Well depth sensor

Hello

I’m looking for ideas on how best to construct a cheap (let’s say <50GBP) well depth sensor, hooked up to an ESP32 or similar.

the max depth of the well is 20m. water level is typically between 1 and 8m. The sensor will need to be about 5m from the top of the well, so total wire length will be in the region of 25m. The wiring will be buried in conduits so needs to have some robustness. It will (unfortunately) run close to the live feed for the pump.

I’ve used simple switches in shallower wells with good success. the latest incarnation being two terminal blocks bolted into the inside of a pvc tube with a filter on the bottom, each terminal block having an INOX bolt protruding, wired to a weak pull up and ground.

That works well but I’d like to be measuring depth at 50cm-100cm intervals so there would need to be quite a few wires going down the well length. Which in turn leads me to concerns over inductance.

I’ve thought of pressure transducer and seemingly for £50 something can be acquired - but the well gets very silted up - is this likely to be an issue?

tia
Justin

Sonar ?

possibly?

the well is just over 100cm in diameter. a narrow beam ultrasonic sensor might work, but with the well pump and all the cables and ropes in the well there is a risk of bad measurements. frequent snakes along the horizontal tie-off rod too, which may disturb the orientation of the sensor. Also, are cheap sensors available that go to the required depths? the fleabay ones all seem to max out at 4m.

If you just need a 50 cm resolution, float switches will do. They're cheap and pretty robust.

One common wire plus one for each float switch. No issue with inductance or so, as you just check on or off by sending a small current through them. Just don't make the current too small as you will pick up interference. Lightning may be your biggest enemy here. An Arduino at the well would limit the wires through the conduit.

Ultrasound usually can do 4m, but you will be hitting the sides of your well before that (typical cone is 30°). I have seen ultrasound claiming 10m distance, never tried them.

IR not sure, the furthest distance I know of is the VL53L1X which reaches 4m. LiDAR gets further but is much more expensive, probably overkill.

Finally you may consider the good old pressure tube. Getting it properly airtight may be your biggest challenge with these pressures.