Measuring how full my tank is
20 January, 2014 - 10:35
It my turn to ask for help :)
I've got this 23,000 litre tank (~5060 gal) out the back of my place which harvests rain water which we can use to run the entire house from. During summer it does run low so we switch back to mains water.
My projects is to measure how much water is in the tank, so can see how much we are using and how much rain is falling to fill it, and to know when to swtich over to mains before we get to low.
As the tank is sealed at the top, with mesh to prevent mosquitos from getting inside, there is no physicall access to the inside the tank, which means ultrasonic measurement is out. I really wanted to play with that too. Instead I was thinking of using a Pressure transducer.
There are two ways I could do this. Wet or Dry.
A dry approach would use a BMP085 which I already happen to have, sealed into the end of a hose. This hose would then be suspended in the air at a height greater than the water in the tank. The other end attached to a tap (pre pump) as the water rises the AIR pressure increases/decreases and I can measure this to determine water volume as in inverse relationship.
The Wet approach is to get a pressure transducer which is simply fitted onto the end of a tap. It works the same way but measures the water pressure directly. I'm more inclined to do this as it feels easier.
A column of water 2.31 feet tall creates 1 pound per square inch (psi) of pressure and my tank is 2.6m high (8.53 feet) which is about 3.6 PSI when full. So I'm thinking a 0-5 PSI water pressure transducer would do the job.
http://www.ebay.com.au/itm/100PSI-Pressure-Transducer-or-Sender-for-Oil-...
But of course not 100psi I've never get a reading !
What do we think? Sounds feasable?
Brett
20 January, 2014 - 16:07
#2
Brett, Not big on physics but
Brett,
Not big on physics but I would think wet measurements is best way to go. Air pressure would be much more susceptible to temp variation and more difficult to compensate as temp would vary very rapidly. Wet pressure would only need a tank temp taken for compensation and would be very slow to react.
Think you would also need atmospheric pressure compensation, this can vary by 0.5psi at least and I think would have a bigger effect the bigger then tank is?
sounds like a nice project though!
Garry
20 January, 2014 - 23:28
#3
pressure sensor
I've used a pressure sensor for this before and it was very acurate, especially with a static volume of water. I'll get the details of the sensor for you. It did give out 4-20mA but was also capable of 0-10V (and 4-20mA is easily converted to a voltage)
Mark
22 January, 2014 - 22:30
#4
pesky insects
I use a hah node with an ultrasonictransducer to monitor level of my 2500litre oil tank it is bloody accurate.
drill 2 holes and seal them so peky insects cannot get in.
http://www.homeautomationhub.com/content/oil-tank-depth-gauge
23 January, 2014 - 19:53
#6
Depth sensor
I had a look at the depth sensor I used before. Yes it will do the job but not exactly cheap. But I suppose one of this type may do if you add an amplifier.
| Attachment | Size |
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| dp_sensor.pdf | 456.71 KB |
16 February, 2014 - 23:57
#7
This may be of use
This may be of use Brett
This looks like the way to go. Fit it on the far side of a tap - then you can fix any leaks at the transducer quite easily. It says that it's linear, so should be easy enough to work with. Some temperature compensation might be needed. A 5V supply can power a roomNode as well as the transducer.
Derek.