normal cheap 'dry gas only'
pressure sensors from Honeywell.  To deal with the water, we placed the
sensor in a sealed container which had a flexible membrane.  The inside of
the contain was filled with mineral oil.

Ok, so we were in school... the actual construction was a PVC pipe cap and
a short length of pipe, about 1.5" in diameter, filled with olive oil from
the kitchen, covered with a normal latex party balloon.  The balloon was
affixed using another cap that had a large hole drilled in it.

It worked well in the pool for a good while, but the latex degraded and it
became a leaky mess.

In retrospect, a piece of polypropylene, epoxed over an opening, with a
fill port and a cap on the back would have been a better way.

The actual sensor was an analog job, in a funny DIP-like package with a
"nipple" on the top side.  It ran off 5 volts and gave us very sensitive
results in measuring our depth down to 10 or 15 feet.  I want to say we
could measure inches.

The great thing about measuring depth is that there is no critical physical
dimension.  10 feet of water in a 1 inch pipe would show the same on a
pressure as 10 feet of water in a swimming pool.  So you could build this
and just drop it in the bottom of any barrel you see fit and it'd tell you
"inches of water above the sensor".

And, BTW, to see the other side of the spectrum, you can buy really nice
pressure sensors from Omega. (omega.com)  They'll run you about $100 -
$150.  But they're stainless steel etc etc.

Ed

On Mon, Apr 9, 2012 at 3:17 PM, -Old Dog- <puppy_dog500 at yahoo.com> wrote:

> Hello All:
>
> While this isn't about robotics, it does fall under automation and
> sensors.
>
> I've installed a rain barrel in my back yard, and am trying to devise a
> solid way to measure how much water is in it. I'd like to do so by placing
> a pressure sensor at the barrel's bottom, then calculating depth based on
> pressure. Can anyone recommend a water pressure sensor, that can (1) be
> submerged, (2) run low level DC voltage and (3) provide a reading between
> the ranges of 1 and 1.1 ATM?
>
> Thanks guys.
> -Martin
>
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>
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