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OA47

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Joined: 11/04/2012
Location: Australia
Posts: 911

Posted: 05:38pm 24 Aug 2015

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robert.rozee said

MMAndy said When all else fails try this ...

http://milonetech.com/p/about-etape

now that does raise an interesting idea:

how about a PVC pipe running from near the bottom of the tank to the top, sealed at the top end and open at the bottom. then attach an electronic air pressure sensor to the pipe (somewhere near the top end). when the tank is empty, the pressure sensor will just read normal air pressure, but as the water level in the tank increases the pressure in the pipe will increase in a nice linear fashion.

by my reckoning, the pressure increase would be about 100kPa per 10m of water level.

to allow for leakage of air, you would need to also have some arrangement that every now and then (perhaps each week) pumped a little more air into the pipe - this could be done with any small air pump on a timer, or even a bike tyre pump that you operated by hand once a week. this occasional air flow would also serve to help ensure the bottom end of the pipe remained clear.

cheers,
rob :-)

Rob, this is the method albeit not electronic that I currently use to measure the height of the bore water. The bore is approx. 55m in depth and a 6mm poly tube is run to the bottom and the top attached to a pressure gauge. As you have mentioned the air does escape over time and I need to pump air back into the tube to remove the water before I can take a reading. As with the tanks, I would like to transmit the capacity of each tank wirelessly back to a central readout and the thought of maintaining 5 more airlines does have its drawbacks.
GM
GM

robert.rozee
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Joined: 31/12/2012
Location: New Zealand
Posts: 2294

Posted: 06:18pm 24 Aug 2015

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i'm thinking you could pop one of these inside the top of the pipe:
http://www.ebay.com/itm/221485468940
and attach it to a micromite that transmits the data back to home base.

as for accounting for air leakage, you may be able to do something sneaky using a 'passive' air pump comprising a rigid metal container painted black with one-way valves fitted to a pair of inlet and outlet pipes: at night (when cold) the air inside the tank reduces volume, sucking in new air via the inlet valve. during the day, when heated by sunlight, the air inside expands, pushing excess air out trough the outlet valve and down a short connecting tube to the PVC measuring pipe. the volume of air pumped each day may be small, but quite possibly enough to counteract losses in the system.

i also see ebay has small pumps, intended for blood pressure measuring equipment, for less than $10:
http://www.ebay.com/itm/221661467525

cheers,
rob :-)

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