Monitoring Water Level in a Tank

That would be a fun system to reproduce.

The more I think about it, the more it becomes clearer.

The guage was mechanical and had two set points (low and high).

There was a small pump which ran at some point/timed, and the line (from a hazy memory) was 1/4 plastic similar to a fish tank.

If you provide low volume air into the line, it requires x pressure before air flows.

The pressure is relative to the head of liquid above the outlet.

As the tank level drops, the pressure reduces ... air leaks out until the two are balanced.

As the tank refills then the pressure increases and liquid will flow up the line.

If the pump starts then the liquid will be displaced and the same pressure remains.

So if you had a small air pump (fish tank) and a pressure sensor, you should have the basics of a monitoring system.

You just need to calibrate it.

Mark

Hi Mark,

It occurs to me that in hydroponics the water must be aerated before application.  The leaves of a plant have chlorophyll and ATP and stuff to get energy from the sun and split CO2, but the roots respire like an animal or a fungus and are similarly susceptible to asphyxiation.  So roots need water with oxygen dissolved into it, like fishies do.  So, this means that a fishy pump is often already present in this case!

I don't know whether I would have ever transferred this idea from the bathtub!  Thanks, it is probably as practical as it is amusing!  I think this would even work for for relatively viscous liquids.  That was probably an incentive for its use in the petrol industry, that and it seems far less messy to clean up than the linear sensors alluded to up in this thread if we are dealing with a thick, composite, organic liquid.  6AM, and you have already made my day!  It is neat to imagine that you could use the pressure sensor both to monitor the increasing pressure and the relieving, discrete event of the bubble leaving for points beyond.

I don't think gauge pressure sensors cost too much anymore, they were a little dear when they first came out, so this should be a practical, realizable thing in some applications.

Gentleman,

in this project there is no pressures or pumps allowed in the procedure.  The system must operate by gravity.

The water used or leaving the lower tank (see diagram above) is saturating material located under the tank.  the saturation is slow process (The process time is at least six hours. so there is at least 12 readings, when filling the refilling the tank every 30 minutes ).  Evaporation from both open tanks is allowed.  Accuracy is only to 1/8" in readings.

The controller clicks the valve open  until the depth recorded by the sensor is 15 inches then the valve is clicked to close.  The depth data (water level dropping) is then collected by the sensor every 30seconds for 30 minutes.  Then the valve is clicked again to fill the tank back to the 15 inch mark and closes.  The second set of depth data is collected for 30 minutes.  This loop is done 12 times.  The above minutes and depths varies (selected by the tester at the start of the process).  Reading may be taken every second or every minutes, etc.

So, if I guess this rightly, the goal is to test the sorption rate to the material?  I'm guessing what the test is.  When the material is saturated does flow stop?  What moderates the outflow such that monitoring it is informative?

The intent is to see what is the final absorption of the material after six hours ( weight material before test and weight after test, but this is outside the scope of the project).  The flow will not stop for set time which is 90 percent of the time is six hours.  Rarely where we have to set the test time less or more than six hours.

Haytham

Since this seems to be a very tightly controlled 'project' can you enlighten us what is your involvement.

ie Is this part of your practical exam for study, are you assisting someone wanting to carry out these experiments.??

The tank dimensions will make a difference in terms of accuracy, speed of delivery (pressure) and possible solutions.

The fill to 15 inches is simple ...use a float switch.

The level could be done with a float and wire/string that rotates a potentiometer.

There are numerous Arduino data loggers on the internet, as you will find wioth a quick search.

I'd also suggest adding a RTC (Real Time Clock) and you may wish to look at some of the boards that already have this.

http://www.seeedstudio.com/depot/Seeeduino-Stalker-v3-p-1882.html?cPath=6_7

Mark

Don

I have a book on Hydroponics and we were set to do an article (well until the major supplier was busted for selling it for the wrong reasons ).

I'm no expert but the non saturated roots system tends to be favoured more than the total immersion in water.

Various things are measured and if the returning water falls into the collection container, oxygen is imparted just like a stream or river.

The Oil industry require "intrinsically safe" devices, which means various processes to limit the energy available where there is product.

Since air is not an energy source and the pump is a distance away, it requires no testing or proving in order to be used in either diesel or petrol.

Yes electronic pressure sensors are very cheap and readily available now, so this is a project I need to add to my list.

Mark

Mark, this is a test that I routinely do in the lab for clients.  The lab is  my business.  My lab technician has to baby sit the test the entire day.

I can have a minimum wage person watch and record the test, but I cant do that as we engineers market our personal as experienced and professional.

My technician makes more money than myself (like most small businesses).  So I want to cut expenses as I am tired of making minimum wages.

I have been talking with Don regarding this, but it seems he knows too much.  His ideas are just above my head.

I bought several controllers and the e-tape and another sensor, but no dice.

The intent is to see if I can make a professional system out of this test, as I have to describe the tools and devices used in the test.  Now its just a cup, measuring tape and I-phone timer.

Simple is good.  I can do simple.

To get rolling, you could put a clear, rigid plastic tube vertically in your lower reservoir.  Inside the tube you put a cork.  Not a tapered cork, but a cylindrical cork.  Atop that you put a rare-earth magnet, cylindrical, large and polarized at the ends.

http://www.kjmagnetics.com/

Then you get a pair of saturating hall sensors:

http://sensing.honeywell.com/index.php?ci_id=47847

Magnetic Digital Position Hall Effect Sensor ICs

Put one sensor by the top and one by the bottom.  They can be about a quarter-inch away from the magnet and still function.  The magnet is prone to corrosion.  Paint it with plasti-dip or spar varnish or something, maybe Q-dope if you have some laying around.

When the bottom sensor is activated set a flip/flop.  The output goes to the amplifier that actuates the solenoid, this event actuates the valve, opening it.  You could probably contract John Wiltrout for this.  I happen to know he is equipped for this very thing back in his compound in America's Dairyland.

If he is unavailable you could try me or a half-dozen other guys on here, MK could do it, my kid N9VCU could do it and probably needs the money.  IIRC the valve is around a Henry in inductance, but its been a decade since I have played with one.

When the top sensor is actuated the F/F is reset, and the solenoid is de-energized, shutting the valve.

This much would grant your helper a well-deserved sit-down.

You could hang your sensor and computer over this setup later to get your data.

That is as simple as I can imagine.

Gotta go to OHare to pick up a buddy now, traffic be damned.  I'll probably be back lurking this evening.

Since this is a one-off, you could probably just go to ebay for a 'DC solid state relay' to obtain your power switch.  Don't forget to throw in a kickback diode.  Your load is Resistive + Inductive.

Okay

I wanted to be sure I wasn't doing someone homework ...as is often the case on this site.

Can you provide the tank dimensions and possibly the High and Low water levels wrt to the tank bottom.

Can we assume that if you have a very absorbent material, the time could get reduced to 20 mins, rather than making a really long measuring system.??

Don's idea is for a float system.

You could achive the same with http://www.seeedstudio.com/depot/water-level-switch-p-565.html

I know on stock cars they used to slip a cable tie or oring around the shock absorber shaft to measure the amount of travel.

You could use something similar to measure the drop and then calculate the volume.

Would that be a suitable means.

I also have to go but will be back later.

Mark