'POT' issues with long cable

[Archangel]

Basically 3 tanks 2K to 5K litre capacity, non-metallic, heights 6 to 8 feet. Having got a quantitative reading from all 3 tanks, there's logic that also controls a pump to keep the levels at a required level.

Unfortunately, yes, I did look at the alternatives you mention and had to discard them for various reasons:

Floats (I assume you mean the kind that is anchored, and has a float connected to a pot): would be difficult to get movement thruought the height of the tank. Also, the ambient humidity would junk it in a short time.

Hall effect or optical would be good, but I need to sense 10 levels in each tank; would be complex/expensive. I even considered an IR scheme with the technique Bruce describes on his site for distance measurement. Not to mention optical encoders with a float.


Yes, power is available, but I think if i could get away with data-over-the-Vcc-line, that would be more elegant. And cheaper than RF.

But first, I'm going to try out Melanie's suggestion about PWM and ADC;



Thanks; I've been trying to achieve this for a long time. If there's any interest on this subject, I'll keep posting my observations on this thread.

I do not know how I missed this post .. . Here is an optical method. Water is a pretty good difuser of light, way better than air, if you make up a vertical pipe with clear lucite pins penetrating the pipe and covered on the pipes inside with black tubing so light will not penetrate from their sides, when they are covered with water the light should be able to enter through the ends, or just use fiber optics. Please, pay no heed to the fact I misspelled TUBES as Tubs in the picture.