Water tank level sensor

Weigh it?

You didn't mention the material from which the container is made nor any other limitations.

*-*-*-*-*+dielectric.constant+oscillator+*.switches+movement.*.vibration+ultrasound+Coil.around.*.*+quits.*+*-*-reflects-losses-*-*+*-cannot-get-*-*-inside-*-*-*-tube+zz-zz+Quantam.Research.*.capacitive.sensor.*+qq-qq+*-back-pressure-*-*-*+vv+bubbler

From the blue-sky thinking department:

The air space above the water can form a resonant cavity for sound waves. Perhaps if a microphone was suspended above the maximum water level it would show a peakiness at the resonant frequency. That could then be calibrated to give an approximate free space volume and hence water remaining volume.

Think about how blowing across a bottle part filled with water produces a different note depennding on the water level.

--
Jim Backus running OS/2 Warp 3 & 4, Debian Linux and Win98SE
bona fide replies to j  backus  jita  
demon  co  uk

The simplest is a bubbler tube.

"A low pressure stream of air is bubbled at a constant rate to the bottom of the tank. Back pressure on the bubble tube is measured and will be proportional to the tank level (head pressure). Note that a constant flow rate is required for accuracy. I have used one for level measurement in a flume. The flume was handling waste from a dairy factory, lost of fat, caustic and on occasion acid too. Hence proper material selection for other direct measurement was hard."

This has been discussed at length on the Rev-Ed PICAXE forum:

Do a search for water tank

John

You could buy a low cost wireless commercial unit.

Pete

You could use a float attached to a few digital switches if exact level is unimportant.

Those switches could easily be wired to turn on some small lights or send a signal .

Thanks those prices look interesting.

I would say buy a ultrasonic sensor (20 ft range motorola), a cricket (handy board derivative), line of bright LEDS, and program the cricket to light up the leds based on distance. you could put the leds down the side of the tank and calibrate it accordingly. The total cost would be around 60 used and 150 new. Be fun to learn for you anyways. You would use Interactive C (which is a free download GNU). Hell, if you did it, I would program it for you. Would only take 10 lines of code.

Thanks for the ideas. I could build any one of the suggestions myself but I think I will probably buy a solution. Time is money and all that.

The tank is underground and it would be nice to know if there is enough water in it to make connecting the hose to it worthwhile It's mildly annoying to set up say a lawn sprinkler only to find the water runs out after five mins and I have to move the hose to a tap 30 yards away. Taking the lid off the tan to check first takes several mins and involves a screwdriver, mud etc The pump has an anti run-dry cuttout but I'd also like to avoid relying on that. I could fit a float switch but it would be nice if the level guage could do that aswell.

I quite like the

units that "peter" posted. They have a meter with both a wireless link and a serial port on it for quite a good price.

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