water level measurement circuit
Are you trying to measure the water level in a tank or the water level in the well?
In a water tank, the usual method is to drill two holes in the tank. One at the top and another at the bottom. The holes then connect to plumping elbows. Between the elbow is a piece of plastic hose is connected. (If you use clear tubing, you can see the water level ) To sense this level electrically, copper foil is attached to the tubing in two sections to form a long capacitor. The inside of the tube becomes the dielectric within the capacitor. The dielectric of water is much different that air, so the total capacitance changes with the air level.
For water level in a well, I would suggest trying to do it with a ultrasonic measurement. If you fix a measurement point inside the well and point a ultrasonic sensor down as the water and determine the distance from the sensor point to the top of the water. The greater the distance, the less water in the well.
The magazine, Circuit Cellar, as done several projects on this topic in the past. Do a search on their web site,
www.circellar.com
I have purposely not mentioned the resistance method. This involves pulling electrodes in the water and making resistance measurements. While it works, it requires lots of maintanence due to corrosion.