In message , Adrian Brentnall writes
It's a long time ago but, ISTR that Thermistors can be used to detect immersion as their characteristics change with the level of heat dissipation.
regards
The pneumatic versions are simple and reliable. They're still used in many applications. You don't say how deep your well is but I'm assuming it's 100ft max. Lower a small bore pipe of known length down the well. Connect the top to a foot pump via a schrader valve. When you want to know the depth, pump the pump until the pressure wont get any higher. The pressure measures the height of water above the bottom of the tube. There's no need to contantly blow air through the tube unless you want a permanent reading. I doubt that's the case. A measurement once a week to gather data is normally enough. One note, the level will vary depending on whether the pump is running or not. The difference could be a number of feet. The two readings are known as standing level and pupmping level. The difference is an indication of the pumping capacity of your well. It's important to always record the same type of reading and allow time for the level to stabilise from one to the other. If you don't, your data will have a wide scatter band and generally confuse more than educate. Good luck.
John
You still need to use a fixed-width font :-)
So draw the air from the well and pump it back in.
All the other suggestions are complicated, unreliable, expensive or stupid :)
May I suggest having two pulleys and two cords of equal lengths. One has a float on the bottom end and the other has a weight. The cords run over the pulleys and have small equal weights on the ends to keep the cord taut. The height of water in the well is the distance between the weights at the top.
It is still accurate even if the cords stretch or change with temperature, since they should both be affected the same. I would not use a lead weight in drinking water.
Can be even cheaper. A digital car tyre pressure guage will typically read to 0.5PSI.
1PSI = about 2 meters, so 0.5PSI would be 1 meter. A length of aquarium tubing, and an old car foot-pump to pressurise it. 99% of aquarium pumps will not have the pressure capability, most top out at ~2m head.Total cost 10 quid?
and am humbled by the useful responses you all have produced - I am sure there is the solution here - and I am humbled by neglecting to fully describe geometry involved.
FWIW the well is dry-stone construction, about 6ft deep, with difference between max & min levels of about 3ft. As to cleanliness / proneness to contamination, apart from just after I jump in barefooted to clean it it is home to tree & other roots but has been tested by the local authority to have no biologic or other harmful impurity. The well is about 150m from the house with electric pump down there raising water to the house. As to the excellence of the water; after a good snowmelt it tastes better than any commercially available.
Thank you all. Phil
Ahh, Would an ultrasonic tapemeasure be any use?? You'd maybe want to create an easier access to make the mearurements through.
This is what I do and it works perfectly. My well is 20ft deep and my only concern is dropping the measure (there is no fitment for a lanyard).
Even though you have received lots of replies I can't resist commenting (because dealing with water level measurements is the day job).
Most automatic monitoring of levels is done with solid state pressure transducers and data loggers. This sort of equipment can be very precise, but subject to instrumental drift and temperature related fluctuations and needs barometric compensation, which either involves running a vent down to the probe (expensive and humidity problems) or needs a separate barometer (just expensive). I have yet to find a way of setting this sort of system up cheaply, but one can always hope.
Previously we used float driven chart recorders, these just require a float and counterweight, and move a pen as the water level varies. By choosing appropriate gearing between float and pen the sensitivity can be varied. Just before the move to pressure transducers some flaot recorders were equuipped with rotary shaft encoders - I have often thought that the insides of a (non-optical) mouse are essentially a rotary shaft encoder... Similar float driven setups can drive a pinter for manual measurement.
Civil engineers have tended to be keen on bubbler techology to measure water levels, as several people have said it is cheap technology, no batteries required!
Manual measurement of water level usually uses a 'dipper' - a graduated tape with electrical contacts that amkes a circuit when it touches water, sounding a buzzer and/or flashing a light. I would think that the Maplin Water Level alarm
The proper old fashioned field improvisation is to use a weighted, chalked, string. The string is let down to the bottom of the well. The string is then marked. When you pull the string up the chalk will have been washed off the saturated string, so measuring the dry chalk up to your mark gives you depth to water.
Even though the OP has mentioned testing of the well, I would be quite wary of bacterial quality in a shallow well. Stone walls and only 1 metre depth to groundwater gives very little protection against bacterial or protozoan pollutants. If I saw a well like this overseas I would be recommending fencing to exclude domestic animals and an impermeable apron around the well to minimise the chance of surface runoff trckling down the lining, and then I would still want to see disinfection of the water before it was drunk.
Andy McKenzie
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