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Water Level Meter

I want to monitor the level of water in our rainwater tank electronically - more specifically via the computer.

My thought is to hang a length of ribbon cable down the side of the (plastic) tank with each 'core' cut shorter than the previous. I care more about a lower level than a higher, so I figure I'll probably cut it in something like a log curve.

Now my plan is to cross the top of every core with a resistor in series and attach one side of the circut to the shortest core and one to the longest. As the water climbs it 'short circuits' each progressive resisitor, thus reducing the over-all resistance. I'd then feed this into an A2D convertor and plug that into the computer.

  • R R R - Water level / Resistance | | | | | --- / 0R | | | | | | | | --- / 1R | | | --- / 2R | | --- / 3R

Does this sound sensible? Is there something obvious I've missed? What value should R be? Should R follow the logarythmic curve so that I attempt to get a straight line in the computer? Or am I better to leave every R equal and (by guestimation+testing) determine a close-enough algorithm in software?

Cheers! Rick Measham

Reply to
Rick Measham
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If you are going to build circuitry to interface to the various wires, then you might like to llok at a project from a few years ago that did the same thins. If think it was Silicon Chip (might have even been EA) Used a sound pulse to measure tan level.IO was serial.

Reply to
Terryc

Have a look at wireless Aquagauge. Low cost, specifically designed for rainwater tanks and available with PC interface

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Watch out for cheap "oil tank" ultrasonic units. They are toys.

Good luck John

Reply to
John

I've looked into this a few times, but then I got a bore and the rainwater tank is full, so I haven't got around to doing anything but I've been looking at 2 options, using pressure:

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Or using resistance via this circuit:
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Otherwise that Electosense stuff looks pretty good.

Reply to
Poxy

Water quality is a factor. Pure water is an insulator. In industry ultrasonics is pretty much the standard. Otherwise you could use a pressure transmitter connected to the bottom of the tank.

Friday

Reply to
Friday

Hi Rick, The rainwater in our tank is has quite a high resistance , nothing shows on the 200K range on the meter and the 2 meg. range does strange things. John Ely.

Reply to
John Ely

G'day John,

Thanks for that (and everyone else too!) .. your info certainly puts a dampener on my plans for world domination. Might have to look at something commercial :-/

Cheers! Rick Measham

Reply to
Rick Measham

I "sort-of" remember that EPE magazine had a design for an ultrasonic distance measuring gizmo that could be used to measure water level - maybe 5 or more years ago.

I tried to find something like that via their web site but did not locate it. I did however find that the September 2006 issue features a Water Level Gauge. My copy of that issue was still wrapped in its bag in my pile of unread magazines. I took a peek and it uses a pressure sensor.

Andy Wood snipped-for-privacy@trap.ozemail.com.au

Reply to
Andy Wood

with that setup using a linear scale will probably give the best results, but depending on how you drive the sensor, using all the same resistor may not give a linear result.

you could get a similar result by just soldering resistors end to end for the sensing element and just using that and the other electrode.

your device will be succeptable to ground loops if you're hooking it to earthed PC, especially if there's an electric pump close to the tank.... so you may nees some sort of isolation somewhere.

you'll need to only run the thing for short durations else the electrodes will corrode.

rainwater water may have an unpredictable resistance.

a capacitative sensor may work better,

Bye. Jasen

Reply to
jasen

Been a long time since I tried it but the trick is probably to use an ac source... around 1kHz should work OK.

A dc source, eg a multimeter, causes sufficient electrolysis for gas bubbles to form on the electrodes... or so goes the theory.

I was involved in monitoring the depth of water bores at one time. IIRC the equipment built for the job was a battery operated flip flop and a milliammeter, in conjunction with a single pair of platinum electrodes, which was raised and lowered by hand. It worked fine so long as algae and the likes didn't accumulate on the insulation between the electrodes. An occasional wipe with silicone helped prevent problems.

May not work without maintenance over a long period of time though.

--
John H
Reply to
John_H

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