AVR-Chat

If a little noise can be tolerated in the sensor input, you can add air to the tube.  As the bubbles leave the end of the tube, they'll bounce the pressure a little.

Some of the advantages are that you can put the gauge at the top of the tank, it's cheap and easy to repair.  If you're measuring water (or similar to water density), use a gauge calibrated in in/h2o and read the depth out directly.

Jeff Engel
Happiness is - positive intake manifold pressure.

--- On Wed, 5/13/09, David Kelly <dkelly@hiwaay.net> wrote:

From: David Kelly <dkelly@hiwaay.net>
Subject: Re: [AVR-Chat] Sensor
To: AVR-Chat@yahoogroups.com
Date: Wednesday, May 13, 2009, 12:51 PM











    
            
            


      
      On Wed, May 13, 2009 at 09:47:39AM -0700, Bruce Parham wrote:

> Sorry, my earlier response was incomplete, just the germ of an idea.

> 

> Since the inverted standpipe is initially filled with air, when the

> liquid level rises, the gas will be compressed allowing liquid to

> enter the tube which will reduce the pressure head. The actual

> pressure measured will depend on the total volume of the tube and the

> amount displace by liquid but will always be less than the pressure at

> the bottom of the tube.

> 

> -- The gas compression correction is left as an exercise for the

> student. --



All to avoid purchase of a sensor which won't be damaged by the liquid?



The compressed air in the inverted standpipe will eventually dissolve

into the liquid. This proposed solution will not work in a static

situation, must be cyclical allowing the air in the standpipe be

refreshed periodically.



-- 

David Kelly N4HHE, dkelly@HiWAAY. net

============ ========= ========= ========= ========= ========= ========= ======

Whom computers would destroy, they must first drive mad.


 

      

    
    
	
	 
	
	








	


	
	


      

[Non-text portions of this message have been removed]

At 06:04 AM 14/05/2009, you wrote:
>it's cheap and easy to repair.

 From the amount of traffic generated by this thread
it is clear that the world DOES NEED a good, reliable,
easy to use water/liquid sensor!!

I went through this a couple of years ago when I got my
rain water tank installed. All the high tech ideas came to
nothing. At the end I got a mechanical gauge from a plumbing
supply shop, a spring, a needle and gauge, some string and a
float.

Then my down pipe got blocked for a few months and thought the
gauge was broken as it was always showing less and less water
even though it had been raining.....


Regards

John Samperi

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